faults
A break or crack in Earth's lithosphere along which the rocks move.
earthquakes
The shaking that results from the movement of rock beneath Earth's surface.
volcanoes
A weak spot in the crust where magma has come to the surface.
plate tectonics
The theory that pieces of Earth's lithosphere are in constant motion, driven by convection currents in the mantle.
convection currents
The movement of magma in the mantle caused by a cycle of uneven heating as warmer magma rises and cooler magma sinks.
continental drift
The hypothesis that the continents slowly move across Earth's surface.
convergent boundary
A plate boundary where two plates move toward each other.
subduction zone
The process where oceanic crust sinks underneath a continental crust and back into the mantle.
divergent boundary
A plate boundary where two plates move away from each other like at the mid-ocean ridge.
seafloor spreading
The process where molten magma adds new oceanic crust to the ocean floor at divergent boundaries.
transform boundary
A plate boundary where two plates move horizontally past each other in opposite directions.
Ring of Fire
Zone where most earthquake and volcanic activity surrounds the Pacific Ocean.
latitude
An imaginary line around the Earth parallel to the equator.
longitude
Distance in degrees east or west of the Prime Meridian.
Pangaea
Supercontinent; the single landmass that existed more than 250 million years ago and moved to where the continents are today.
weathering
The chemical and physical processes that break down rock at Earth's surface.
mechanical weathering
Process that breaks down rocks and minerals into smaller pieces but does not involve any change in their chemical makeup.
ice wedging
An example of mechanical weathering as rock splits when water seeps into cracks, then freezes and expands.
chemical weathering
Occurs when chemical reactions dissolve the minerals in rocks or change them into different minerals.
erosion
The process of moving sediments from one location to another.
deposition
Dropping of sediments that occurs when an agent of erosion such as gravity, glacier, wind or water loses its energy and can no longer carry the sediment.
mass movement
Any type of erosion that occurs as gravity moves materials down a slope such as mudflows, landslides or rockslides.