core
the earth's center, made up of iron and nickel; the inner core is solid and the outer core is liquid.
mantle
a rock layer about 1,800 miles thick that is between the earth's crust and the earth's core.
magma
the molten rock material formed when solid rock in the earth's mantle or crust melts.
crust
the thin rock layer making up the earth's surface.
atmosphere
the layer of gases immediately surrounding the earth.
lithosphere
the solid rock portion of the earth's surface.
hydrosphere
the waters comprising the earth's surface, including oceans, seas, rivers, lakes, and vapor in the atmosphere.
biosphere
all the parts of earth where plants and animals live, including the atmosphere, the lithosphere, and the hydrosphere.
Continental Drift
the hypothesis that all continents were once joined into a supercontinent that split apart.
Hydrologic Cycle
the continuous circulation of water among the atmosphere, the oceans, and the earth.
Drainage Basin
an area drained by a major river and its tributaries.
ground water
the water held under the earth's surface, often in and around the pores of rock.
Water Table
the level at which rock is saturated.
landforms
a naturally formed feature on the surface of the earth.
steppes
a wide, treeless grassy plain.
savanna
the term for the flat, grassy, mostly treeless plains in the tropical grassland region.
prairie
a large, level area of grassland with few or no trees.
mountain
natural elevation of the earth's surface with steep sides and greater height than a hill.
valley
low land between hills or mountains.
glacier
a large ice mass that moves slowly down a mountain or over land.
cataract
a step-like series of waterfalls.
canyon
a narrow, deep valley with steep sides.
cliff
the steep, almost vertical edge of a hill, mountain, or plain.
plateau
a broad, flat area of land higher than the surrounding land.
mesa
a wide, flat-topped mountain with steep sides, larger than a butte.
oasis
a spot of fertile land in a desert, fed by water from wells or underground springs.
butte
a raised area of land with steep cliffs, smaller than a mesa.
swamp
a lowland region that is saturated by water.
flood plain
flat land near the edges of rivers formed by mud and silt deposited by floods.
island
a body of land surrounded by water.
volcano
an opening in the earth, usually raised, through which gases and lava escape from the earth's interior.
strait
a narrow channel connecting 2 larger bodies of water.
peninsula
a point of land extending into an ocean or lake.
sea level
level of the ocean's surface, used as a reference point when measuring the height or depth of the earth's surface.
bay
part of an ocean or lake partially enclosed by land.
harbor
a sheltered area of water deep enough for docking ships.
river mouth
the place where a river flows into a lake or an ocean.
marsh
soft, wet, low-lying, grassy land that serves as a transition between water and land.
delta
a triangular area of land formed from deposits at the mouth of a river.
Continental Shelf
the earth's surface from the edge of a continent to the deep part of the ocean.
relief
the difference in elevation of a landform from the lowest point to the highest point.
Topography
the combined characteristics of landforms and their distribution in a region.
Tectonic Plates
an enormous moving shelf that forms the earth's crust.
divergent boundary
a plate boundary where two plates move away from each other.
transform boundary
a plate boundary where two plates move past each other in opposite directions.
fault
fracture in the earth's crust.
earthquake
a sometimes violent movement of the earth, produced when tectonic plates grind or slip past each other at a fault.
seismograph
a device that measures the size of the waves created by an earthquake.
epicenter
the point on the earth's surface that corresponds to the location in the earth where an earthquake begins.
Richter scale
a way to measure info collected by seismographs to determine the relative strength of an earthquake.
tsunami
a giant ocean wave, caused by an underwater earthquake or volcanic eruption, with great destructive power.
volcano
a natural event, formed when magma, gases, and water from the lower part of the crust or mantle collect in underground chambers and eventually erupt and pour out of cracks in the earth's surface.
lava
magma that has reached the earth's surface.
Ring of Fire
the chain of volcanoes that lines the Pacific Rim.
weathering
physical and chemical processes that change the characteristics of rock on or near the earth's surface, occurring slowly over many years.
sediment
small pieces of rock produced by weathering processes.
mechanical weathering
natural processes that break rock into smaller pieces.
chemical weathering
a process that changes rock into a new substance through interactions among elements in the air or water and the minerals in the rock.
erosion
the result of weathering on matter, created by the action of wind, water, ice, or gravity.
loess
wind-blown silt and clay sediment that produces very fertile soil.
Glaciation
the changing of landforms by slowly moving glaciers.
moraine
a ridge or hill of rock carried and finally deposited by a glacier.
humus
organic material in soil.
Orographic Lifting
cloud formation that occurs when warm moist air is forced to rise up the side of a mountain