This is a drawing of a slab of lithosphere undergoing subduction.
Click on image for full size
Image copyright 1997 by the American Geophysical Union. Further electronic distribution is not allowed.
When two sections of the Earth's lithosphere collide one slab of lithosphere can be forced back down into the deeper regions of the Earth, as shown in this diagram. This process is called subduction. The slab that is forced back into the Earth usually undergoes re-melting when the edges reach a depth which is hot enough. (Temperatures hot enough to melt lithosphere are of the order of a thousand degrees!). The processes of mountain building or island formation, and lithospheric subduction usually go together, as shown in this picture of the Pacific Ocean floor.
Associated with the subduction of a slab of lithosphere is a trench, which is found at the interface between the slab which is undergoing subduction, and the adjoining slab. The trenches associated with subducting slabs can readily by seen on this diagram of a mid-ocean spreading ridge, and on maps of the ocean floor.
Remelted lithosphere is usually of a different chemical nature than the surrounding lithosphere or aesthenosphere. Remelted lithosphere rises back towards the surface where it frequently contributes to the formation of volcanoes and island arcs. The remelted lithosphere also releases gases of the atmosphere which had become trapped in the ground. Thus subduction of the lithosphere contributes to recycling of the atmosphere.
Shop Windows to the Universe Science Store!
Our online store
includes issues of NESTA's quarterly journal, The Earth Scientist
, full of classroom activities on different topics in Earth and space science, as well as books
on science education!
You might also be interested in:
Mountains are built through a general process called "deformation" of the crust of the Earth. One example of deformation comes from the process of subduction. When two sections of the Earth's lithosphere...more
As the Earth cools, hot material from the deep interior rises to the surface. Hot material is depicted in red in this drawing, under an ocean shown in blue green. The hotter material elevates the nearby...more
Earth’s center, or core, is very hot, about 9000 degrees F. This heat causes molten rock deep within the mantle layer to move. Warm material rises, cools, and eventually sinks down. As the cool material...more
Many kinds of surface features provide evidence of a sliding lithosphere. When two plates move apart, rising material from the mantle pushes the lithosphere aside. Two types of features can form when...more
Many forces cause the surface of the Earth to change over time. However, the largest force that changes our planet's surface is the movement of Earth's outer layer through the process of plate tectonics....more
Volcanoes form when hot material from below risesand leaks into the crust. This hot material, called magma, comes either from a melt of subducted crustal material, which is light and buoyant after melting,...more
The Abyss is a dark, deep place, but it's no longer hidden. At least when Nereus is on the scene. Nereus is a new type of deep-sea robotic vehicle, called a hybrid remotely operated vehicle (HROV). Nereus...more