1 00:00:03,519 --> 00:00:05,888 >> Earth, a unique planet, 2 00:00:06,523 --> 00:00:08,991 restless and dynamic. 3 00:00:09,059 --> 00:00:12,761 Continents shift and clash, 4 00:00:12,796 --> 00:00:15,864 volcanoes erupt, 5 00:00:15,899 --> 00:00:19,134 glaciers grow and recede-- 6 00:00:19,169 --> 00:00:20,502 titanic forces that are 7 00:00:20,537 --> 00:00:23,606 constantly at work, 8 00:00:23,673 --> 00:00:25,140 leaving a trail of geological 9 00:00:25,175 --> 00:00:27,876 mysteries behind. 10 00:00:27,944 --> 00:00:29,979 One of these mysteries 11 00:00:30,080 --> 00:00:31,413 is centered here 12 00:00:31,481 --> 00:00:35,584 in the Grand Canyon in Arizona. 13 00:00:35,619 --> 00:00:37,286 Close to a billion tons of rock 14 00:00:37,354 --> 00:00:38,787 have been carved out 15 00:00:38,888 --> 00:00:42,958 of the ground. 16 00:00:43,026 --> 00:00:44,126 The canyon left behind 17 00:00:44,160 --> 00:00:45,794 could hold all the river water 18 00:00:45,895 --> 00:00:47,963 on Earth and still be less 19 00:00:48,031 --> 00:00:51,066 than half full. 20 00:00:51,134 --> 00:00:52,434 For more than a century, 21 00:00:52,502 --> 00:00:53,535 scientists have debated 22 00:00:53,603 --> 00:00:56,038 how and when this vast chasm 23 00:00:56,072 --> 00:00:58,841 was created. 24 00:00:58,875 --> 00:01:01,710 And now geologists are 25 00:01:01,778 --> 00:01:03,879 uncovering fresh evidence 26 00:01:03,980 --> 00:01:05,881 of how the Grand Canyon fits 27 00:01:05,982 --> 00:01:07,850 into the ever-evolving story 28 00:01:07,884 --> 00:01:13,187 of "How the Earth Was Made." S02x01 Grand Canyon Original Air Date on November 24, 2009 29 00:01:13,224 --> 00:01:16,959 -- Sync, corrected by elderman -- -- for www.MY-SUBS.com -- 30 00:01:17,060 --> 00:01:20,496 The Grand Canyon... 31 00:01:20,530 --> 00:01:22,064 one of America's most 32 00:01:22,132 --> 00:01:26,869 spectacular natural wonders... 33 00:01:26,936 --> 00:01:29,204 A canyon 18 miles across 34 00:01:29,239 --> 00:01:32,341 at its widest point... 35 00:01:32,409 --> 00:01:35,477 277 miles long... 36 00:01:35,512 --> 00:01:39,682 and more than a mile deep. 37 00:01:39,783 --> 00:01:42,851 It is so vast that it can even 38 00:01:42,886 --> 00:01:48,791 be seen from space. 39 00:01:48,858 --> 00:01:50,592 Although Hell's Canyon in Idaho 40 00:01:50,694 --> 00:01:53,128 is almost half a mile deeper, 41 00:01:53,229 --> 00:01:55,230 and Australia's Capertee Valley 42 00:01:55,298 --> 00:01:57,666 is nearly a mile wider, 43 00:01:57,701 --> 00:01:59,201 the Grand Canyon remains 44 00:01:59,235 --> 00:02:02,137 the most famous of them all. 45 00:02:02,238 --> 00:02:03,405 And it also holds one of 46 00:02:03,473 --> 00:02:05,741 geology's greatest mysteries-- 47 00:02:05,775 --> 00:02:08,310 Just how did the Colorado River, 48 00:02:08,378 --> 00:02:09,478 only a tenth the size 49 00:02:09,512 --> 00:02:11,313 of the Mississippi, 50 00:02:11,414 --> 00:02:14,416 form such a large canyon? 51 00:02:14,484 --> 00:02:15,884 The answer has eluded scientists 52 00:02:15,952 --> 00:02:18,120 for more than a century, 53 00:02:18,154 --> 00:02:19,555 because many of the clues 54 00:02:19,589 --> 00:02:20,956 they normally rely on 55 00:02:21,024 --> 00:02:22,191 have been swept away 56 00:02:22,225 --> 00:02:23,592 by the river's water 57 00:02:23,693 --> 00:02:26,862 over millions of years 58 00:02:26,963 --> 00:02:30,232 or buried by landslides 59 00:02:30,300 --> 00:02:35,037 or destroyed by volcanoes. 60 00:02:35,138 --> 00:02:36,105 >> It seems like we should 61 00:02:36,139 --> 00:02:36,972 understand perfectly 62 00:02:37,040 --> 00:02:38,407 how the Grand Canyon formed. 63 00:02:38,475 --> 00:02:39,675 The problem is, we've lost 64 00:02:39,776 --> 00:02:42,010 a tremendous amount of evidence. 65 00:02:42,011 --> 00:02:42,978 It's like a murder mystery where 66 00:02:43,079 --> 00:02:44,279 most of the evidence is lost. 67 00:02:44,347 --> 00:02:46,081 And so the best we can do 68 00:02:46,182 --> 00:02:47,182 is piece together the evidence 69 00:02:47,250 --> 00:02:48,617 that we have. 70 00:02:48,618 --> 00:02:51,086 >> Even so, slowly but surely, 71 00:02:51,154 --> 00:02:53,622 this geological icon is giving 72 00:02:53,690 --> 00:02:58,260 up its most ancient secrets. 73 00:02:58,328 --> 00:02:59,695 The canyon's richly colored 74 00:02:59,729 --> 00:03:01,330 layers offer scientists 75 00:03:01,364 --> 00:03:02,631 one of the most complete 76 00:03:02,732 --> 00:03:06,101 geological records on Earth. 77 00:03:06,102 --> 00:03:08,070 >> The first concept you have to 78 00:03:08,104 --> 00:03:09,605 get your mind around as you're 79 00:03:09,639 --> 00:03:10,906 thinking about the Grand Canyon 80 00:03:10,974 --> 00:03:12,975 is that the stories told by 81 00:03:13,042 --> 00:03:15,177 the rocks are exceedingly old, 82 00:03:15,178 --> 00:03:17,346 millions and billions of years. 83 00:03:20,683 --> 00:03:21,950 >> Karlstrom and his team 84 00:03:21,985 --> 00:03:23,519 are setting out on a grueling 85 00:03:23,620 --> 00:03:24,820 geology field trip 86 00:03:24,888 --> 00:03:27,523 along the Colorado River. 87 00:03:27,624 --> 00:03:30,626 It won't be an easy ride, 88 00:03:30,727 --> 00:03:33,428 because this 1,450-mile-long 89 00:03:33,496 --> 00:03:37,132 river packs a punch. 90 00:03:37,200 --> 00:03:38,867 More than 800 million gallons 91 00:03:38,968 --> 00:03:40,302 of water can flow down 92 00:03:40,370 --> 00:03:44,673 the Colorado every hour... 93 00:03:44,741 --> 00:03:46,875 more water every second 94 00:03:46,943 --> 00:03:48,510 than the average U.S. household 95 00:03:48,578 --> 00:03:52,648 uses in a year. 96 00:03:52,682 --> 00:03:53,849 Karlstrom is investigating 97 00:03:53,917 --> 00:03:55,417 the ancient history of the land 98 00:03:55,485 --> 00:03:56,585 that was here before 99 00:03:56,686 --> 00:03:59,288 the Grand Canyon even existed. 100 00:03:59,322 --> 00:04:00,455 And for that, he needs 101 00:04:00,490 --> 00:04:04,560 to identify its oldest rocks. 102 00:04:04,594 --> 00:04:06,028 He is following in the footsteps 103 00:04:06,129 --> 00:04:07,529 of pioneer explorer 104 00:04:07,564 --> 00:04:10,632 John Wesley Powell. 105 00:04:10,733 --> 00:04:13,001 In 1869, he was the first man to 106 00:04:13,102 --> 00:04:15,270 successfully ride the Colorado 107 00:04:15,371 --> 00:04:16,705 through the entire length 108 00:04:16,739 --> 00:04:19,007 of the canyon. 109 00:04:19,108 --> 00:04:20,075 >> All of us who work 110 00:04:20,109 --> 00:04:21,543 in the canyon as scientists 111 00:04:21,611 --> 00:04:23,078 admire John Wesley Powell 112 00:04:23,179 --> 00:04:25,013 immensely for his pioneer 113 00:04:25,081 --> 00:04:26,381 and scientific exploration 114 00:04:26,449 --> 00:04:28,016 of the Grand Canyon, 115 00:04:28,084 --> 00:04:29,284 And the questions that he framed 116 00:04:29,352 --> 00:04:30,452 are still questions 117 00:04:30,520 --> 00:04:34,923 that we work on today. 118 00:04:34,991 --> 00:04:36,358 >> One of Powell's discoveries 119 00:04:36,459 --> 00:04:38,060 was these intimidating black 120 00:04:38,094 --> 00:04:39,361 rocks at the very base 121 00:04:39,462 --> 00:04:41,997 of the canyon. 122 00:04:42,098 --> 00:04:42,965 >> Well, we're deep in the Grand 123 00:04:42,999 --> 00:04:44,099 Canyon, right by the Colorado 124 00:04:44,167 --> 00:04:45,734 River. You can see these 125 00:04:45,802 --> 00:04:47,903 spectacular black rocks. 126 00:04:48,004 --> 00:04:49,104 Actually John Wesley Powell 127 00:04:49,172 --> 00:04:51,073 called them ugly black rocks 128 00:04:51,174 --> 00:04:53,141 because for him, these hard 129 00:04:53,176 --> 00:04:54,810 rocks made bad rapids, 130 00:04:54,878 --> 00:04:56,712 and that was harder on his trip. 131 00:04:56,813 --> 00:04:57,546 But for those of us who are 132 00:04:57,647 --> 00:04:59,081 interested in the early history 133 00:04:59,148 --> 00:05:01,083 of Grand Canyon, these rocks 134 00:05:01,184 --> 00:05:03,719 are the bonanza. 135 00:05:03,786 --> 00:05:06,688 >> Powell had no way of dating 136 00:05:06,723 --> 00:05:08,690 these rocks, now identified 137 00:05:08,725 --> 00:05:10,792 as vishnu schist. 138 00:05:10,894 --> 00:05:12,728 All he could conclude 139 00:05:12,795 --> 00:05:13,896 from their appearance was that 140 00:05:13,997 --> 00:05:15,631 they had once been molten 141 00:05:15,698 --> 00:05:18,700 deep underground, but Karlstrom 142 00:05:18,735 --> 00:05:20,736 has an advantage-- 143 00:05:20,803 --> 00:05:21,904 modern instruments that can 144 00:05:21,938 --> 00:05:23,272 accurately date the rocks 145 00:05:23,373 --> 00:05:26,775 by measuring radioactive decay. 146 00:05:26,809 --> 00:05:27,910 And the first step 147 00:05:27,977 --> 00:05:28,977 in figuring out what happened 148 00:05:29,045 --> 00:05:31,079 here in the ancient past 149 00:05:31,147 --> 00:05:32,981 is to record when these rocks 150 00:05:33,082 --> 00:05:36,518 were created. 151 00:05:36,552 --> 00:05:38,987 >> These rocks are about 152 00:05:39,088 --> 00:05:41,456 1.7 billion years old. 153 00:05:41,524 --> 00:05:42,257 It's less than half 154 00:05:42,325 --> 00:05:44,092 of the age of the Earth. 155 00:05:44,160 --> 00:05:45,527 So we have a great story here 156 00:05:45,628 --> 00:05:47,863 in the Grand Canyon of the last 157 00:05:47,897 --> 00:05:48,897 almost 2 billion years 158 00:05:48,965 --> 00:05:51,867 of Earth's history. 