The Himalayan Mountains span the countries of Pakistan,
India, Nepal, and Tibet
The Indian plate is converging with the Eurasian plate,
creating the Himalayas
The path traveled by the Indian plate over the last
100 million years
Side-view of the Indian-Eurasian collision, producing
Side-view of continent-continent convergence
Orogeny of the Himalayan Mountains
The Himalayan Mountains are some of the most beautiful
features of nature and are today home to many different groups of people.
The mountains span the countries of India, Nepal, Pakistan, and Tibet
in South Asia and are the location of the tallest mountains in the world.
The Himalayan Mountains, however, have not always been the natural wonder
that they are today. 100 Million years ago, in fact, the whole Indian
sub-continent, sans Himalayas, was its own island.
Farming the slopes of the Himalayas, Nepal
How the Himalayas
The present-day continental formations on the world are, geologically
speaking, relatively recent formations. 250 Million years ago, the continents
were part of one giant super-continent, called Pangea. Due to plate
tectonics, the crustal plates of the earth moving independently, pushing
and pulling into one another and creating constant geologic activity,
the continent of Pangea was ripped apart. The new continents slowly
spread around the world creating the continents and oceans that we know
today. As a part of this ripping apart, the Indian plate broke off from
the bottom of Pangea and began to move northward, toward the larger
Eurasian plate. India charged across the ocean at a rate of 10 –
15 cm/ year, an unusually fast rate for crustal plates. Over the next
several million years, the movement of the Indian plate slowly closed
the Tethys ocean that had separated India from Eurasia.
Approximately 55 million years ago, the Indian plate was heading steadily
for the Eurasian plate, and approximatley ten million years ago crashed
into it (see diagrams at right). The oceanic crust portion of the plate
broke off, and, due to a greater density, was subducted underneath Eurasia
and incorporated back into the mantle. The continental crust portion
of the plate, however, is less dense. Therefore, it would not easily
subduct beneath the greater plate. As a result, the two continents continued
crashing into each other, with neither able to sink below the other.
This collision is what created the Himalayan Mountain belt. The continental
crust here is buckling and piling on top of each other to create the
largest mountains on the world today. The Himalayan orogeny took between
40 and 60 million years, and is still continuing.
The crust beneath the Himalayan Mountains is between 60 and 780 km thick.
This is nearly twice as thick as continental crust over the rest of
the world. This thick crust forms what is termed a ‘crustal root’.
This root protrudes downward into the mantle and is important for mountains
because the buoyancy of the root allows the mountains to achieve their
Sunrise in the Himalayas
- View from Poone Hill, Nepal
of the Himalayas
The Indian plate is continuing to crash into the continent of Asia.
This is happening at an average rate of 2 cm/year, or 2 meters in the
next century. The result of this continuing geologic change is periodic
earthquakes in the Himalayas from accumulated energy from collision
and the continuing growth of the mountains. It is unlikely, however,
that the mountains will rise much farther. At present, the peak of Mount
Everest, the tallest mountain in the world, is 29,029 feet (8,848 m)
above sea level. Although the collision between India and Asia is continuing,
erosive forces are also working on the mountain and wearing down the
peaks. In addition, as the mountains continue to rise, their massive
weight bears down on the crustal root and the rock that is buried in
the crust. As this rock as pressed down into the mantle, it begins to
melt and flow slowly, and can be squeezed out to the side, causing the
mountain to collapse lower.
Global Positioning Systems (GPS) have been important
to the geologic research involving plate tectonics and the India-Eurasia
collision. It is GPS data that tell us how quickly the geologic change
is happening. Using this data, several theorists have put forth that
in the next 10 million years, India will plow forward another 150 -
200 km, roughly the width of the country of Nepal. This means that in
10 million years, Nepal as we now know it may no longer exist due to
the powerful geologic forces of our earth. Several scientists also believe
that the Himalayan region is due for some very powerful earthquakes
to relieve the stress created by collision on the Himalayan arc. It
is believed that a large earthquake in this region poses a serious threat
for over 50 million people.
Mt. Dhaulagiri (above), Mt. Everest (above, right)
Mt. Kanchenjunga (above), Mt. Machhapuchhre (above, right)
To see more pictures from my trek through the Himalayan
Pictures not referenced via links to original website
were taken by Marissa Pine, December, 2001
Creation/revision date: 20 March, 2003