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16 terms

Chapter 12 Vocabulary

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Asthenosphere
weaker, semi-solid, plastic-like layer beneath Earth's lithosphere on which lithospheric plates move
Cinder cone volcano
small, violently erupting volcano formed by accumulation of large pyroclastic materials around a vent
Composite volcano
large volcano formed by alternating lava flows and violently erupting pyroclastic materials
Convergent boundary
plate tectonic boundary where lithospheric plates collide
Discontinuity
boundary marking an abrupt density change between Earth's layers
Divergent boundary
plate tectonic boundary where lithospheric plates are moving apart
Elastic rebound
sudden energy release that accompanies fault movement and causes earthquakes, or seismic vibrations
Epicenter
point on Earth's surface directly above an earthquake's center
Fault
crack in Earth's crust along which movement has taken place
Focus
pint of origin of an earthquake
Mid-ocean ridge
a system of twin mountain ranges with a rift valley between them that extends around Earth on the sea-floor; formed where two oceanic plates are force apart due to magma rising from Earth's mantle; a source of new rock
Rift valley
long, linear, dropped-down valley between twin, parallel mountain ranges produced by faulting
Shadow zone
"dead zone" between 105 and 140 degrees from an earthquake's epicenter, where nothing is recorded on a seismogram
Subduction
occurs when lithospheric plates converge and the edge of one plate is forced downward beneath another; recycles old lithospheric plates
Transform boundary
plate tectonic boundary that exists as a large fault, or crack, along which lithospheric plates move in a horizontal direction
Viscosity
a fluid's resistance to flow