159 00:05:51,901 --> 00:05:53,135 >> But Karlstrom needs 160 00:05:53,169 --> 00:05:55,003 more information, 161 00:05:55,071 --> 00:05:56,905 and these ugly black rocks 162 00:05:56,973 --> 00:05:58,607 hold another crucial clue 163 00:05:58,708 --> 00:06:00,075 to what this land looked like 164 00:06:00,176 --> 00:06:02,544 before the canyon was cut. 165 00:06:02,612 --> 00:06:04,613 They can tell him not only 166 00:06:04,681 --> 00:06:06,248 when they were formed, 167 00:06:06,316 --> 00:06:08,450 but also precisely how deep 168 00:06:08,518 --> 00:06:09,718 in the Earth's crust 169 00:06:09,819 --> 00:06:13,255 they were made. 170 00:06:13,356 --> 00:06:14,890 These tiny stones embedded 171 00:06:14,958 --> 00:06:16,425 throughout the ancient boulders 172 00:06:16,526 --> 00:06:18,427 are literally jewels, 173 00:06:18,494 --> 00:06:20,362 garnets that only form 174 00:06:20,430 --> 00:06:22,798 under immense pressure, 175 00:06:22,865 --> 00:06:24,166 the sort of pressure that's 176 00:06:24,233 --> 00:06:26,134 found when layers are crushed 177 00:06:26,169 --> 00:06:27,636 by the weight of millions 178 00:06:27,704 --> 00:06:32,674 of tons of rock on top of them. 179 00:06:32,709 --> 00:06:33,909 >> The silver-bullet clue 180 00:06:33,977 --> 00:06:35,711 is the garnet. 181 00:06:35,812 --> 00:06:37,446 These garnets are the key 182 00:06:37,513 --> 00:06:38,714 to understanding the amount 183 00:06:38,815 --> 00:06:42,451 of rock above us. 184 00:06:42,518 --> 00:06:43,518 >> By analyzing the chemical 185 00:06:43,619 --> 00:06:45,253 structure of the garnet, 186 00:06:45,355 --> 00:06:46,521 in particular its calcium 187 00:06:46,622 --> 00:06:48,490 content, investigators can 188 00:06:48,524 --> 00:06:50,359 determine how much weight of 189 00:06:50,426 --> 00:06:52,627 rock was crushing down upon it 190 00:06:52,695 --> 00:06:55,330 at the moment it was made. 191 00:07:00,770 --> 00:07:01,803 >> In simple terms, 192 00:07:01,871 --> 00:07:03,071 if you analyze the garnet 193 00:07:03,172 --> 00:07:04,606 and you see higher calcium 194 00:07:04,707 --> 00:07:06,875 content of the garnet, 195 00:07:06,976 --> 00:07:07,976 it means you're deeper 196 00:07:08,077 --> 00:07:09,778 into a mountain belt, 197 00:07:09,812 --> 00:07:11,446 more rocks above you. 198 00:07:11,514 --> 00:07:13,048 So we take these garnets 199 00:07:13,082 --> 00:07:14,516 back to the laboratory. 200 00:07:14,584 --> 00:07:16,685 We cut a very thin section. 201 00:07:16,719 --> 00:07:17,886 We put them under 202 00:07:17,987 --> 00:07:19,688 an electron microprobe, 203 00:07:19,756 --> 00:07:21,056 and the scientific result 204 00:07:21,157 --> 00:07:22,724 after this analysis is that 205 00:07:22,859 --> 00:07:25,227 we were 6 miles deep beneath 206 00:07:25,261 --> 00:07:26,395 the surface of the peaks 207 00:07:26,429 --> 00:07:28,130 which were above us, 208 00:07:28,164 --> 00:07:34,036 and that's a long ways. Ha ha. 209 00:07:34,070 --> 00:07:35,670 >> So, nearly 2 billion years 210 00:07:35,705 --> 00:07:38,340 ago, before the canyon evolved, 211 00:07:38,441 --> 00:07:40,042 ancient mountains 6 miles 212 00:07:40,076 --> 00:07:42,778 above sea level stood here, 213 00:07:42,879 --> 00:07:44,346 towering peaks as high 214 00:07:44,414 --> 00:07:47,682 as the modern Himalayas. 215 00:07:47,717 --> 00:07:49,618 Over the next 500 million years, 216 00:07:49,685 --> 00:07:51,686 these mountains were worn away 217 00:07:51,788 --> 00:07:53,121 by the relentless forces 218 00:07:53,156 --> 00:07:56,258 of erosion. Over millennia, 219 00:07:56,325 --> 00:07:58,593 the freezing and thawing of ice 220 00:07:58,661 --> 00:07:59,861 cracked open the rock 221 00:07:59,896 --> 00:08:01,797 of the mountain slopes. 222 00:08:01,864 --> 00:08:03,398 Wind and water carried the rock 223 00:08:03,433 --> 00:08:05,867 debris down towards the oceans, 224 00:08:05,935 --> 00:08:07,502 leaving behind a flat 225 00:08:07,570 --> 00:08:09,504 and featureless plain 226 00:08:09,605 --> 00:08:14,076 with no sign at all of a canyon. 227 00:08:14,143 --> 00:08:16,044 >> Geologists learn to visualize 228 00:08:16,112 --> 00:08:17,746 the way that this place looked 229 00:08:17,780 --> 00:08:20,782 in the past. Knowing how to read 230 00:08:20,883 --> 00:08:22,884 the texture of the rock, 231 00:08:22,952 --> 00:08:24,152 the kind of rock it is, 232 00:08:24,220 --> 00:08:25,520 the fossils that are in it, 233 00:08:25,588 --> 00:08:26,688 geologists can-- 234 00:08:26,756 --> 00:08:27,856 It's like a detective story. 235 00:08:27,890 --> 00:08:29,524 You can uncover what 236 00:08:29,592 --> 00:08:30,859 this place looked like 237 00:08:30,960 --> 00:08:33,328 billions of years ago. 238 00:08:38,935 --> 00:08:41,870 >> This is now desert country, 239 00:08:41,938 --> 00:08:45,707 more than 300 miles inland. 240 00:08:45,775 --> 00:08:47,676 And yet these shells 241 00:08:47,777 --> 00:08:52,114 encased in solid rocks... 242 00:08:52,148 --> 00:08:55,951 are ocean fossils. 243 00:08:56,018 --> 00:08:57,219 >> In this one cliff, 244 00:08:57,286 --> 00:08:58,687 you can find fossil shells 245 00:08:58,788 --> 00:08:59,921 that look like you'd pick up 246 00:08:59,956 --> 00:09:01,857 on the seashore today. 247 00:09:01,924 --> 00:09:02,591 They die, they fall to 248 00:09:02,692 --> 00:09:03,758 the bottom of the sea floor, 249 00:09:03,793 --> 00:09:05,127 and they get trapped 250 00:09:05,194 --> 00:09:07,229 and die in the mud 251 00:09:07,296 --> 00:09:09,131 at the bottom of the ocean 252 00:09:09,232 --> 00:09:10,065 at the time that they're 253 00:09:10,133 --> 00:09:12,601 being deposited. 254 00:09:12,702 --> 00:09:13,768 >> Shells like these come 255 00:09:13,836 --> 00:09:16,605 from shallow, tropical waters, 256 00:09:16,672 --> 00:09:18,773 an inland sea that first arrived 257 00:09:18,841 --> 00:09:21,409 here half a billion years ago 258 00:09:21,511 --> 00:09:22,744 and covered the flat, 259 00:09:22,812 --> 00:09:25,814 low-lying plain. 260 00:09:25,848 --> 00:09:27,082 But that did not happen 261 00:09:27,116 --> 00:09:29,718 just once. Many different layers 262 00:09:29,752 --> 00:09:31,720 in the walls of the Grand Canyon 263 00:09:31,754 --> 00:09:33,188 tell Karlstrom that over 264 00:09:33,256 --> 00:09:35,190 hundreds of millions of years, 265 00:09:35,291 --> 00:09:36,825 this land has been submerged 266 00:09:36,893 --> 00:09:39,361 by the sea not just once, 267 00:09:39,428 --> 00:09:42,564 but at least 8 times. 268 00:09:42,632 --> 00:09:43,532 The last time this part 269 00:09:43,566 --> 00:09:45,267 of Arizona was under the sea 270 00:09:45,301 --> 00:09:49,337 was around 80 million years ago. 271 00:09:49,372 --> 00:09:50,572 >> As we go higher in the layers 272 00:09:50,640 --> 00:09:52,374 in the Grand Canyon, we have 273 00:09:52,441 --> 00:09:54,376 different-aged seas, which are 274 00:09:54,443 --> 00:09:55,810 depositing different kinds of 275 00:09:55,912 --> 00:09:57,279 rocks, different environments, 276 00:09:57,346 --> 00:09:58,613 different fossils that live 277 00:09:58,648 --> 00:10:00,382 at the different times. 278 00:10:00,449 --> 00:10:02,651 This chapter of seas coming in 279 00:10:02,718 --> 00:10:04,986 and seas going out is itself 280 00:10:05,021 --> 00:10:08,356 hundreds of millions of years. 281 00:10:08,424 --> 00:10:09,524 >> Each sea deposited 282 00:10:09,559 --> 00:10:11,560 different types of material that 283 00:10:11,627 --> 00:10:15,830 hardened to become solid rock. 284 00:10:15,898 --> 00:10:17,832 Some sediment was sand that 285 00:10:17,900 --> 00:10:22,204 gecame buff-colored sandstone, 286 00:10:22,271 --> 00:10:24,172 some was mud that hardened 287 00:10:24,273 --> 00:10:27,809 into darker shale, 288 00:10:27,877 --> 00:10:28,910 while the calcified remains 289 00:10:28,978 --> 00:10:31,279 of marine organisms were crushed 290 00:10:31,380 --> 00:10:35,016 into light-colored limestone. 291 00:10:35,084 --> 00:10:37,252 And yet the dominant color 292 00:10:37,286 --> 00:10:39,454 is red. 293 00:10:44,293 --> 00:10:45,627 That comes from iron 294 00:10:45,728 --> 00:10:49,364 locked within all the rocks. 295 00:10:49,432 --> 00:10:51,466 Over millions of years, 296 00:10:51,534 --> 00:10:52,968 the iron rusts into 297 00:10:53,002 --> 00:10:56,738 a distinctive red hue. 298 00:10:56,806 --> 00:10:59,441 For the geology detectives, 299 00:10:59,508 --> 00:11:01,009 descending into the Grand Canyon 300 00:11:01,077 --> 00:11:08,149 is like traveling back itime. 301 00:11:08,251 --> 00:11:09,951 The calcium content inside 302 00:11:10,052 --> 00:11:11,753 garnet gemstones reveals 303 00:11:11,787 --> 00:11:13,888 that nearly 2 billion years ago, 304 00:11:13,956 --> 00:11:14,889 mountains the size 305 00:11:14,957 --> 00:11:16,157 pf Mt. Everest stood 306 00:11:16,225 --> 00:11:20,662 where the Grand Canyon is now. 307 00:11:20,696 --> 00:11:21,930 Sea fossils exposed 308 00:11:21,964 --> 00:11:23,498 in the cliffs show that as late 309 00:11:23,599 --> 00:11:25,600 as 500 million years ago, 310 00:11:25,668 --> 00:11:27,135 the land was the muddy bottom 311 00:11:27,236 --> 00:11:32,974 of an ancient inland sea. 312 00:11:33,042 --> 00:11:35,243 The next puzzle for geologists 313 00:11:35,311 --> 00:11:37,479 is uncovering which awesome 314 00:11:37,513 --> 00:11:39,614 forces transformed that 315 00:11:39,682 --> 00:11:41,316 unremarkable flat land 316 00:11:41,417 --> 00:11:43,485 into this breathtaking 317 00:11:43,519 --> 00:11:47,289 natural wonder of the world. 