Tibetan Plateau (Asia): Mountain Ranges
1. Zoom from the Grand Canyon to the Tibetan Plateau
2. When viewed from space, it is likely that there is no more impressive
geologic wonder than the Tibetan Plateau.
a. 2.5 million sq. km of land approximately 5 km above sea level
b. Called the “roof of the world”
c. Contains the world’s highest mountain range: Himalayas
d. Contains the world’s highest mountain: Everest, 29,029 ft; 8848 m
3. Now, there is actually a lot of ways to define biggest and tallest.
a. As a mountain range, Andes longest (>7000 km) (Himalayas only
2400 km)
b. As a single mountain on land, McKinley (Denali) rises farther from the
surrounding valley (~18,400 ft) than any other mt on land (only
12,000 ft -15,000 ft for Everest).
c. And as a single mountain, nothing compares to Mauna Kea (Hawaii),
which rises more than 33,000 feet off of the sea floor (though most of
the mountain is under water)
d. And remember from the second lecture: the peak of Chimborazo in
Ecuador, because it is at the equator, is the highest point measured
from the center of the earth.
e. But, it is impossible to compare with the Tibetan Plateau in terms of
the numbers of tall mountains. There are about 450 mountains in the
world that are higher than 7000 m above sea level. All of them are on
the Tibetan Plateau. The highest mountain outside of the TP is
Aconcagua, in the Andes in South America, and it is 6962 m high.
4. The Tibetan Plateau does not contain a single mountain range, but many
a. Explain the idea of a mountain range.
b. Most impressive is the Himalayan Mountain Range, which is at the
southern end of the TP, and separates it from the Indian subcontinent.
c. Other ranges include the Kunlun range on the north; Qilian range in
the northeast (bordering Gobi Desert); on east by Hengduan Mtns in
Sichuan; in the west, the Karakoram range (Pakistan)
d. Take a tour of the major mountains
5. TP contains an enormous amount of water
a. The Himalayas alone have 15,000 glaciers containing 12,000 km3 of
ice
b. In fact, rivers that feed 3 billion people (almost half the world!) get
their starts in the TP – Ganges, Brahmaputra, Indus, Mekong, Yellow,
Yangtze – from glacial runoff.
c. TP acts as a barrier to monsoon air patterns
i. Explain how mountains cause rain/snow
ii. This is why vast snowfall on southern Himalayas, but little on
top of the plateau
iii. Also explains the Gobi desert
iv. Also prevents cold Arctic winter winds from reaching India.
d. There are some spectacular lakes on the plateau ..
e. But some places on the plateau can be very dry. In the Changthang
region of plateau (NW), temps drop to -40F in winter, and it is very
dry – lowest population density anywhere in the world that isn’t
Antarctica or Greenland.
6. It is a theme of this course, repeated over and over, that the powerful forces
of erosion are constantly ripping down the land and washing it to the sea.
And mountains get eroded faster than anything else. (Appalachians were
once the Himalayas of their day, but after 100s millions of years, not much
left) So, how is it that the Himalayas are so tall?
a. They are young! In fact they are still going up.
b. Best current example of a continent/continent collision
c. Explain India-Asia collision, including underthrusting
d. Explain plate tectonic history (Gondwana, India&Madagascar go
south, India breaks away and goes north (85 Ma), Tethys closes up
(65 Ma), and collision continues today at about 4 cm/yr
e. Everything in between is smashed together
i. ocean sedimentary rocks (limestones) are at the top of Everest!
ii. The roof of the world is made of rocks from the bottom of the
sea floor!
f. Some parts are still rising fast (Nanga Parbat – rising 1 cm/yr); others
eroding fast
g. Here an even stranger thing – some parts are rising faster than
eroding BECAUSE they are eroding fast!
i. Explain isostasy of mountains – Demo with tempurpedic foam?
ii. As you remove rock, the crust rises up. So if you remove MOST
of the rock, but leave a few peaks, they will rise up [we will
come back to this in lecture on Yosemite]
7. You can visit many of these regions. You can do it the hard way or the easy
way.
a. Easy way: Fly in to Kathmandu (capitol of Nepal) and take trips out
from there.
i. Fascinating city, with ancient history, sacred to Hinduism and
Buddhism
ii. In the valley between mountain ranges (less than a mile high,
lower than Denver), so temperatures are mild and air is easy to
breathe.
b. Hard way: you can climb them. These involve long treks, traveling
from one base camp to the next.
i. Need to be in top physical shape, not only because of the ascent
and low temps (frostbite common), but because of the thin air.
