geology
The study of planet Earth.
rock
The material that forms the Earth's hard surface.
constructive forces
Forces that build up mountains and landforms on the Earth's surface.
destructive forces
Forces that slowly wear away mountains and other features on the surface of Earth.
continents
Great landmasses surrounded by oceans
seismic waves
Vibrations that travel through Earth carrying the energy released during an earthquake.
pressure
The amount of force pushing on a surface or area.
crust
The layer of rock that forms the Earth's outer surface.
basalt
A dark, dense, igneous rock with a find texture, found in oceanic crust.
granite
A usually light-colored rock that is found in continental crust.
mantle
The layer of hot, solid material between Earth's crust and core.
lithosphere
A rigid layer made up of the uppermost part of the mangle and the crust.
asthenosphere
The soft layer of the mantle on which the lithosphere forms.
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 in the center of Earth.
magnetic field
Magnetism of the Earth caused by the core spinning faster than the rest of the planet.
heat transfer
The movement of energy from a warmer object to a cooler object.
radiation
The transfer of energy through empty space.
conduction
The transfer of heat by direct contact of particles of matter.
convection
The transfer of heat by movements of a heated fluid.
density
The amount of mass in a given space; mass per unit volume.
convection current
The movement of a fluid, caused by differences in temperature, that transfers heat from one part of the fluid to another.
continental drift
The hypothesis that the continents slowly move across the Earth's surface.
Alfred Wegener
Scientist who hypothesized that all the continents were one joined together in a single land mass.
fossil
A trace of an ancient organism that has been preserved in rock.
mid-ocean ridge
The undersea mountain chain where new ocean floor is produced; a divergent plate boundary.
Harry Hess
An American geologist who discovered sea floor spreading by using sonar.
sonar
A device that determines the distance of an object under water by recording echoes of sound waves.
molten
Rock that is so hot it has become fluid.
sea-floor spreading
The process by which molten material adds new oceanic crust to the ocean floor.
magnetic stripes
Sections of the sea floor that appear in stripes of alternating magnetic directions.
magnetic memory
Rocks that record the direction of the Earth's magnetic poles at the time they formed.
deep-ocean trenches
Deep valleys along the ocean floor through which oceanic crust slowly sinks towards the mantle.
subduction
The process by which oceanic crust sinks beneath a deep-ocean trench and back into the mantle at a convergent plate boundary.
continental crust
Type of crust found on Earth's continents; mostly made of granite, which is less dense and light.
oceanic crust
Type of crust found under Earth's oceans; mostly made of basalt, which is dense and heavy.
plates
A section of the lithosphere that slowly moves over the asthenosphere, carrying pieces of continental and oceanic crust.
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.
plate boundaries
Places where two or more plates meet.
faults
A break in the Earth's crust where slabs of rock slip past each other.
transform boundaries
A plate boundary where two plates move past each other in opposite directions.
divergent boundaries
A plate boundary where two plates move away from each other.
rift valley
A deep valley that forms where two plates move apart.
convergent boundaries
A plate boundary where two plates move toward each other.
Pangaea
The name of the single landmass that broke apart 200 million years ago and gave rise to today's continents.
Laurasia
The name of the northern supercontinent that formed after the breakup of Pangaea; included North America, Europe, and Asia.
Gondwana
The name of the southern supercontinent that formed after the breakup of Pangaea; included South America, Africa, Antarctica, India, and Australia.