They've
also determined that the Himalayan Mountains are still growing higher,
at a rate of about 2.4 in/6.1cm per year. That's twice as fast as
previously thought. A growth rate of 2.4 in/6.1cm per year doesn't
sound like very much. If you think about it, that means in the last
26,000 years the Himalayans have risen almost a mile into the upper
reaches of the earth's atmosphere!
When
Hillary and Norgay
climbed to the top of Everest they wore oxygen tanks. Because Everest
is so high it juts into the upper reaches of the earth's atmosphere,
where there are much lower concentrations of oxygen than at sea
level. What that means to folks trekking up the side of Everest
is that their bodies get less oxygen from each breath they breathe
while climbing. But their brains and muscles require the same amount
of oxygen to perform as they would at sea level. That makes it especially
tough to climb Everest.
Try
to imagine what it feels like to climb up a mountain with very little
oxygen in your body - you get dizzy, your nose, fingers and feet
get numb and tingly, your heart thunders in your chest trying furiously
to keep up with the muscles' demand for oxygen. You feel sleepy,
confused, downright stupid as your brain struggles to function on
limited oxygen. Every step you take is extremely slow and plodding,
requiring every ounce of will you have. Hillary and Norgay had extra
oxygen to help them make the trip, but there have been a few people
who have made the trip since who did it without the aid of oxygen
- taking one step about every five minutes! Approximately
6,000 climbers have attempted the summit of Everest, but only 2,249
have made it. Over 200 people have died trying and of those, at
least 120 bodies are still missing on the mountain.
Highest Mountains
Mount
Everest is just one of over 30 peaks in the Himalayas that are over
24,000 ft/7315m high. Himalaya is a Sanskrit word meaning, "abode
of snow", which is so true. The name of the mountain in Nepal
is Sagarmatha, which means "goddess of the sky". The snowfields
which dominate many of the peaks in the Himalayas are permanent.
Yes, they never melt (not even in the summer). That means
there are glaciers in the Himalayas - lots of them. Mount Everest
is permanently covered in a layer of ice, topped with snow. The
"top" of the mountain at which the elevation was measured can vary
as much as twenty feet or more, depending on how much snow has fallen
on its peak. Scientists believe that the actual tip of the rock
lies tens of feet below the ice and snow on its summit. There are
current plans to use ground penetrating radar to get a reading of
the actual height of the mountain beneath all that snow.
Although the Himalayan Range is only 1,550 miles/2480km long, the
average height of all the major peaks in the Himalayas easily makes
it the highest mountain range on land.
The Birth of a Mountain
Mountains
aren't just big piles of dirt, they're made of solid rock. Believe
it or not, the rocks that make up the Himalayan mountains used to
be an ancient sea floor. Over millions of years, rivers washed rocks
and soil from existing mountains on the Indian subcontinent and
nearby Asia into a shallow sea where the sediment
was deposited on the floor. Layer upon layer of sediment built up
over millions of years until the pressure and weight of the overlying
sediment caused the stuff way down deep to turn into rock. Then
about 40 million years ago, in a process called "uplifting", the
sea floor began to be forced upward forming mountains.
Plate Tectonics
in Action
What
caused the sea floor to be pushed up toward the sky was the result
of the action of plate tectonics.
The theory of plate tectonics was developed about thirty years ago
by scientists who discovered that the
earth's crust is made up of many
"plates" which are constantly moving around. They are still
moving around, even today, but the speeds at which they move are
REALLY SLOW. In human terms the movement can't even be seen, but
it can be felt occasionally when we have earthquakes. Earthquakes
happen when plate margins
(edges) move past, or bump into each other. In the case of the Himalayan
mountains, the continent of India is part of a plate that "crashed"
into southwest Asia, but it didn't stop when it hit. It continued
to push northward, crushing and rumpling the earth's crust, resulting
in the mountains we see today. If you look at a map of the Himalayas,
you can see that the mountains look kind of like a rumpled blanket.
India is still pushing northward today, raising the Himalayas even
higher!
The Himalayan Mountains are forming where two tectonic
plates are crashing into each other, known as a convergent
boundary. |
Need
more earth science information? Read about the geologic
history of earth.
How Do They Know?
Scientists
know this because they've been measuring the increasing height of
the mountains. There have also been a lot of earthquakes recorded
down deep in the mountains, which indicates continuing movement.
The Himalayas are growing, but only about 2 inches a year. That's
not very much in human terms, but imagine how much that would be
over millions of years! You may be thinking, "That would
have been kinda cool to be here on earth 40 million years ago to
be able to watch the Himalayas forming". You would have been really
bored, though. The movement that took many millions of years to
form the mountain range is still taking place today, and I doubt
you would stake out a camp at the foot of the mountains just to
watch them grow. You'd be waiting a LONG TIME.