318 00:11:50,856 --> 00:11:53,224 >> From 1.7 billion years ago 319 00:11:53,292 --> 00:11:55,026 to 70 million years ago, 320 00:11:55,094 --> 00:11:57,028 the landscape of western Arizona 321 00:11:57,096 --> 00:11:58,363 has undergone a series 322 00:11:58,397 --> 00:12:01,566 of extraordinary changes. 323 00:12:01,667 --> 00:12:03,101 Ancient mountains have given way 324 00:12:03,135 --> 00:12:06,137 to prehistoric seas 325 00:12:06,205 --> 00:12:07,572 which have withdrawn to reveal 326 00:12:07,673 --> 00:12:09,407 a low-lying flat plain 327 00:12:09,475 --> 00:12:10,742 stretching as far 328 00:12:10,843 --> 00:12:14,112 as the eye can see. 329 00:12:14,213 --> 00:12:15,079 The magnificent gorge 330 00:12:15,114 --> 00:12:16,447 of the Grand Canyon 331 00:12:16,482 --> 00:12:18,850 does not yet exist 332 00:12:18,951 --> 00:12:20,351 but over the next 20 million 333 00:12:20,386 --> 00:12:22,287 years, this landscape was 334 00:12:22,388 --> 00:12:24,289 to undergo immense changes 335 00:12:24,390 --> 00:12:25,723 that would create a unique 336 00:12:25,758 --> 00:12:28,459 high plateau and set the scene 337 00:12:28,494 --> 00:12:33,298 for the formation of the canyon. 338 00:12:33,365 --> 00:12:35,767 Ancient fossils of sea animals 339 00:12:35,834 --> 00:12:37,635 tell geologists that this land 340 00:12:37,670 --> 00:12:39,270 was once under the waves 341 00:12:39,305 --> 00:12:42,674 of an inland ocean, but that 342 00:12:42,741 --> 00:12:46,811 leads to yet another mystery. 343 00:12:46,845 --> 00:12:47,946 The investigation needs 344 00:12:48,013 --> 00:12:49,747 to figure out why these undersea 345 00:12:49,848 --> 00:12:52,550 rocks are now high in the air, 346 00:12:52,651 --> 00:12:53,851 thousands of feet 347 00:12:53,919 --> 00:12:55,820 above sea level. 348 00:12:55,854 --> 00:12:56,988 >> It's surprising to go up 349 00:12:56,989 --> 00:12:58,923 a mile above sea level, 350 00:12:58,991 --> 00:13:00,825 and you find a clam shell 351 00:13:00,893 --> 00:13:02,827 or what looks like a clam shell, 352 00:13:02,928 --> 00:13:04,662 and you say, "that's what I see 353 00:13:04,663 --> 00:13:05,897 "when I go down to the ocean." 354 00:13:05,931 --> 00:13:06,731 "so why is it here, 355 00:13:06,765 --> 00:13:10,535 a mile above sea level?" 356 00:13:10,569 --> 00:13:12,170 >> It's clear that this region 357 00:13:12,204 --> 00:13:13,638 underwent a type of geological 358 00:13:13,739 --> 00:13:15,940 disturbance that pushed up 359 00:13:16,008 --> 00:13:19,711 the entire seabed. 360 00:13:19,745 --> 00:13:21,379 Geologists discovered 361 00:13:21,480 --> 00:13:23,615 in the 1960's that collisions 362 00:13:23,649 --> 00:13:24,849 between separate plates 363 00:13:24,917 --> 00:13:26,618 of the Earth's crust could 364 00:13:26,652 --> 00:13:29,721 force land up into the air. 365 00:13:29,755 --> 00:13:32,090 It happens all over the globe 366 00:13:32,124 --> 00:13:34,092 and usually deforms the land 367 00:13:34,159 --> 00:13:36,995 into tilted mountain ranges. 368 00:13:37,029 --> 00:13:38,730 But this Arizona uplift 369 00:13:38,797 --> 00:13:40,665 was unique. 370 00:13:40,733 --> 00:13:41,899 >> After all the flat layers 371 00:13:41,934 --> 00:13:43,735 are deposited at sea level, 372 00:13:43,802 --> 00:13:45,169 there was a major uplift event 373 00:13:45,204 --> 00:13:46,904 called the Laramide Orogeny, 374 00:13:46,939 --> 00:13:48,072 which lifted these rocks 375 00:13:48,107 --> 00:13:49,340 without tilting them, 376 00:13:49,375 --> 00:13:51,175 still flat, lifted them up 377 00:13:51,210 --> 00:13:54,178 to high elevation. 378 00:13:54,213 --> 00:13:55,647 >> Because the land rose 379 00:13:55,748 --> 00:13:57,248 straight up, like being 380 00:13:57,282 --> 00:13:59,450 in an elevator, it formed 381 00:13:59,485 --> 00:14:02,987 a high, smooth plateau. 382 00:14:03,022 --> 00:14:04,255 The sea that had been there 383 00:14:04,289 --> 00:14:05,790 drained back toward 384 00:14:05,824 --> 00:14:08,893 the northeast, but as of yet, 385 00:14:08,927 --> 00:14:12,196 there was no Grand Canyon. 386 00:14:12,264 --> 00:14:13,731 The Colorado River, the force 387 00:14:13,832 --> 00:14:15,466 that cut the canyon from 388 00:14:15,567 --> 00:14:18,636 the rock, had yet to arrive. 389 00:14:20,906 --> 00:14:22,106 >> Geologists, from the very 390 00:14:22,174 --> 00:14:23,975 early days, from the late 1800's 391 00:14:24,009 --> 00:14:25,176 are quite comfortable 392 00:14:25,277 --> 00:14:26,477 with the knowledge 393 00:14:26,545 --> 00:14:27,445 that the Colorado River 394 00:14:27,479 --> 00:14:29,614 has carved the Grand Canyon. 395 00:14:29,648 --> 00:14:30,982 [thunder] 396 00:14:31,016 --> 00:14:32,016 >> The high plateau was 397 00:14:32,084 --> 00:14:33,651 surrounded by even higher 398 00:14:33,719 --> 00:14:35,720 mountain ranges. 399 00:14:35,821 --> 00:14:37,255 New rivers began flowing 400 00:14:37,289 --> 00:14:38,656 from the mountains 401 00:14:38,724 --> 00:14:41,459 out across the plateau. 402 00:14:41,527 --> 00:14:42,827 It's essential for 403 00:14:42,895 --> 00:14:44,562 the investigation to establish 404 00:14:44,630 --> 00:14:46,330 when the Colorado River, 405 00:14:46,365 --> 00:14:48,332 in particular, arrived, 406 00:14:48,367 --> 00:14:50,635 because only then could it 407 00:14:50,703 --> 00:14:55,873 begin to carve the canyon. 408 00:14:55,908 --> 00:14:58,076 Until a few decades ago, 409 00:14:58,110 --> 00:14:59,277 some investigators thought 410 00:14:59,378 --> 00:15:01,179 this ancient riverbed 411 00:15:01,246 --> 00:15:02,647 called Hindu Canyon 412 00:15:02,715 --> 00:15:04,882 provided the answer. 413 00:15:04,917 --> 00:15:07,185 They believed that Hindu 414 00:15:07,286 --> 00:15:09,721 Canyon's creation 50 million 415 00:15:09,788 --> 00:15:11,923 years ago marked the arrival 416 00:15:11,990 --> 00:15:14,192 of the Colorado River 417 00:15:14,259 --> 00:15:15,359 and the beginnings 418 00:15:15,461 --> 00:15:18,463 of the Grand Canyon. 419 00:15:18,530 --> 00:15:21,999 But in 1969, the discovery 420 00:15:22,101 --> 00:15:24,102 of these pebbles turned 421 00:15:24,169 --> 00:15:25,603 everything that geologists 422 00:15:25,637 --> 00:15:26,738 thought they knew about 423 00:15:26,805 --> 00:15:30,441 the canyon on its head. 424 00:15:30,442 --> 00:15:31,909 >> It turns out that to explain 425 00:15:32,010 --> 00:15:33,377 how the Grand Canyon got there 426 00:15:33,445 --> 00:15:34,812 is very much more complex 427 00:15:34,880 --> 00:15:36,013 than people thought. 428 00:15:36,014 --> 00:15:37,281 So the early geologists 429 00:15:37,349 --> 00:15:38,182 thought it was simple, 430 00:15:38,283 --> 00:15:39,350 but now we realize there's 431 00:15:39,418 --> 00:15:40,618 a lot more to the story, and 432 00:15:40,719 --> 00:15:42,720 it's kind of a detective story. 433 00:15:42,788 --> 00:15:44,188 You start out with a few clues, 434 00:15:44,256 --> 00:15:45,623 and you put the clues together, 435 00:15:45,724 --> 00:15:47,058 and then finally you get 436 00:15:47,092 --> 00:15:48,359 the satisfaction of saying, 437 00:15:48,460 --> 00:15:49,327 "well, you know, I figured this 438 00:15:49,361 --> 00:15:52,330 out before anybody else did." 439 00:15:52,364 --> 00:15:53,231 >> Figuring it out 440 00:15:53,332 --> 00:15:54,699 before anyone else was just 441 00:15:54,767 --> 00:15:57,301 what Young did in 1969, 442 00:15:57,336 --> 00:15:58,402 when he was a 24-year-old 443 00:15:58,470 --> 00:16:00,505 geology graduate student 444 00:16:00,572 --> 00:16:02,940 at Washington University. 445 00:16:02,975 --> 00:16:05,042 His professor sent him 446 00:16:05,144 --> 00:16:07,478 to investigate Hindu Canyon. 447 00:16:07,513 --> 00:16:09,046 But when Toung arrived 448 00:16:09,148 --> 00:16:10,581 at the dusty riverbed, 449 00:16:10,682 --> 00:16:11,783 he discovered that it had 450 00:16:11,850 --> 00:16:13,518 nothing to do with the Colorado 451 00:16:13,585 --> 00:16:18,289 or the Grand Canyon itself. 452 00:16:18,323 --> 00:16:20,391 His discovery flew in the face 453 00:16:20,425 --> 00:16:21,859 of all the established 454 00:16:21,927 --> 00:16:23,594 geological theories 455 00:16:23,662 --> 00:16:25,763 and revolutionized thinking 456 00:16:25,864 --> 00:16:29,033 about the canyon's history. 457 00:16:29,134 --> 00:16:30,868 The evidence Young had uncovered 458 00:16:30,969 --> 00:16:32,770 was the alignment of pebbles 459 00:16:32,838 --> 00:16:35,773 in the bed of the river. 460 00:16:35,874 --> 00:16:37,308 >> Look at these pebbles. 461 00:16:37,376 --> 00:16:38,943 You can see that the pebbles 462 00:16:39,011 --> 00:16:41,012 are flowing, or the pebbles 463 00:16:41,046 --> 00:16:42,513 are arrayed in this direction, 464 00:16:42,614 --> 00:16:44,048 which is a stable direction 465 00:16:44,116 --> 00:16:46,684 for water flowing to my right. 466 00:16:46,785 --> 00:16:47,919 If the pebbles had been 467 00:16:47,953 --> 00:16:49,220 oriented this way, the water 468 00:16:49,288 --> 00:16:50,755 would have flipped them over. 469 00:16:50,823 --> 00:16:51,823 So when we find pebbles 470 00:16:51,857 --> 00:16:53,224 that are oriented this way, 471 00:16:53,325 --> 00:16:54,492 that tells us that the water 472 00:16:54,593 --> 00:16:57,662 was flowing to my right. 