How North America got its shape - Peter J. Haproff
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0:11 - 0:15The geography of our planet is in flux.
-
0:15 - 0:20Each continent has ricocheted around
the globe on one or more tectonic plates, -
0:20 - 0:23changing quite dramatically with time.
-
0:23 - 0:25Today, we'll focus on North America
-
0:25 - 0:27and how its familiar landscape
and features -
0:27 - 0:31emerged over hundreds
of millions of years. -
0:31 - 0:35Our story begins about
750 million years ago. -
0:35 - 0:38As the super continent Rodinia
becomes unstable, -
0:38 - 0:42it rifts along what's now the west coast
of North America -
0:42 - 0:45to create the Panthalassa Ocean.
-
0:45 - 0:48You're seeing an ancestral continent
called Laurentia, -
0:48 - 0:51which grows over the next few hundred
million years -
0:51 - 0:56as island chains collide with it
and add land mass. -
0:56 - 0:59We're now at 400 million years ago.
-
0:59 - 1:03Off today's east coast, the massive
African plate inches westward, -
1:03 - 1:06closing the ancient Iapetus Ocean.
-
1:06 - 1:10It finally collides with Laurentia
at 250 million years -
1:10 - 1:14to form another supercontinent Pangea.
-
1:14 - 1:16The immense pressure causes
faulting and folding, -
1:16 - 1:20stacking up rock to form
the Appalachian Mountains. -
1:20 - 1:22Let's fast forward a bit.
-
1:22 - 1:26About 100 million years later,
Pangea breaks apart, -
1:26 - 1:28opening the Southern Atlantic Ocean
-
1:28 - 1:32between the new North American Plate
and the African Plate. -
1:32 - 1:33We forge ahead,
-
1:33 - 1:36and now the eastward-moving
Farallon Plate -
1:36 - 1:39converges with the present-day west coast.
-
1:39 - 1:43The Farallon Plate's greater density
makes it sink beneath North America. -
1:43 - 1:45This is called subduction,
-
1:45 - 1:48and it diffuses water into
the magma-filled mantle. -
1:48 - 1:51That lowers the magma's melting point
-
1:51 - 1:54and makes it rise into the overlying
North American plate. -
1:54 - 1:58From a subterranean chamber,
the magma travels upwards -
1:58 - 2:01and erupts along a chain of volcanos.
-
2:01 - 2:04Magma still deep underground slowly cools,
-
2:04 - 2:07crystallizing to form solid rock,
-
2:07 - 2:11including the granite now found
in Yosemite National Park -
2:11 - 2:13and the Sierra Nevada Mountains.
-
2:13 - 2:15We'll come back to that later.
-
2:15 - 2:17Now, it's 85 million years ago.
-
2:17 - 2:20The Farallon Plate becomes less steep,
-
2:20 - 2:24causing volcanism to stretch eastward
and eventually cease. -
2:24 - 2:26As the Farallon Plate subducts,
-
2:26 - 2:28it compresses North America,
-
2:28 - 2:31thrusting up mountain ranges
like the Rockies, -
2:31 - 2:34which extend over 3,000 miles.
-
2:34 - 2:38Soon after, the Eurasian Plate rifts
from North America, -
2:38 - 2:40opening the North Atlantic Ocean.
-
2:40 - 2:42We'll fast forward again.
-
2:42 - 2:45The Colorado Plateau now uplifts,
-
2:45 - 2:48likely due to a combination
of upward mantle flow -
2:48 - 2:51and a thickened North American Plate.
-
2:51 - 2:55In future millennia, the Colorado River
will eventually sculpt the plateau -
2:55 - 2:57into the epic Grand Canyon.
-
2:57 - 3:0330 million years ago, the majority of
the Farallon Plate sinks into the mantle, -
3:03 - 3:07leaving behind only small corners
still subducting. -
3:07 - 3:10The Pacific
and North American plates converge -
3:10 - 3:14and a new boundary
called the San Andreas Fault forms. -
3:14 - 3:17Here, North America moves to the south,
-
3:17 - 3:20sliding against the Pacific Plate,
which shifts to the north. -
3:20 - 3:23This plate boundary still exists today,
-
3:23 - 3:26and moves about 30 millimeters per year
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3:26 - 3:29capable of causing
devastating earthquakes. -
3:29 - 3:32The San Andreas also pulls apart
western North America -
3:32 - 3:35across a wide rift zone.
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3:35 - 3:39This extensional region is called
the Basin and Range Province, -
3:39 - 3:41and through uplift and erosion,
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3:41 - 3:46is responsible for exposing the once deep
granite of Yosemite and the Sierra Nevada. -
3:46 - 3:49Another 15 million years off the clock,
-
3:49 - 3:54and magma from the mantle burns
a giant hole into western North America, -
3:54 - 3:57periodically erupting onto the surface.
-
3:57 - 4:01Today, this hotspot feeds
an active supervolcano -
4:01 - 4:03beneath Yellowstone National Park.
-
4:03 - 4:08It hasn't erupted
in the last 174,000 years, -
4:08 - 4:09but if it did,
-
4:09 - 4:13its sheer force could blanket
most of the continent with ash -
4:13 - 4:16that would blacken the skies
and threaten humanity. -
4:16 - 4:19The Yellowstone supervolcano
is just one reminder -
4:19 - 4:23that the Earth continues
to seethe below our feet. -
4:23 - 4:26Its mobile plates put the planet
in a state of constant flux. -
4:26 - 4:29In another few hundred million years,
-
4:29 - 4:33who knows how the landscape
of North America will have changed. -
4:33 - 4:36As the continent slowly morphs
into something unfamiliar, -
4:36 - 4:39only geological time will tell.
- Title:
- How North America got its shape - Peter J. Haproff
- Description:
-
View full lesson: http://ed.ted.com/lessons/how-north-america-got-its-shape-peter-j-haproff
North America didn’t always have its familiar shape, nor its famed mountains, canyons, and plains: all of that was once contained in an unrecognizable mass, buried deep in Rodinia, a huge supercontinent that lay on the face of the Earth. Peter J. Haproff explains how it took millions of years and some incredible plate tectonics to forge the continent we know today.
Lesson by Peter J. Haproff, animation by Globizco.
- Video Language:
- English
- Team:
- closed TED
- Project:
- TED-Ed
- Duration:
- 04:58
Jessica Ruby approved English subtitles for How North America got its shape - Peter J. Haproff | ||
Jessica Ruby accepted English subtitles for How North America got its shape - Peter J. Haproff | ||
Jessica Ruby edited English subtitles for How North America got its shape - Peter J. Haproff | ||
Jennifer Cody edited English subtitles for How North America got its shape - Peter J. Haproff |