Geology Chapter 3 Vocab

Asthenosphere

the weak layer of the upper mantle, below the lithosphere.

Brittle deformation

a type of deformation during which rocks respond to stress by breaking.

Compressive stress

a type of stress that compresses or squeezes rocks.

Continental drift

the concept that the continents were once together and have drifted to their present position.

Continental rifting

the first stage in the process of divergence, during which a continent is broken by tensional stress.

Continental volcanic arc

a chain of volcanoes on a continent that is formed by oceanic-continental convergence.

Convergent plate boundary

a plate boundary where two plates move toward each another.

Crust

the thin top layer of the earth, above the mantle; it is made of rock and is subdivided into the thinner basaltic oceanic crust and the thicker granitic continental crust.

Divergent plate boundary

a plate boundary where two plates move apart. This is where seafloor spreading occurs.

Elastic deformation

a type of deformation that is temporary and in which the object under stress goes back to its original shape once the stress has been removed.

Hot spot

a center of volcanic activity that originates deep into the Earth and is not necessarily associated with a plate boundary.

Island arc

a chain of volcanic islands that form by oceanic-oceanic convergence.

Lithosphere

the brittle top layer of the Earth, above the asthenosphere, and that comprises the crust and the top of the mantle. The plates are made of lithosphere.

Mantle

the layer of the Earth that is between the crust and the core; it is made of silicates and is rich in iron and magnesium.

Mid-oceanic ridge

a ridge that is volcanically and seismically active, located under water in the middle of the major oceans,and is the site of seafloor spreading.

Oceanic trench

a narrow deep depression on the seafloor, where one plate bends and subducts beneath another plate.

Plastic deformation

a type of deformation that is permanent and in which the materials flows like silly putty.

Plate tectonics

the concept that the Earth's lithosphere is broken into segments (plates) that move.

Seafloor spreading

the process by which new lithosphere is made at mid-ocean ridges and recycled at oceanic trenches.

Shearing stress

a type of stress that causes different parts of an object to slide past each other in opposite directions.

Strain

another word for "deformation;" is the result of stress.

Stress

a force applied to an object.

Subduction zone

where a lithospheric plate bends and goes back down into the Earth.

Tectonics

the study of large-scale movement and deformation of the Earth's crust.

Transform fault boundary

a plate boundary where two plates slide horizontally in opposite directions.

Volcanic island arc

see "island arc" above