473 00:16:57,696 --> 00:17:00,331 >> It is a crucial clue. 474 00:17:00,399 --> 00:17:01,666 The Colorado River could never 475 00:17:01,767 --> 00:17:04,035 have flowed to Young's right. 476 00:17:04,136 --> 00:17:05,102 It has always run 477 00:17:05,137 --> 00:17:06,671 in the opposite direction, 478 00:17:06,738 --> 00:17:09,574 towards the Pacific Ocean. 479 00:17:09,641 --> 00:17:11,108 The river here, 50 million 480 00:17:11,143 --> 00:17:14,045 years ago, was not the Colorado, 481 00:17:14,112 --> 00:17:16,414 and it did not cut 482 00:17:16,481 --> 00:17:19,951 the Grand Canyon. 483 00:17:20,052 --> 00:17:21,853 Young's findings meant 484 00:17:21,920 --> 00:17:24,021 scientists had to rethink 485 00:17:24,122 --> 00:17:25,656 all their ideas about when 486 00:17:25,757 --> 00:17:27,091 the Colorado had arrived 487 00:17:27,125 --> 00:17:29,393 on the plateau and about 488 00:17:29,461 --> 00:17:33,764 the age of the canyon. 489 00:17:33,832 --> 00:17:35,233 They started examining evidence 490 00:17:35,300 --> 00:17:39,136 from another less-ancient site. 491 00:17:39,204 --> 00:17:41,105 This is Muddy Creek, 492 00:17:41,139 --> 00:17:43,474 near Lake Mead, Arizona, 493 00:17:43,542 --> 00:17:45,109 just a few miles downstream 494 00:17:45,210 --> 00:17:46,677 from where the Colorado River 495 00:17:46,745 --> 00:17:50,014 exits the Grand Canyon today. 496 00:17:54,119 --> 00:17:55,753 The underlying rocks prove 497 00:17:55,854 --> 00:17:57,588 that this was once the site 498 00:17:57,656 --> 00:18:01,926 of a vast freshwater lake. 499 00:18:01,994 --> 00:18:02,827 >> The upper part of the Muddy 500 00:18:02,861 --> 00:18:04,095 Creek formation is this nice 501 00:18:04,129 --> 00:18:05,029 limestone, which formed 502 00:18:05,130 --> 00:18:06,464 in a freshwater lake. 503 00:18:06,498 --> 00:18:07,632 The water would have been 504 00:18:07,666 --> 00:18:08,633 very clean. There would have 505 00:18:08,667 --> 00:18:09,767 been lots of plants and animals 506 00:18:09,835 --> 00:18:10,835 living in the water. 507 00:18:10,936 --> 00:18:12,403 And as they sank to the bottom, 508 00:18:12,471 --> 00:18:13,271 the calcium carbonate 509 00:18:13,305 --> 00:18:14,572 in their shells would form 510 00:18:14,673 --> 00:18:15,840 this limestone, which is 511 00:18:15,908 --> 00:18:17,842 typically what forms 512 00:18:17,910 --> 00:18:20,478 the limestone rock. 513 00:18:20,545 --> 00:18:21,445 >> The limestone 514 00:18:21,480 --> 00:18:22,847 is the calcified remains 515 00:18:22,948 --> 00:18:24,181 of the creatures that once 516 00:18:24,216 --> 00:18:26,717 lived in this lake. 517 00:18:26,752 --> 00:18:29,720 Then 5.5 million years ago, 518 00:18:29,755 --> 00:18:32,356 the animals all disappeared. 519 00:18:32,391 --> 00:18:33,557 There were no shells 520 00:18:33,659 --> 00:18:36,360 to make fresh limestone. 521 00:18:36,361 --> 00:18:38,362 The only explanation 522 00:18:38,463 --> 00:18:40,097 is that the animals died 523 00:18:40,165 --> 00:18:42,166 5.5 million years ago 524 00:18:42,267 --> 00:18:43,734 because that was the date 525 00:18:43,802 --> 00:18:45,236 when the Colorado River 526 00:18:45,270 --> 00:18:47,271 arrived here. 527 00:18:47,339 --> 00:18:48,239 The river would have been 528 00:18:48,273 --> 00:18:49,640 carrying masses of dirt 529 00:18:49,708 --> 00:18:50,875 and rock sediment 530 00:18:50,909 --> 00:18:54,278 from the fledgling Grand Canyon. 531 00:18:54,346 --> 00:18:55,980 >> The water would have been 532 00:18:56,081 --> 00:18:57,548 too muddy and dirty, 533 00:18:57,616 --> 00:18:58,983 and limestone does not form 534 00:18:59,051 --> 00:19:01,052 in dirty, silty, muddy water. 535 00:19:01,086 --> 00:19:02,887 It's just incompatible. 536 00:19:02,988 --> 00:19:03,788 The animals and plants 537 00:19:03,822 --> 00:19:05,089 that live in such a lake 538 00:19:05,157 --> 00:19:06,090 can't exist if there's a lot 539 00:19:06,158 --> 00:19:09,427 of silt and mud in the water. 540 00:19:09,461 --> 00:19:11,362 >> So the muddy death 541 00:19:11,430 --> 00:19:12,964 of the lake gave geologists 542 00:19:12,998 --> 00:19:14,699 a confirmed date for when 543 00:19:14,800 --> 00:19:17,335 the Colorado arrived in Arizona 544 00:19:17,369 --> 00:19:20,604 and commenced its excavations. 545 00:19:20,639 --> 00:19:21,906 The Grand Canyon was born 546 00:19:21,974 --> 00:19:27,611 a mere 5.5 million years ago. 547 00:19:27,713 --> 00:19:28,879 The investigation has reached 548 00:19:28,981 --> 00:19:31,582 a significant milestone. 549 00:19:31,616 --> 00:19:33,250 It has discovered the age 550 00:19:33,318 --> 00:19:37,421 of the canyon. 551 00:19:37,456 --> 00:19:38,789 The angle at which pebbles lie 552 00:19:38,890 --> 00:19:40,491 in ancient riverbeds reveal 553 00:19:40,525 --> 00:19:41,792 that the Grand Canyon 554 00:19:41,893 --> 00:19:43,861 is far younger than geologists 555 00:19:43,895 --> 00:19:48,232 had previously ever suspected. 556 00:19:48,266 --> 00:19:50,267 The limestone discovered 557 00:19:50,335 --> 00:19:52,503 at Muddy Creek reveals the date 558 00:19:52,537 --> 00:19:54,038 that the Colorado River 559 00:19:54,072 --> 00:19:55,806 arrived on the plateau 560 00:19:55,874 --> 00:19:58,442 and the true age of the canyon-- 561 00:19:58,510 --> 00:20:01,979 5.5 million years old. 562 00:20:02,047 --> 00:20:04,348 Now geologists had 563 00:20:04,449 --> 00:20:06,684 a new mystery to solve-- 564 00:20:06,718 --> 00:20:07,985 discovering why the Colorado 565 00:20:08,053 --> 00:20:09,954 River took the path it did 566 00:20:09,988 --> 00:20:12,623 some 5.5 million years ago 567 00:20:12,691 --> 00:20:14,525 and why it carved a canyon 568 00:20:14,626 --> 00:20:17,628 of such remarkable dimensions. 569 00:20:20,077 --> 00:20:21,177 >> The investigation into 570 00:20:21,245 --> 00:20:22,712 the history of the Grand Canyon 571 00:20:22,780 --> 00:20:24,447 has uncovered a 1.7 billion 572 00:20:24,515 --> 00:20:26,182 year old landscape that has 573 00:20:26,250 --> 00:20:28,618 evolved from ancient mountains 574 00:20:28,685 --> 00:20:31,721 through to the Colorado plateau. 575 00:20:31,789 --> 00:20:33,990 5.5 million years ago, 576 00:20:34,057 --> 00:20:35,525 the Colorado River began 577 00:20:35,626 --> 00:20:37,693 carving out the Grand Canyon 578 00:20:37,795 --> 00:20:40,429 from this plateau. 579 00:20:40,497 --> 00:20:41,430 The question scientists 580 00:20:41,532 --> 00:20:42,799 now had to answer was 581 00:20:42,866 --> 00:20:44,433 what happened at that time 582 00:20:44,501 --> 00:20:46,669 yo cause the river to dig deep 583 00:20:46,703 --> 00:20:49,906 and carve out the canyon. 584 00:20:49,973 --> 00:20:52,141 It is a debate that has been 585 00:20:52,176 --> 00:20:54,577 going on for more than a century 586 00:20:54,611 --> 00:20:58,514 and which continues today. 587 00:20:58,582 --> 00:20:59,215 >> I got interested 588 00:20:59,249 --> 00:21:00,349 in the Grand Canyon 589 00:21:00,417 --> 00:21:01,350 when I went to school 590 00:21:01,351 --> 00:21:03,052 and started studying, 591 00:21:03,086 --> 00:21:03,786 and I heard about 592 00:21:03,887 --> 00:21:04,720 the different ideas associated 593 00:21:04,788 --> 00:21:05,888 with the Grand Canyon and was 594 00:21:05,989 --> 00:21:07,757 just blown away when I found out 595 00:21:07,758 --> 00:21:08,958 we did not understand 596 00:21:08,992 --> 00:21:10,893 how the Grand Canyon formed. 597 00:21:10,961 --> 00:21:11,761 That something as iconic 598 00:21:11,795 --> 00:21:12,895 as the Grand Canyon wasn't 599 00:21:12,963 --> 00:21:14,430 understood just seemed crazy 600 00:21:14,531 --> 00:21:16,332 to me, and so I basically 601 00:21:16,400 --> 00:21:17,500 decided to dedicate 602 00:21:17,534 --> 00:21:18,701 a large portion of my life 603 00:21:18,769 --> 00:21:20,603 to trying to figure it out. 604 00:21:20,704 --> 00:21:22,805 >> One theory is that several 605 00:21:22,873 --> 00:21:24,807 ancient rivers merged, 606 00:21:24,875 --> 00:21:26,409 and their combined cutting power 607 00:21:26,443 --> 00:21:29,512 started digging out the canyon. 608 00:21:29,580 --> 00:21:31,714 Another assumes that the river 609 00:21:31,782 --> 00:21:33,716 cut down into the plateau 610 00:21:33,784 --> 00:21:37,620 as the land uplifted around it. 611 00:21:37,688 --> 00:21:39,155 But John Douglass has 612 00:21:39,223 --> 00:21:40,790 his own theory, one that has 613 00:21:40,891 --> 00:21:42,325 gained respect among many 614 00:21:42,426 --> 00:21:43,693 leading geologists since 615 00:21:43,760 --> 00:21:45,261 he first published his ideas 616 00:21:45,329 --> 00:21:49,432 in 2000. What Douglass calls 617 00:21:49,533 --> 00:21:51,334 his "spillover theory" 618 00:21:51,401 --> 00:21:55,238 seems to work well on paper. 619 00:21:55,305 --> 00:21:56,439 >> Spillover is incredibly easy. 620 00:21:56,506 --> 00:21:57,773 All it means is the Colorado 621 00:21:57,875 --> 00:22:00,343 River poured into a basin. 622 00:22:00,410 --> 00:22:01,978 When it poured into that basin, 623 00:22:02,045 --> 00:22:03,579 it had to form a lake, 624 00:22:03,614 --> 00:22:05,514 and this lake was huge. 625 00:22:05,616 --> 00:22:07,416 All that lake had to do was rise 626 00:22:07,517 --> 00:22:09,685 and spill across the plateau. 