asthenosphere
the soft layer of the mantle on which the lithosphere floats
basalt
A dark, dense, igneous rock with a fine texture, found in oceanic crust
conduction
the direct transfer of heat from one substance to another substance that it is touching
continental drift
the hypothesis that the continents slowly move across Earth's surface
convection
the transfer of heat by the movement of a fluid
crust
the layer of rock that forms Earth's outer surface
seismic waves
vibrations that travel through Earth carrying the energy released during an earthquake
pressure
the result of a force distributed over an area
granite
A usually light colored igneous rock that is found in continental crust
mantle
the layer of hot, solid material between Earth's crust and core
lithosphere
the solid, outer layer of the earth that consists of the crust and the rigid upper part of the mantle
outer core
a layer of molten iron and nickel that surrounds the inner core of Earth
inner core
a dense sphere of solid iron and nickel at the center of Earth
radiation
the transfer of energy through space
density
the amount of matter in a given space; mass per unit volume
convection currents
Circular currents in the mantle caused by the magma being heated by the core off the Earth.
Pangea
large supercontinent that existed 250 million years ago
fossil
the trace or remains of an organism that lived long ago, most commonly preserved in sedimentary rock
mid-ocean ridge
an underwater moutain chain where new ocean floor is formed
sonar
a measuring instrument that sends out an acoustic pulse in water and measures distances in terms of the time for the echo of the pulse to return
sea-floor spreading
Hess's theory that new seafloor is formed when magma is forced upward toward the surrface at a mid-ocean ridge.
deep-ocean trench
a deep valley along the ocean floor through which oceanic crust slowly sinks toward the mantle.
subduction
a geological process in which one edge of a crustal plate is forced sideways and downward into the mantle below another plate
plate
a rigid layer of the Earth's crust that is believed to drift slowly
scientific theory
A well tested concept that explains a wide range of observations
plate tectonics
the theory that pieces of Earth's lithosphere are in constant motion, driven by convection currents in the mantle
fault
surface along which rocks move when they pass their elastic limit and break
divergent boundary
a plate boundary where two plates move away from each other
rift valley
A deep valley that forms where two plates move apart.
convergent boundary
a plate boundary where two plates move toward each other
transform boundary
when two tectonic plates slide past each other horizontally