The Himalayan Mountains in Tibet were formed from the movement of plates in the lithosphere.
The lithosphere, the Greek word for “rocky sphere”, is the outermost layer of the Earth. The term is also used to refer to the outermost rocky layer of other solid planets. It is a relatively thin layer, about 31 to 62 miles (50 to 100 km) thick under the oceans and 93 miles (150 km) thick on the continents. This layer is made up of the upper crust, about 3 miles (5 km) thick in the oceans and 40.3 mles (65 km) thick in the continents, and the upper mantle, which makes up the remainder. Separating the crust and upper mantle is the Mohorovičić discontinuity, the point at which rocks become more plastic than solid. Below the lithosphere is the asthenosphere, which continues the upper mantle and is approximately the point at which the mantle becomes liquid.
The lithosphere is the outermost layer of the Earth, separating the crust from the upper mantle.
This planetary shell consists of lithospheric plates, also known as plate tectonics, that move slowly over time periods of millions of years. Its rate of drift is comparable to the growth rate of a person’s nails. Over long periods of time, however, they can create powerful structures, like the Himalayan Mountains in Tibet. Mt. Everest and the other mountains were formed when the tectonic plate under India forced its way into Asia.
Australia split from Antarctica 50 million years ago, creating the circumpolar current.
Using careful measurement methods and the study of strata, paleontologists have determined that plate tectonics have spread across the planet’s surface since at least 600 million years ago, when several fossils appeared. During that time, the continents started apart, then merged into the giant continent Pangea, only to split after a few hundred million years and create the continents that people are familiar with today.
Geoscientists study the properties of the lithosphere by examining xenoliths.
Lithospheric activity can have a profound effect on the surface above it. When Australia finally broke away from Antarctica 50 million years ago, it allowed a new ocean current – the circumpolar current – to flow around Antarctica and reinforce its own cooling. This froze the continent, which was once covered in forests, killing all but the hardiest. It also decreased the global average temperature by several degrees.
While humans cannot dig very deep into the Earth’s crust with current technology, geoscientists can study the properties of the deep lithosphere by examining special rocks, or xenoliths, brought in by deep volcanic tubes.