627 00:22:09,786 --> 00:22:12,889 It poured down, cutting rapidly, 628 00:22:12,956 --> 00:22:14,390 and over time, you would have 629 00:22:14,424 --> 00:22:15,791 ended up the beginnings 630 00:22:15,893 --> 00:22:18,327 of Grand Canyon very quickly. 631 00:22:18,395 --> 00:22:19,662 >> At his college campus 632 00:22:19,696 --> 00:22:21,664 in Phoenix, Douglass is building 633 00:22:21,698 --> 00:22:23,599 a scale model experiment to see 634 00:22:23,667 --> 00:22:24,867 if his spillover theory 635 00:22:24,968 --> 00:22:27,937 actually works in real life. 636 00:22:27,971 --> 00:22:30,506 He sculpts tons of dirt into 637 00:22:30,607 --> 00:22:34,043 a model of the Colorado plateau. 638 00:22:34,144 --> 00:22:35,411 Running faucets represent 639 00:22:35,479 --> 00:22:37,413 the flow of the Colorado River 640 00:22:37,481 --> 00:22:40,750 into the ancient lake. 641 00:22:40,784 --> 00:22:43,886 >> Now we have our large lake. 642 00:22:43,954 --> 00:22:45,521 The water's getting higher. 643 00:22:45,555 --> 00:22:46,522 It's getting ready to spill 644 00:22:46,590 --> 00:22:48,758 across. We have a tiny little 645 00:22:48,792 --> 00:22:50,026 trickle of water pouring down 646 00:22:50,060 --> 00:22:51,961 off the lake. 647 00:22:52,029 --> 00:22:52,929 That little tiny trickle 648 00:22:52,963 --> 00:22:54,230 of water doesn't seem like much, 649 00:22:54,298 --> 00:22:55,431 but over time, that little bit 650 00:22:55,499 --> 00:22:57,333 of water flowing down that steep 651 00:22:57,401 --> 00:22:59,502 slope is going to gain energy, 652 00:22:59,569 --> 00:23:00,403 it's going to start cutting, 653 00:23:00,504 --> 00:23:02,038 making waterfalls that work 654 00:23:02,105 --> 00:23:04,774 their way back. One waterfall 655 00:23:04,841 --> 00:23:06,409 has now reached the lake. 656 00:23:06,510 --> 00:23:07,877 You can see that we have 657 00:23:07,945 --> 00:23:09,145 just released a significant 658 00:23:09,246 --> 00:23:10,513 amount of water, much more water 659 00:23:10,580 --> 00:23:11,580 than was previously 660 00:23:11,648 --> 00:23:13,215 pouring down. 661 00:23:13,317 --> 00:23:15,151 Now we have huge canyon-cutting. 662 00:23:15,218 --> 00:23:16,786 Landslides are sloughing off 663 00:23:16,853 --> 00:23:18,220 the side of the canyon walls 664 00:23:18,322 --> 00:23:19,055 into the water, flushing it 665 00:23:19,122 --> 00:23:20,589 downstream. The lake, 666 00:23:20,657 --> 00:23:21,691 you can see that it's starting 667 00:23:21,758 --> 00:23:23,192 to shrink in size. 668 00:23:23,226 --> 00:23:25,127 That lake is getting lower. 669 00:23:25,228 --> 00:23:26,329 And right there, you can see 670 00:23:26,396 --> 00:23:27,596 that we have cut our own 671 00:23:27,664 --> 00:23:28,965 small-scale version 672 00:23:29,032 --> 00:23:31,133 of the Grand Canyon. 673 00:23:36,506 --> 00:23:38,574 >> Douglass' experiment proves 674 00:23:38,675 --> 00:23:41,110 that the spillover theory works 675 00:23:41,144 --> 00:23:43,145 in miniature, but he needs 676 00:23:43,213 --> 00:23:44,513 evidence to show that it could 677 00:23:44,581 --> 00:23:46,415 have happened on an infinitely 678 00:23:46,483 --> 00:23:49,685 bigger scale. 679 00:23:49,753 --> 00:23:50,920 Douglass sets out in search 680 00:23:50,954 --> 00:23:52,788 of a lake large enough 681 00:23:52,856 --> 00:23:55,558 and old enough to be the source 682 00:23:55,592 --> 00:23:59,028 of his spillover flood. 683 00:23:59,129 --> 00:24:03,132 He has a prime suspect in mind. 684 00:24:03,233 --> 00:24:04,767 This is the site of the ancient 685 00:24:04,868 --> 00:24:07,236 Lake Bidahochi, 100 miles 686 00:24:07,304 --> 00:24:10,840 to the east of the Grand Canyon. 687 00:24:10,874 --> 00:24:12,508 And a clue here on the old 688 00:24:12,576 --> 00:24:14,410 lakebed reveals how deep 689 00:24:14,478 --> 00:24:18,114 this lake once was. 690 00:24:18,215 --> 00:24:19,782 >> These green clays, 691 00:24:19,850 --> 00:24:22,184 which indicate deep lake water, 692 00:24:22,219 --> 00:24:23,319 this is the classic evidence 693 00:24:23,387 --> 00:24:24,854 for the giant lake necessary 694 00:24:24,921 --> 00:24:26,689 for the overflow explanation 695 00:24:26,757 --> 00:24:28,924 of Grand Canyon. 696 00:24:28,959 --> 00:24:30,393 >> These green deposits 697 00:24:30,494 --> 00:24:31,660 are only created 698 00:24:31,762 --> 00:24:35,664 in one specific environment. 699 00:24:35,732 --> 00:24:36,832 >> To have green lake clays, 700 00:24:36,867 --> 00:24:38,000 you need deeper water, 701 00:24:38,068 --> 00:24:39,902 where there is little oxidation. 702 00:24:39,970 --> 00:24:40,803 I think that's an indication 703 00:24:40,904 --> 00:24:41,737 that the Colorado River 704 00:24:41,805 --> 00:24:43,005 has arrived in this basin, 705 00:24:43,106 --> 00:24:43,806 that it's made its way 706 00:24:43,907 --> 00:24:44,740 from the Rocky Mountains 707 00:24:44,808 --> 00:24:46,442 to this location, and this is 708 00:24:46,543 --> 00:24:47,810 its basically stopover point 709 00:24:47,878 --> 00:24:48,978 before it eventually spills 710 00:24:49,012 --> 00:24:54,817 across to form the Grand Canyon. 711 00:24:54,885 --> 00:25:09,532 >> Establishing the depth 712 00:25:09,599 --> 00:25:12,001 that Lake Bidahochi once spread 713 00:25:12,102 --> 00:25:14,236 over 20,000 square miles 714 00:25:14,271 --> 00:25:16,238 and contained more than 3,000 715 00:25:16,273 --> 00:25:18,707 cubic miles of water. 716 00:25:18,809 --> 00:25:20,076 That makes it bigger 717 00:25:20,177 --> 00:25:22,778 than Lake Michigan. 718 00:25:26,716 --> 00:25:28,184 Douglas needs to date 719 00:25:28,251 --> 00:25:30,319 the age of this lake. 720 00:25:30,353 --> 00:25:31,720 For his spillover theory 721 00:25:31,788 --> 00:25:33,155 to work, it has to be older 722 00:25:33,190 --> 00:25:34,723 than the Grand Canyon, 723 00:25:34,791 --> 00:25:38,694 more than 5.5 million years. 724 00:25:38,728 --> 00:25:41,363 He unearths the proof he needs 725 00:25:41,431 --> 00:25:44,366 in these deep-water fossils. 726 00:25:44,434 --> 00:25:47,436 >> Ok. These fossil shells 727 00:25:47,504 --> 00:25:49,638 are freshwater mollusks 728 00:25:49,706 --> 00:25:51,540 maybe as young as 6 million 729 00:25:51,608 --> 00:25:53,709 years old. 730 00:25:53,777 --> 00:25:55,811 >> The dates match up. 731 00:25:55,879 --> 00:25:56,979 The lake was here at the right 732 00:25:57,047 --> 00:25:58,714 time to have spilled over 733 00:25:58,782 --> 00:25:59,615 and begun cutting 734 00:25:59,683 --> 00:26:01,450 the Grand Canyon. 735 00:26:01,551 --> 00:26:02,785 Dating the fossils helped 736 00:26:02,819 --> 00:26:04,720 confirm Douglass' belief. 737 00:26:04,821 --> 00:26:06,055 But his search for more 738 00:26:06,089 --> 00:26:09,792 evidence continues. 739 00:26:09,860 --> 00:26:10,793 >> In reality, we're never 740 00:26:10,894 --> 00:26:11,794 going to know how it formed 741 00:26:11,895 --> 00:26:13,229 to 100% certainty, unless 742 00:26:13,263 --> 00:26:15,331 someone builds a time machine. 743 00:26:15,365 --> 00:26:16,432 By doing this kind of work, 744 00:26:16,500 --> 00:26:17,333 all you're trying to do 745 00:26:17,367 --> 00:26:18,367 is increase your level 746 00:26:18,435 --> 00:26:19,902 of confidence on your ideas, 747 00:26:20,003 --> 00:26:20,903 build up your case, 748 00:26:20,971 --> 00:26:23,606 build up your evidence. 749 00:26:23,640 --> 00:26:25,040 >> Building up his evidence 750 00:26:25,108 --> 00:26:26,942 is exactly what Joel Pederson 751 00:26:27,043 --> 00:26:29,311 is doing. He is using 752 00:26:29,412 --> 00:26:31,213 the very latest technology 753 00:26:31,281 --> 00:26:32,681 to prove exactly how fast 754 00:26:32,749 --> 00:26:35,384 the Grand Canyon was carved. 755 00:26:35,418 --> 00:26:37,086 He has found the evidence 756 00:26:37,154 --> 00:26:38,787 he needs right here 757 00:26:38,822 --> 00:26:40,022 at the very start 758 00:26:40,090 --> 00:26:42,458 of the Grand Canyon. 759 00:26:42,526 --> 00:26:43,192 >> Here at Lee's Ferry, 760 00:26:43,260 --> 00:26:44,527 there are all of these gravels 761 00:26:44,528 --> 00:26:45,828 that are evidence of where 762 00:26:45,896 --> 00:26:47,463 the river has been in the past 763 00:26:47,531 --> 00:26:48,531 and the path it has taken 764 00:26:48,565 --> 00:26:50,065 during incision, 765 00:26:50,066 --> 00:26:51,200 and amongst the gravels, 766 00:26:51,268 --> 00:26:52,168 sometimes you see 767 00:26:52,202 --> 00:26:54,270 these great lenses of sand, 768 00:26:54,371 --> 00:26:55,838 and we can use the sand 769 00:26:55,906 --> 00:26:57,806 to get an absolute date 770 00:26:57,841 --> 00:27:00,643 on these deposits. 771 00:27:04,080 --> 00:27:05,748 >> As the Colorado River 772 00:27:05,815 --> 00:27:07,283 carved out the canyon, 773 00:27:07,384 --> 00:27:08,717 it deposited more and more 774 00:27:08,785 --> 00:27:10,619 of the gravel and sand debris 775 00:27:10,654 --> 00:27:13,622 at this spot. Newer layers 776 00:27:13,657 --> 00:27:15,157 buried older layers 777 00:27:15,192 --> 00:27:17,693 over millions of years. 