Plate tectonics is the theory that explains how the Earth's crust is divided into plates that move and change shape over geological time. The lithosphere consists of rigid tectonic plates that move atop the asthenosphere, a plastic layer of the upper mantle that flows slowly due to convection currents in the Earth's mantle. Heat from the interior rises at mid-ocean ridges, pushing crust outward and causing plates to move apart while cooler material sinks back into the mantle.
2. The theory that explains
how large pieces of the
crust, called plates, move
and change shape
3. Lithosphere – solid, outer
layer of the Earth that
consists of the crust and the
rigid upper part of the
mantle
Asthenosphere – the solid,
plastic layer of the mantle
that flows slowly
5. Convection – the movement
of hot, less dense material
up and cold, more dense
material down
6. • Interior of the Earth heats
the mantle which rises to
the surface at the Mid-
Ocean Ridges and pushes
the crust
• The remaining movement
of the mantle pulls the
plates with it underneath
• Cools into rock and
eventually sinks back into
the mantle where it is
melted and sinks due to
density and gravity
