About 225 million years ago, India was a large island still situated off the Australian coast, and a vast ocean (called Tethys Sea) separated India from the Asian continent. When Pangaea broke apart about 200 million years ago, India began to forge northward. By studying the history -- and ultimately the closing-- of the Tethys, scientists have reconstructed India's northward journey. About 80 million years ago, India was located roughly 6,400 km south of the Asian continent, moving northward at a rate of about 9 m a century. When India rammed into Asia about 40 to 50 million years ago, its northward advance slowed by about half. The collision and associated decrease in the rate of plate movement are interpreted to mark the beginning of the rapid uplift of the Himalayas.
Fifty kilometers north of Lhasa (the capital of Tibet), scientists found layers of pink sandstone containing grains of magnetic minerals (magnetite) that have recorded the pattern of the Earth's flip-flopping magnet
Fifty kilometers north of Lhasa (the capital of Tibet), scientists found
layers of pink sandstone containing grains of magnetic minerals (magnetite)
that have recorded the pattern of the Earth's flip-flopping magnetic field.
These sandstones also contain plant and animal fossils that were deposited
when the Tethys Sea periodically flooded the region. The study of these
fossils has revealed not only their geologic age but also the type of environment
and climate in which they formed. For example, such studies indicate that
the fossils lived under a relatively mild, wet environment about 105 million
years ago, when Tibet was closer to the equator. Today, Tibet's climate
is much more arid, reflecting the region's uplift and northward shift of
nearly 2,000 km. Fossils found in the sandstone layers offer dramatic evidence
of the climate change in the Tibetan region due to plate movement over the
past 100 million years.
The Himalayas: Two continents collide