778 00:27:17,727 --> 00:27:19,328 And geologists now have 779 00:27:19,362 --> 00:27:21,163 instruments that can measure how 780 00:27:21,198 --> 00:27:22,898 light has affected individual 781 00:27:22,966 --> 00:27:25,100 atoms within the sand. 782 00:27:25,168 --> 00:27:26,702 That reveals precisely 783 00:27:26,736 --> 00:27:28,370 when each sand layer 784 00:27:28,471 --> 00:27:30,272 was originally buried, 785 00:27:30,373 --> 00:27:35,177 away from the light of the sun. 786 00:27:35,245 --> 00:27:36,545 For the technique to be 787 00:27:36,646 --> 00:27:38,013 accurate, it is essential 788 00:27:38,081 --> 00:27:39,815 that the sample is not exposed 789 00:27:39,883 --> 00:27:41,917 to daylight. 790 00:27:41,985 --> 00:27:43,352 >> So here we can take 791 00:27:43,453 --> 00:27:45,154 a metal tube, and we can 792 00:27:45,188 --> 00:27:47,623 hammer it into the sand outcrop, 793 00:27:47,724 --> 00:27:49,058 and in the metal tube then, 794 00:27:49,092 --> 00:27:50,693 we'll get a sample of the sand, 795 00:27:50,727 --> 00:27:52,328 and it'll stay out of sunlight, 796 00:27:52,362 --> 00:27:53,362 and then we take it back 797 00:27:53,430 --> 00:27:55,164 to a darkroom laboratory 798 00:27:55,265 --> 00:27:57,166 and remove the sand, 799 00:27:57,234 --> 00:27:58,434 still sheltered from light, 800 00:27:58,535 --> 00:27:59,535 and then we can analyze 801 00:27:59,603 --> 00:28:01,103 the optical properties of it 802 00:28:01,171 --> 00:28:02,972 to get an absolute age. 803 00:28:03,006 --> 00:28:04,273 In this case, the absolute age 804 00:28:04,374 --> 00:28:05,441 would tell us when the river 805 00:28:05,542 --> 00:28:06,642 was at this point 806 00:28:06,710 --> 00:28:08,277 in the landscape. 807 00:28:17,354 --> 00:28:19,188 >> Back at the lab, Pederson 808 00:28:19,256 --> 00:28:21,624 compares multiple sand samples, 809 00:28:21,691 --> 00:28:23,192 each from a different depth 810 00:28:23,260 --> 00:28:26,595 in the canyon deposits. 811 00:28:26,630 --> 00:28:29,231 Discovering the age of each 812 00:28:29,266 --> 00:28:31,000 individual layer of sand 813 00:28:31,067 --> 00:28:32,968 lets him estimate how rapidly 814 00:28:33,003 --> 00:28:34,436 the river has been cutting 815 00:28:34,504 --> 00:28:36,538 down through the rocks. 816 00:28:36,606 --> 00:28:37,539 >> Here at Lee's Ferry, 817 00:28:37,607 --> 00:28:38,407 we can use this last 818 00:28:38,441 --> 00:28:39,541 half-a-million-year history 819 00:28:39,643 --> 00:28:41,143 along with our absolute dates 820 00:28:41,177 --> 00:28:42,278 and all the information we get, 821 00:28:42,345 --> 00:28:45,547 and the rate of canyon-cutting 822 00:28:45,615 --> 00:28:48,050 here is about 1,000 feet 823 00:28:48,084 --> 00:28:49,818 per million years. 824 00:28:49,886 --> 00:28:51,320 >> That's one foot 825 00:28:51,354 --> 00:28:52,955 in every thousand years, 826 00:28:52,989 --> 00:28:54,723 a little more than one inch 827 00:28:54,791 --> 00:28:57,593 every century. It proves 828 00:28:57,627 --> 00:29:00,262 that the entire 5,300-foot-deep 829 00:29:00,330 --> 00:29:01,997 Grand Canyon could have 830 00:29:02,065 --> 00:29:03,766 been cut in a little more 831 00:29:03,800 --> 00:29:06,535 than 5 million years. 832 00:29:06,636 --> 00:29:08,070 In geological terms, 833 00:29:08,171 --> 00:29:11,540 the mere blink of an eye. 834 00:29:11,608 --> 00:29:13,242 The investigation is assembling 835 00:29:13,343 --> 00:29:14,977 evidence on how the Grand Canyon 836 00:29:15,078 --> 00:29:17,713 was created. 837 00:29:17,781 --> 00:29:19,815 Green clay deposits support 838 00:29:19,883 --> 00:29:21,450 the theory that an ancient lake 839 00:29:21,518 --> 00:29:23,452 was big enough to spill over and 840 00:29:23,520 --> 00:29:27,156 trigger the canyon's creation. 841 00:29:27,223 --> 00:29:28,424 Deep-water fossils prove 842 00:29:28,491 --> 00:29:29,591 that the lake existed 843 00:29:29,626 --> 00:29:31,960 6 million years ago, the right 844 00:29:31,995 --> 00:29:33,595 time to have overflowed 845 00:29:33,630 --> 00:29:36,332 and cut the Grand Canyon. 846 00:29:36,433 --> 00:29:38,033 But proving how 847 00:29:38,068 --> 00:29:39,868 the canyon-cutting began is 848 00:29:39,903 --> 00:29:42,438 only part of the investigation. 849 00:29:42,505 --> 00:29:44,073 This is one of the widest 850 00:29:44,140 --> 00:29:45,441 and deepest canyons 851 00:29:45,508 --> 00:29:47,409 in the entire world, 852 00:29:47,444 --> 00:29:48,977 and to discover how it grew 853 00:29:49,079 --> 00:29:50,813 so large, geologists will 854 00:29:50,880 --> 00:29:52,815 have to examine some of the most 855 00:29:52,882 --> 00:29:55,150 dramatic and dangerous features 856 00:29:55,218 --> 00:29:57,720 the canyon has to offer. 857 00:30:02,269 --> 00:30:03,269 >> The landscape of western 858 00:30:03,304 --> 00:30:04,637 Arizona has transformed 859 00:30:04,738 --> 00:30:05,938 from ancient mountains 860 00:30:06,006 --> 00:30:07,373 to prehistoric seas 861 00:30:07,441 --> 00:30:10,543 to a flat uplifted plain. 862 00:30:10,611 --> 00:30:13,713 Just 5.5 million years ago, 863 00:30:13,781 --> 00:30:15,181 the Grand Canyon was cut 864 00:30:15,249 --> 00:30:17,884 through this plateau. 865 00:30:17,985 --> 00:30:19,519 It happened so fast that 866 00:30:19,586 --> 00:30:21,587 geologists had to think again 867 00:30:21,622 --> 00:30:23,056 about the awesome power 868 00:30:23,157 --> 00:30:27,694 of the Colorado River. 869 00:30:27,795 --> 00:30:28,795 >> It cuts through rock not by 870 00:30:28,862 --> 00:30:30,530 yhe water wearing it away. 871 00:30:30,531 --> 00:30:31,631 You could pour water over rock 872 00:30:31,699 --> 00:30:32,899 for a long time, and nothing 873 00:30:32,966 --> 00:30:34,901 would happen. It's the tools 874 00:30:34,968 --> 00:30:36,235 that the river carries. 875 00:30:36,236 --> 00:30:37,337 The river carries boulders 876 00:30:37,404 --> 00:30:39,072 and sand, and those bump 877 00:30:39,139 --> 00:30:40,173 against each other, 878 00:30:40,240 --> 00:30:42,975 and they eat away at the rock. 879 00:30:43,043 --> 00:30:44,711 >> Every day, the Colorado 880 00:30:44,778 --> 00:30:47,714 can carry almost 500,000 tons 881 00:30:47,781 --> 00:30:49,716 of rock and debris, 882 00:30:49,783 --> 00:30:51,150 enough material to fill more 883 00:30:51,251 --> 00:30:54,620 than 100 olympic swimming pools. 884 00:30:54,688 --> 00:30:58,758 That is 5 tons every second. 885 00:30:58,792 --> 00:31:00,326 So investigating river erosion 886 00:31:00,394 --> 00:31:02,328 is never an easy task, 887 00:31:02,429 --> 00:31:03,596 because the powerful flow 888 00:31:03,697 --> 00:31:05,031 of the Colorado River 889 00:31:05,065 --> 00:31:06,599 has scoured and washed away 890 00:31:06,700 --> 00:31:08,434 many of the clues that 891 00:31:08,502 --> 00:31:11,871 the rock detectives need. 892 00:31:11,939 --> 00:31:13,306 They looked for evidence 893 00:31:13,340 --> 00:31:14,974 in the hundreds of rapids that 894 00:31:15,075 --> 00:31:18,778 disrupt the river's progress. 895 00:31:18,879 --> 00:31:20,246 The swirling rapids are created 896 00:31:20,314 --> 00:31:22,148 when flash floods sweep boulders 897 00:31:22,249 --> 00:31:23,683 into the river from the many 898 00:31:23,784 --> 00:31:26,686 smaller side canyons. 899 00:31:26,687 --> 00:31:27,754 > The river has to focus 900 00:31:27,788 --> 00:31:29,255 a lot of energy at these points 901 00:31:29,323 --> 00:31:30,957 to deal with all of the boulders 902 00:31:31,024 --> 00:31:33,025 that are coming in it. 903 00:31:33,026 --> 00:31:34,494 The more coarse boulders 904 00:31:34,528 --> 00:31:35,862 and more resistant material that 905 00:31:35,896 --> 00:31:37,330 the river has to fight against 906 00:31:37,398 --> 00:31:38,865 to accomplish its incision, 907 00:31:38,932 --> 00:31:41,067 the steeper it gets. 908 00:31:41,135 --> 00:31:41,968 >> As the water flows 909 00:31:42,069 --> 00:31:43,936 over the rapids, it cuts deep 910 00:31:43,971 --> 00:31:46,305 into the bedrock below. 911 00:31:46,340 --> 00:31:49,609 At this set of rapids alone, 912 00:31:49,710 --> 00:31:51,477 yhe river drops 10 feet, 913 00:31:51,512 --> 00:31:53,413 and there are a lot of rapids 914 00:31:53,514 --> 00:31:58,551 on this section of the Colorado. 915 00:31:58,585 --> 00:32:00,086 >> So put all these rapids 916 00:32:00,120 --> 00:32:01,354 together in a string 917 00:32:01,388 --> 00:32:02,455 through Grand Canyon, 918 00:32:02,489 --> 00:32:03,856 and that gives you the overall 919 00:32:03,924 --> 00:32:05,391 sort of unusually steep 920 00:32:05,459 --> 00:32:07,193 Grand Canyon profile 921 00:32:07,294 --> 00:32:09,295 of the river going through it. 922 00:32:09,396 --> 00:32:11,097 >> Gravity and simple physics 923 00:32:11,198 --> 00:32:12,432 are at the heart of how 924 00:32:12,533 --> 00:32:13,733 the Colorado has carved 925 00:32:13,767 --> 00:32:18,204 so much rock so quickly. 926 00:32:18,305 --> 00:32:20,206 5.5 million years ago, 927 00:32:20,274 --> 00:32:21,941 the Colorado River was flowing 928 00:32:22,009 --> 00:32:22,942 over the steep edge 929 00:32:23,010 --> 00:32:24,577 of the plateau that had been 930 00:32:24,645 --> 00:32:26,112 pushed up thousands of feet 931 00:32:26,180 --> 00:32:29,015 above sea level. 932 00:32:29,082 --> 00:32:31,551 The river ran rapidly 933 00:32:31,618 --> 00:32:33,219 over the steep downward slope 934 00:32:33,287 --> 00:32:35,621 and swept rough, rocky debris 935 00:32:35,656 --> 00:32:38,024 along in its wake. 936 00:32:38,125 --> 00:32:40,126 An incision formed, digging back 937 00:32:40,194 --> 00:32:43,763 into the edge of the plateau. 