Collision Boundary or Fault:Two plates moving toward each other resulting in both plates pushing
upwards.
Convergent boundary:Place where two plates moving from different directions meet head-on. Both
collision and subduction faults are types of a converging boundary.
Continental drift:The Idea that continents move from one part of Earth to another.
Convection:Movement of a fluid because of density differences.
Convection Currents: movement within hot fluids, when the heat source is on the bottom, such as in a
boiling pot of soup on the stove. Convection currents happen because the hotter material is less dense
and rises; when it reaches the surface, it cools and becomes less dense, so it sinks. This rising and
sinking creates a circular motion within the fluid.
Core: The center region of the Earth
Crust: The very thin outer layer of Earth above the mantle, composed of a rigid layer of lighter rocks that
can extend 65 km at its deepest point
Density:Ratio between the mass and the volume of a substance, found by dividing an object's mass by
its volume.
Divergent boundary:Place where two plates of lithosphere are moving apart and new lithosphere is
formed.
Equator:Imaginary east-west line that circles Earth halfway between geographic poles.
Epicenter:Point on Earth's surface directly above an earthquakes focus.
Focus:The true location of an earthquake and source of seismic waves.
Harry Hess: Developed the theory of sea-floor spreading in 1960
Inner Core: The solid innermost layer of Earth, composed of iron and nickel under expremely high
pressure and temperature.
Latitude:Measurement of angular distance on the Earth north or south of the equator.
Lithoshpere:Solid outer layer of Earth including both crust and upper mantle.
Longitude:Measurement of angular distance on the Earth east or west of the prime meridian.
Magma:Melted rock beneath Earth's surface.
Magnetic Field: An area in which the motion of charged particles creates a magnetic force, such as the
field of magnetic force generated by the movement of fluid in Earth's outer core
Mantle: The thickest of the Earth's layers, located between the outer core and the Earth's crust,
composed mostly of compounds rich in iron, silicon, and magnesium
Mid-ocean Ridge:Long chain of underwater mountains.
Normal Fault:A fault where the rocks above the fault move down.
Outer Core: The layer of Earth's interior located between the inner core and the mantle, composed of
iron and nickel in a liquid state
Outer Mantle: Upper part of the Earth's mantle which contains both the lower part of the lithosphere and
the athenosphere
Pangaea: Name of the hypothetical great continent thought to have split into the landmasses known
today; a word coined by meteorologist Alfred Wegener from the Greek pan andgaie, meaning "all" and
"land".
Plate:Large moving section of lithosphere that contains continents and seafloor.
Plate tectonics:Theory that solid plates made of the lithosphere move on top of the putty like
asthenosphere.
Reverse fault:A fault where the rocks above the fault move up.
Richter scale:Numerical description of the size of seismic waves produced by an earthquake.
Ridge Push: A force that is exerted by cooling, subsiding rock on the spreading lithospheric plates at a
mid-ocean ridge
Rift:Deep valley which runs down the middle of a mid-ocean ridge.
Rift Valley: A deep valley at a point where lithospheric plates are moving apart, such as at a mid-ocean
ridge
Seafloor spreading:Theory that seafloor crust forms at mid-ocean ridges and then spreads in opposite
directions.
Seismic wave:Vibration produced by an earthquake
.
Seismograph:Instrument that measures and records seismic waves.
Shield cone:Volcanic mountain with a broad base and gently sloping sides, made from lava flows.
Slab Pull: A force at a subduction boundary that the sinking edge of the subducting plate exerts on the
rest of the plate.
Sliding boundary:Place where two plates meet and slide past each other. Also known as a transform
fault.
Strike-slip fault:Fault where the rocks on either side of the fault break and slide past each other.
Subduction:Pushing of the edge of one plate below the edge of another.
Subduction Boundary: A convergent boundary where an oceanic plate is plunging beneath another,
overriding plate
Transform Boundary or Fault:Place where two plates meet and slide past each other. Also known as a
sliding boundary.
Volcano: Opening in Earth's crust where melted rock reaches Earth's surface.