By the time you get to an elevation of about 5.5 km above sea
level, there is half as much air as there is at sea level. At the top
of Everest, air pressure is down to a third. A person who would
normally breathe 20-30 times a minute would have to breathe
80-90 times a minute, and many climbers have become
exhausted just from the act of breathing so heavily.
ii. As a result, bottled oxygen became standard for use in climbing
the tallest peaks following its first use in 1922.
iii. When Edmund Hillary and Tenzing Norgay first climbed to the
summit of Everest in 1953, they used oxygen.
iv. However, some of the top climbers today now try the ascents
without oxygen.
1. In 1978, Reinhold Messner first topped Everest without
oxygen. Two years later he did it again, solo, in 3 days
from the base camp at 21,000 feet.
2. The oxygen lets up a lot of people who might not be in
top physical shape, and many of these have died. On one
day in 1996 there were 34 people climbing Everest; 8
died.
3. But as of 2008, Everest had been climbed about 4100
times by 2700 different people (sherpas may do it many
times – one, Apa Sherpa, has done it 21 times). And
there have been over 220 deaths. Because it is often
impossible to get the bodies down, the path is lined with
the frozen bodies.
c. It is, in any case, a great challenge to reach the mountains, but
incredibly rewarding. But the difficulty in reaching them caused it to
take almost 50 years to determine that Everest was, indeed, the
highest mountain.
i. Work began in 1808 by the British’s Great Trigonometric
Survey of India (explain triangulation).
ii. But Everest wasn’t identified until 1852. Andrew Waugh, in
charge of the British Survey, redid the calculations and
announced Everest’s height in 1856. The calculation came out
to exactly 29000 feet, but they didn’t want people to think they
had rounded, so they arbitrarily made it 29002 ft. There have
multiple surveys made, but by surveying equipment and by
satellite, and though the most common height is 29,029, there
is still uncertainty, and numbers vary from 29017 to 29035.
iii. The Tibetan name for Everest is Jomolumgma, meaning “Holy
Mother,” but Andrew Waugh named it after Colonel Sir George
Everest, who was Waugh’s predecessor as chief of the Indian
survey.
8. The Tibetan Plateau and collision of India into Asia have two broader
influences.
a. The collision causes tectonic disruption throughout Asia. Most
earthquake deaths in the world are related to this plate collision
i. 2004 Sumatra – 225,000 dead
ii. 2005 Pakistan – 75,000 dead
iii. 2008 Sichuan – 70,000 dead
b. Role in cooling the planet for the past 60 Ma
i. Mountains erode fast; carbonic acid in rain reacts with the
rock; become marine animal shells; locked away as limestone;
mountains are lick sponges, soaking up CO2 from atmosphere;
1. Before Himalayas, CO2 levels were 4-8 times what they
are now
2. Whole world has been gradually cooling over the past
65 million years, during the time of the rise of the
Himalayas.
9. Top 5:
a. Andes (South America) – Altiplano is vast, both tectonic and volcanic.
[Will talk about more in Lecture 30], and is the longest mountain
chain (7000 km)
b. Alps (Europe)
c. Rockies (N Amer)
d. Mt. McKinley – as the single largest mountain – dwarfs Everest in
comparison
Questions:
1. Some rivers cut right across the Himalayan range. How
do you think they might have formed?
2. Which do you think should be called the “world’s tallest
mountain?” Everest, McKinley, Chimborazo, or Mauna
Kea.