938 00:32:43,831 --> 00:32:44,931 >> The power of the river 939 00:32:45,032 --> 00:32:46,732 to incise as it dropped off 940 00:32:46,800 --> 00:32:47,934 that huge escarpment must have 941 00:32:48,001 --> 00:32:49,268 been really great. 942 00:32:49,303 --> 00:32:51,103 And so the river quickly incised 943 00:32:51,205 --> 00:32:53,005 there, and that very steep 944 00:32:53,073 --> 00:32:55,208 drop-off of incision would have 945 00:32:55,275 --> 00:32:58,010 worked its way back upstream 946 00:32:58,111 --> 00:32:59,712 through the Grand Canyon region. 947 00:32:59,746 --> 00:33:03,549 It's sort of a waterfall that, 948 00:33:03,617 --> 00:33:05,251 a few million years later, 949 00:33:05,285 --> 00:33:07,186 has spread itself out 950 00:33:07,254 --> 00:33:10,356 through the length of the river. 951 00:33:10,390 --> 00:33:11,924 >> It is this steep drop-off 952 00:33:11,992 --> 00:33:13,459 between the Colorado plateau 953 00:33:13,527 --> 00:33:15,194 and the land beneath it 954 00:33:15,262 --> 00:33:16,796 that fuels the Colorado's 955 00:33:16,830 --> 00:33:20,366 incredible erosive power. 956 00:33:20,467 --> 00:33:21,734 The river begins its life 957 00:33:21,835 --> 00:33:23,202 high in the Rocky Mountains 958 00:33:23,270 --> 00:33:25,004 in Colorado. For every mile 959 00:33:25,105 --> 00:33:27,273 that it travels, the river 960 00:33:27,341 --> 00:33:30,910 falls 10 feet. By contrast, 961 00:33:31,011 --> 00:33:33,179 the Mississippi River, a river 962 00:33:33,247 --> 00:33:35,248 moving 10 times as much water 963 00:33:35,282 --> 00:33:36,916 as the Colorado, meanders 964 00:33:37,017 --> 00:33:39,719 across a flat landscape. 965 00:33:39,820 --> 00:33:42,188 With no steep slope to drive it, 966 00:33:42,289 --> 00:33:44,023 the Mississippi can't carve 967 00:33:44,091 --> 00:33:48,361 any canyons. 968 00:33:48,428 --> 00:33:49,662 But the Grand Canyon 969 00:33:49,730 --> 00:33:51,631 is not just steep. 970 00:33:51,732 --> 00:33:54,000 It's also wide. 971 00:33:57,738 --> 00:34:00,106 And here on the south rim, 972 00:34:00,173 --> 00:34:01,374 at the heart of the National 973 00:34:01,475 --> 00:34:03,342 Park, the true majesty 974 00:34:03,377 --> 00:34:08,414 of the Grand Canyon is revealed. 975 00:34:08,482 --> 00:34:09,982 This is where the canyon 976 00:34:10,050 --> 00:34:12,218 is at its widest, as much 977 00:34:12,252 --> 00:34:17,523 as 18 miles from rim to rim. 978 00:34:17,524 --> 00:34:19,125 This landscape appears serene 979 00:34:19,192 --> 00:34:21,093 now, but its unique beauty 980 00:34:21,128 --> 00:34:25,364 was forged by violent forces. 981 00:34:25,365 --> 00:34:26,566 >> Grand Canyon, oftentimes 982 00:34:26,667 --> 00:34:27,466 we just associate it 983 00:34:27,568 --> 00:34:28,668 with the Colorado River. 984 00:34:28,735 --> 00:34:29,569 The Colorado River is what cut 985 00:34:29,636 --> 00:34:31,404 the Grand Canyon. It formed 986 00:34:31,471 --> 00:34:33,439 the initial gash to allow 987 00:34:33,540 --> 00:34:35,074 the river to flow across. 988 00:34:35,075 --> 00:34:35,975 But what makes Grand Canyon 989 00:34:36,076 --> 00:34:38,277 grand is really its width. 990 00:34:38,345 --> 00:34:39,178 And all the layers of rock 991 00:34:39,246 --> 00:34:40,413 that are exposed, and that 992 00:34:40,514 --> 00:34:43,049 isn't only solely tied 993 00:34:43,116 --> 00:34:44,050 to the Colorado River. 994 00:34:44,151 --> 00:34:45,484 What's happening is this rock 995 00:34:45,519 --> 00:34:46,519 that's exposed, it's being 996 00:34:46,587 --> 00:34:48,321 beaten on by rain, and the rain 997 00:34:48,388 --> 00:34:49,422 gets in there, and it weathers 998 00:34:49,489 --> 00:34:50,690 the rock, and it weakens it. 999 00:34:50,757 --> 00:34:51,757 And then because this is 1000 00:34:51,792 --> 00:34:52,858 so incredibly steep, gravity 1001 00:34:52,960 --> 00:34:54,427 will act on that material, 1002 00:34:54,494 --> 00:34:55,828 transporting it deeper 1003 00:34:55,862 --> 00:34:57,063 down into the river, 1004 00:34:57,130 --> 00:34:58,230 flushing it back out. 1005 00:34:58,298 --> 00:34:59,131 And that process just repeats 1006 00:34:59,199 --> 00:35:00,132 over and over again 1007 00:35:00,200 --> 00:35:01,133 to allow the canyon 1008 00:35:01,234 --> 00:35:03,035 yo get wider over time. 1009 00:35:03,136 --> 00:35:04,136 We have classic rockfalls 1010 00:35:04,204 --> 00:35:05,104 that are cascading down 1011 00:35:05,138 --> 00:35:06,305 onto the black rock 1012 00:35:06,406 --> 00:35:08,407 in the far distance. 1013 00:35:08,508 --> 00:35:09,775 Those events are indications 1014 00:35:09,876 --> 00:35:11,510 that this is actively ongoing 1015 00:35:11,578 --> 00:35:13,779 canyon-widening and retreating 1016 00:35:13,847 --> 00:35:18,017 from these processes. 1017 00:35:18,051 --> 00:35:20,119 >> The fall of these rocks 1018 00:35:20,220 --> 00:35:22,288 is not a gradual process. 1019 00:35:22,322 --> 00:35:23,756 This is erosion 1020 00:35:23,857 --> 00:35:26,826 at its most violent. 1021 00:35:26,860 --> 00:35:28,127 >> Very few people are ever 1022 00:35:28,195 --> 00:35:29,295 going to see Grand canyon 1023 00:35:29,363 --> 00:35:30,630 actually change. I've spent 1024 00:35:30,731 --> 00:35:32,231 numerous nights in Grand Canyon. 1025 00:35:32,332 --> 00:35:33,532 I've only heard one or two rocks 1026 00:35:33,567 --> 00:35:35,968 ever fall, but change will 1027 00:35:36,003 --> 00:35:37,370 happen, and when it does happen, 1028 00:35:37,437 --> 00:35:40,439 it happens very rapidly. 1029 00:35:40,474 --> 00:35:42,174 >> The rocks fall because both 1030 00:35:42,275 --> 00:35:44,010 harder and softer rocks 1031 00:35:44,111 --> 00:35:45,444 are layered, one on top of 1032 00:35:45,545 --> 00:35:48,814 the other, in the canyon walls. 1033 00:35:48,882 --> 00:35:50,549 The harder layers are made 1034 00:35:50,651 --> 00:35:53,285 of limestone and sandstone. 1035 00:35:53,353 --> 00:35:55,354 These rocks don't weather 1036 00:35:55,455 --> 00:35:58,424 easily, but the softer shale 1037 00:35:58,458 --> 00:36:00,459 beneath is made of mud that 1038 00:36:00,527 --> 00:36:02,695 expands when it rains, causing 1039 00:36:02,729 --> 00:36:06,966 the shale to crumble away. 1040 00:36:07,000 --> 00:36:08,100 >> Those weaker rocks, 1041 00:36:08,168 --> 00:36:10,102 yhey weather and retreat back, 1042 00:36:10,170 --> 00:36:11,003 and they undermine 1043 00:36:11,071 --> 00:36:12,905 the resistant cliff rocks above 1044 00:36:12,973 --> 00:36:14,607 that will then fail as dramatic 1045 00:36:14,641 --> 00:36:16,942 rockfall, landslide events, 1046 00:36:17,010 --> 00:36:17,910 allowing the canyon 1047 00:36:17,978 --> 00:36:19,912 to increase its width. 1048 00:36:29,456 --> 00:36:31,457 >> The rockfalls are merely 1049 00:36:31,525 --> 00:36:32,958 the first step towards 1050 00:36:32,993 --> 00:36:34,827 increasing the Grand Canyon's 1051 00:36:34,895 --> 00:36:38,164 enormous width. Without the help 1052 00:36:38,265 --> 00:36:39,098 of an accomplice, 1053 00:36:39,166 --> 00:36:40,599 the entire canyon would 1054 00:36:40,634 --> 00:36:42,702 fill up with debris. 1055 00:36:42,736 --> 00:36:43,703 >> Without the Colorado River, 1056 00:36:43,737 --> 00:36:44,870 you could not have the Grand 1057 00:36:44,905 --> 00:36:46,639 Canyon as wide as it is. 1058 00:36:46,707 --> 00:36:47,373 By flushing that material 1059 00:36:47,441 --> 00:36:48,441 downstream, it like... 1060 00:36:48,542 --> 00:36:49,642 it wipes it all clean 1061 00:36:49,710 --> 00:36:51,143 to allow a whole new material 1062 00:36:51,178 --> 00:36:52,344 to build up again. 1063 00:36:52,412 --> 00:36:53,179 And once you repeat that 1064 00:36:53,246 --> 00:36:54,080 over and over again, 1065 00:36:54,181 --> 00:36:55,347 it allows the canyon walls 1066 00:36:55,449 --> 00:36:57,083 to retreat back, and the entire 1067 00:36:57,184 --> 00:36:58,617 canyon just grows, as these 1068 00:36:58,719 --> 00:37:00,886 guys continue to march and push 1069 00:37:00,987 --> 00:37:02,188 and move all that material 1070 00:37:02,255 --> 00:37:04,523 downstream. 1071 00:37:04,591 --> 00:37:06,358 >> The mystery of how the Grand 1072 00:37:06,460 --> 00:37:09,095 Canyon grew so deep and so wide 1073 00:37:09,162 --> 00:37:11,530 is being solved. 1074 00:37:14,868 --> 00:37:17,002 The Colorado rapids demonstrate 1075 00:37:17,070 --> 00:37:18,003 how the steepness of the 1076 00:37:18,071 --> 00:37:19,171 riverbed helps carve 1077 00:37:19,272 --> 00:37:22,174 the canyon so quickly. 1078 00:37:22,275 --> 00:37:24,043 Rockfalls on the canyon walls 1079 00:37:24,077 --> 00:37:25,778 reveal how weaker rocks 1080 00:37:25,812 --> 00:37:27,613 rapidly widen the canyon 1081 00:37:27,714 --> 00:37:31,150 across the plains of Arizona. 1082 00:37:31,184 --> 00:37:32,885 But this is far from the end 1083 00:37:32,953 --> 00:37:36,522 of the Grand Canyon's story. 1084 00:37:36,623 --> 00:37:39,625 In just the last million years, 1085 00:37:39,693 --> 00:37:41,360 the canyon has been transformed 1086 00:37:41,428 --> 00:37:43,696 by other overwhelmingly powerful 1087 00:37:43,764 --> 00:37:45,631 natural forces. 1088 00:37:55,846 --> 00:37:58,014 >> Geologists have established 1089 00:37:58,082 --> 00:38:00,483 that over 1.7 billion years, 1090 00:38:00,551 --> 00:38:02,385 the Grand Canyon emerged 1091 00:38:02,486 --> 00:38:04,020 from ancient mountains 1092 00:38:04,121 --> 00:38:05,922 and prehistoric seas to become 1093 00:38:06,023 --> 00:38:08,024 one of North America's 1094 00:38:08,092 --> 00:38:12,028 geological icons. 