Why is Mount Everest so tall? - Michele Koppes
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0:07 - 0:08Every spring,
-
0:08 - 0:12hundreds of adventure-seekers dream
of climbing Qomolangma, -
0:12 - 0:15also known as Mount Everest.
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0:15 - 0:17At base camp, they hunker down for months
-
0:17 - 0:22waiting for the chance to scale
the mountain's lofty, lethal peak. -
0:22 - 0:26But why do people risk life and limb
to climb Everest? -
0:26 - 0:28Is it the challenge?
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0:28 - 0:29The view?
-
0:29 - 0:32The chance to touch the sky?
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0:32 - 0:38For many, the draw is Everest's status
as the highest mountain on Earth. -
0:38 - 0:40There's an important distinction
to make here. -
0:40 - 0:45Mauna Kea is actually the tallest
from base to summit, -
0:45 - 0:48but at 8850 meters above sea level,
-
0:48 - 0:51Everest has the highest altitude
on the planet. -
0:51 - 0:54To understand how
this towering formation was born, -
0:54 - 0:58we have to peer deep
into our planet's crust, -
0:58 - 1:00where continental plates collide.
-
1:00 - 1:03The Earth's surface
is like an armadillo's armor. -
1:03 - 1:06Pieces of crust constantly move over,
-
1:06 - 1:07under,
-
1:07 - 1:09and around each other.
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1:09 - 1:14For such huge continental plates,
the motion is relatively quick. -
1:14 - 1:17They move two to four
centimeters per year, -
1:17 - 1:19about as fast as fingernails grow.
-
1:19 - 1:21When two plates collide,
-
1:21 - 1:25one pushes into or underneath the other,
buckling at the margins, -
1:25 - 1:30and causing what's known as uplift
to accomodate the extra crust. -
1:30 - 1:32That's how Everest came about.
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1:32 - 1:3750 million years ago, the Earth's
Indian Plate drifted north, -
1:37 - 1:39bumped into the bigger Eurasian Plate,
-
1:39 - 1:43and the crust crumpled,
creating huge uplift. -
1:43 - 1:46Mountain Everest lies at the heart
of this action, -
1:46 - 1:49on the edge of the Indian-Eurasian
collision zone. -
1:49 - 1:53But mountains are shaped by forces
other than uplift. -
1:53 - 1:58As the land is pushed up,
air masses are forced to rise as well. -
1:58 - 2:03Rising air cools, causing any water
vapor within it to condense -
2:03 - 2:05and form rain or snow.
-
2:05 - 2:08As that falls,
it wears down the landscape, -
2:08 - 2:13dissolving rocks or breaking them down
in a process known as weathering. -
2:13 - 2:15Water moving downhill carries
the weathered material -
2:15 - 2:17and erodes the landscape,
-
2:17 - 2:21carving out deep valleys and jagged peaks.
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2:21 - 2:26This balance between uplift and erosion
gives a mountain its shape. -
2:26 - 2:28But compare the celestial peaks
of the Himalayas -
2:28 - 2:30to the comforting hills of Appalachia.
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2:30 - 2:33Clearly, all mountains are not alike.
-
2:33 - 2:36That's because time
comes into the equation, too. -
2:36 - 2:40When continental plates first collide,
uplift happens fast. -
2:40 - 2:43The peaks grow tall with steep slopes.
-
2:43 - 2:47Over time, however, gravity and water
wear them down. -
2:47 - 2:49Eventually, erosion overtakes uplift,
-
2:49 - 2:53wearing down peaks
faster than they're pushed up. -
2:53 - 2:56A third factor shapes mountains: climate.
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2:56 - 3:01In subzero temperatures, some snowfall
doesn't completely melt away, -
3:01 - 3:04instead slowly compacting
until it becomes ice. -
3:04 - 3:09That forms the snowline, which occurs
at different heights around the planet -
3:09 - 3:11depending on climate.
-
3:11 - 3:15At the freezing poles,
the snowline is at sea level. -
3:15 - 3:19Near the equator, you have to climb
five kilometers before it gets cold enough -
3:19 - 3:21for ice to form.
-
3:21 - 3:25Gathered ice starts flowing under
its own immense weight -
3:25 - 3:29forming a slow-moving frozen river
known as a glacier, -
3:29 - 3:31which grinds the rocks below.
-
3:31 - 3:34The steeper the mountains,
the faster ice flows, -
3:34 - 3:37and the quicker it carves
the underlying rock. -
3:37 - 3:41Glaciers can erode landscapes
swifter than rain and rivers. -
3:41 - 3:45Where glaciers cling to mountain peaks,
they sand them down so fast, -
3:45 - 3:50they lop the tops off
like giant snowy buzzsaws. -
3:50 - 3:54So then, how did the icy Mount Everest
come to be so tall? -
3:54 - 3:58The cataclysmic continental clash
from which it arose -
3:58 - 4:01made it huge to begin with.
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4:01 - 4:03Secondly, the mountain lies
near the tropics, -
4:03 - 4:08so the snowline is high,
and the glaciers relatively small, -
4:08 - 4:10barely big enough to widdle it down.
-
4:10 - 4:13The mountain exists in a perfect storm
of conditions -
4:13 - 4:16that maintain its impressive stature.
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4:16 - 4:18But that won't always be the case.
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4:18 - 4:20We live in a changing world
where the continental plates, -
4:20 - 4:22Earth's climate,
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4:22 - 4:24and the planet's erosive power
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4:24 - 4:28might one day conspire to cut
Mount Everest down to size. -
4:28 - 4:32For now, at least, it remains legendary
in the minds of hikers, -
4:32 - 4:33adventurers,
-
4:33 - 4:35and dreamers alike.
- Title:
- Why is Mount Everest so tall? - Michele Koppes
- Description:
-
View full lesson: http://ed.ted.com/lessons/why-is-mount-everest-so-tall-michele-koppes
At 8,850 meters above sea level, Qomolangma, also known as Mount Everest, has the highest altitude on the planet. But how did this towering formation get so tall? Michele Koppes peers deep into our planet’s crust, where continental plates collide, to find the answer.
Lesson by Michele Koppes, animation by Provincia Studio.
- Video Language:
- English
- Team:
- closed TED
- Project:
- TED-Ed
- Duration:
- 04:53
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