1095 00:38:12,096 --> 00:38:14,731 This is a rare look at one 1096 00:38:14,798 --> 00:38:16,566 of the most remote and secret 1097 00:38:16,667 --> 00:38:19,836 parts of the Grand Canyon. 1098 00:38:19,903 --> 00:38:21,371 A series of small cone-shaped 1099 00:38:21,438 --> 00:38:22,905 mountains line the canyon's 1100 00:38:22,940 --> 00:38:25,708 edge. 1101 00:38:25,743 --> 00:38:27,644 And there are flows 1102 00:38:27,745 --> 00:38:29,646 of black rock running down 1103 00:38:29,713 --> 00:38:33,816 from each rim. 1104 00:38:33,884 --> 00:38:36,252 They come from a remarkable era 1105 00:38:36,286 --> 00:38:39,255 just 725,000 years ago, 1106 00:38:39,289 --> 00:38:41,090 when the peace of the canyon 1107 00:38:41,191 --> 00:38:42,925 was shattered... 1108 00:38:42,993 --> 00:38:46,796 [rumbling] 1109 00:38:46,830 --> 00:38:48,564 by volcanoes. 1110 00:39:02,346 --> 00:39:04,981 This is Toroweap Point, 1111 00:39:05,049 --> 00:39:06,516 in a remote area known 1112 00:39:06,617 --> 00:39:09,052 as the Arizona strip... 1113 00:39:10,621 --> 00:39:13,322 one of the most isolated places 1114 00:39:13,390 --> 00:39:15,892 in the continental U.S. 1115 00:39:17,594 --> 00:39:19,062 Few people, other than 1116 00:39:19,129 --> 00:39:21,964 geologists, ever see this area, 1117 00:39:22,032 --> 00:39:23,332 although it boasts some of the 1118 00:39:23,434 --> 00:39:27,704 canyon's most stunning views. 1119 00:39:27,805 --> 00:39:29,939 The rock detectives come to see 1120 00:39:29,973 --> 00:39:31,874 how explosive volcanic 1121 00:39:31,975 --> 00:39:33,309 eruptions have changed 1122 00:39:33,343 --> 00:39:35,311 the canyon in the comparatively 1123 00:39:35,345 --> 00:39:39,315 recent geological past. 1124 00:39:39,416 --> 00:39:41,050 This black rock that seems 1125 00:39:41,151 --> 00:39:42,885 to have spilled over the rim 1126 00:39:42,953 --> 00:39:44,687 of the canyon is an ancient 1127 00:39:44,755 --> 00:39:47,056 lava flow, what was once 1128 00:39:47,157 --> 00:39:49,859 boiling-hot rock, 1129 00:39:49,893 --> 00:39:54,964 Forever frozen in time. 1130 00:39:54,965 --> 00:39:56,232 >> Powell talked about a river 1131 00:39:56,300 --> 00:39:57,867 of molten magma pouring down 1132 00:39:57,935 --> 00:40:01,604 into a river of melted snow. 1133 00:40:01,605 --> 00:40:02,605 And he talked about 1134 00:40:02,706 --> 00:40:04,307 how dramatic it must have been, 1135 00:40:04,374 --> 00:40:05,541 the boiling and seething 1136 00:40:05,576 --> 00:40:07,210 and the steam, and... 1137 00:40:07,277 --> 00:40:09,579 it must have been amazing. 1138 00:40:09,646 --> 00:40:13,449 You would picture red-hot lava 1139 00:40:13,484 --> 00:40:14,917 like you would see in Hawaii 1140 00:40:15,018 --> 00:40:16,652 pouring down the canyon walls 1141 00:40:16,754 --> 00:40:18,287 and coating them, and then 1142 00:40:18,355 --> 00:40:19,922 once it reached the river, 1143 00:40:19,990 --> 00:40:21,557 it would... you know, it would 1144 00:40:21,658 --> 00:40:24,560 immediately create just giant 1145 00:40:24,628 --> 00:40:26,295 clouds of steam. 1146 00:40:29,099 --> 00:40:30,733 >> The extensive lava flows 1147 00:40:30,834 --> 00:40:33,002 erupting from as many as 100 1148 00:40:33,103 --> 00:40:34,937 cinder-cone volcanoes 1149 00:40:35,005 --> 00:40:36,105 had a dramatic effect 1150 00:40:36,206 --> 00:40:37,473 on the Colorado River 1151 00:40:37,574 --> 00:40:39,575 running below. 1152 00:40:39,643 --> 00:40:41,444 Crow believes that on at least 1153 00:40:41,478 --> 00:40:43,279 8 occasions, the volcanic 1154 00:40:43,347 --> 00:40:45,014 eruptions created huge 1155 00:40:45,115 --> 00:40:46,916 lava dams that blocked 1156 00:40:46,984 --> 00:40:50,286 the river completely. 1157 00:40:50,354 --> 00:40:51,487 >> Well, behind me here 1158 00:40:51,555 --> 00:40:54,524 is one of many basalt remnants. 1159 00:40:54,558 --> 00:40:56,292 They're the remains of lava 1160 00:40:56,393 --> 00:40:57,460 flows that poured down the 1161 00:40:57,528 --> 00:40:59,562 canyon, partially filling it. 1162 00:40:59,663 --> 00:41:00,997 And then subsequently, 1163 00:41:01,031 --> 00:41:04,934 the Colorado River has removed 1164 00:41:05,002 --> 00:41:08,371 all but a few little chunks. 1165 00:41:08,438 --> 00:41:10,339 >> The lava dams brought 1166 00:41:10,374 --> 00:41:12,909 even the powerful Colorado River 1167 00:41:12,976 --> 00:41:15,178 to a halt... 1168 00:41:15,279 --> 00:41:20,483 For a while. 1169 00:41:20,551 --> 00:41:22,652 In time, the dams were no match 1170 00:41:22,753 --> 00:41:24,287 for the Colorado. 1171 00:41:24,388 --> 00:41:25,254 The rising pressure 1172 00:41:25,289 --> 00:41:26,722 of the dammed river behind them 1173 00:41:26,790 --> 00:41:29,091 eventually became too much, 1174 00:41:29,159 --> 00:41:31,260 and they shattered. 1175 00:41:37,000 --> 00:41:39,368 This explosive episode 1176 00:41:39,436 --> 00:41:40,536 has left its mark 1177 00:41:40,637 --> 00:41:43,840 on the canyon's walls. 1178 00:41:43,907 --> 00:41:45,107 Today, the cones appear 1179 00:41:45,175 --> 00:41:48,110 to be extinct and lifeless, 1180 00:41:48,178 --> 00:41:49,645 although some geologists believe 1181 00:41:49,713 --> 00:41:51,280 that the volcanoes might not 1182 00:41:51,348 --> 00:41:54,550 be finished quite yet. 1183 00:41:54,618 --> 00:41:57,186 >> The last eruption that sent 1184 00:41:57,254 --> 00:41:58,454 lava pouring into Grand Canyon 1185 00:41:58,555 --> 00:42:00,022 probably occurred about 1186 00:42:00,090 --> 00:42:02,091 100,000 years ago. There is 1187 00:42:02,192 --> 00:42:03,926 evidence for an eruption 1188 00:42:03,994 --> 00:42:06,996 on the rim that didn't actually 1189 00:42:07,064 --> 00:42:08,631 make it into Grand Canyon 1190 00:42:08,699 --> 00:42:10,366 that's 1,000 years old. 1191 00:42:10,434 --> 00:42:12,835 So there's... there's, you know, 1192 00:42:12,903 --> 00:42:14,070 I think, a good chance 1193 00:42:14,104 --> 00:42:16,472 that in the future, there may 1194 00:42:16,540 --> 00:42:19,008 be eruptions here as well. 1195 00:42:19,109 --> 00:42:21,544 >> The Grand Canyon's future 1196 00:42:21,645 --> 00:42:23,646 has yet to be written, 1197 00:42:23,714 --> 00:42:25,514 but investigators now understand 1198 00:42:25,549 --> 00:42:29,352 the story of its past. 1199 00:42:29,419 --> 00:42:30,920 The calcium in the garnet 1200 00:42:30,988 --> 00:42:31,787 discovered at the base 1201 00:42:31,822 --> 00:42:32,822 of the canyon reveals 1202 00:42:32,923 --> 00:42:34,457 the ancient beginnings 1203 00:42:34,524 --> 00:42:35,992 of this landscape-- 1204 00:42:36,059 --> 00:42:39,362 an immense mountain range. 1205 00:42:39,463 --> 00:42:41,330 Limestone rocks show 1206 00:42:41,365 --> 00:42:43,165 that the canyon was only formed 1207 00:42:43,267 --> 00:42:47,436 5.5 million years ago. 1208 00:42:47,537 --> 00:42:49,171 Green clays that can only form 1209 00:42:49,273 --> 00:42:50,806 in deep water prove that 1210 00:42:50,874 --> 00:42:52,275 a huge lake, bigger than 1211 00:42:52,376 --> 00:42:53,609 Lake Michigan, could have been 1212 00:42:53,644 --> 00:42:54,644 the trigger for this 1213 00:42:54,711 --> 00:42:57,413 canyon-carving. 1214 00:42:57,447 --> 00:42:58,981 And rockfalls from 1215 00:42:59,082 --> 00:43:00,416 the crumbling cliff faces 1216 00:43:00,450 --> 00:43:02,084 of the canyon rim are evidence 1217 00:43:02,185 --> 00:43:03,519 of how the canyon grew 1218 00:43:03,553 --> 00:43:07,356 to the shape it is today. 1219 00:43:07,424 --> 00:43:09,525 Geologists have been studying 1220 00:43:09,626 --> 00:43:13,262 the canyon since the mid-1800's. 1221 00:43:13,330 --> 00:43:14,630 Yet even after more than 1222 00:43:14,731 --> 00:43:16,799 a century of investigation, 1223 00:43:16,900 --> 00:43:18,534 the story is still 1224 00:43:18,635 --> 00:43:21,003 far from finished. 1225 00:43:21,071 --> 00:43:22,705 >> The landscape is evolving, 1226 00:43:22,773 --> 00:43:23,973 and it's going to be changing 1227 00:43:24,007 --> 00:43:25,608 through the geological future. 1228 00:43:25,642 --> 00:43:27,710 And so the story about 1229 00:43:27,778 --> 00:43:28,978 the geology and the fascinating 1230 00:43:29,079 --> 00:43:30,246 questions here is not one 1231 00:43:30,280 --> 00:43:31,547 that's over, and it's going to 1232 00:43:31,615 --> 00:43:33,149 continue to evolve as scientists 1233 00:43:33,183 --> 00:43:37,086 continue to do work here. 1234 00:43:37,187 --> 00:43:39,055 >> The dynamic geological 1235 00:43:39,089 --> 00:43:41,157 phenomenon of the Grand Canyon 1236 00:43:41,258 --> 00:43:42,892 is a place where the vast 1237 00:43:42,960 --> 00:43:44,727 fiery forces within the Earth's 1238 00:43:44,795 --> 00:43:46,629 crust do battle with 1239 00:43:46,730 --> 00:43:49,265 the inexorable power of water. 1240 00:43:49,366 --> 00:43:51,434 The result--a natural wonder 1241 00:43:51,535 --> 00:43:52,769 whose walls record 1242 00:43:52,770 --> 00:43:54,970 nearly 2 billion years 1243 00:43:54,971 --> 00:43:56,571 of our planet's turblent 1244 00:43:56,572 --> 00:43:58,572 geological history. 1245 00:43:58,573 --> 00:44:03,573 -- Sync, corrected by elderman -- -- for www.MY-SUBS.com --