| A | B |
|---|
| groundwater | the water found underground within the cracks and between particles of rock and soil |
| water cycle | the continuous movement of water |
| transpiration | water vapor that enters the atmosphere when it is released from the leaves of trees and other plants |
| glacier | a large mass of moving ice or snow on land |
| runoff | water that flows over the Earth's surface |
| tributaries | the smaller streams that run into major rivers |
| watershed | the area of land that contributes water to a river system |
| saturated zone | a region where the pore spaces are entirely filled with groundwater |
| water table | the top the the saturated zone |
| permeable | something that water can pass through easily |
| aquifer | a permeable rock layer that is saturated with water |
| impermeable | something that water can not pass through easily |
| erosion | the process that wears down and carries away rock and soil |
| weathering | the process by which rocks are chemically altered or physically broken down into fragments at or near Earth's surface |
| mechanical weathering | the process of physically breaking rock into smaller fragments |
| abrasion | a form of mechanical weathering that occurs when rocks scrape or grind against one another |
| chemical weathering | a process in which rock is broken down by chemical reactions |
| mass movement | the downward movement of rock and soil due to gravity |
| deposition | the process in which sediment is laid down in new locations |
| saltation | the process of particles bouncing along a stream bottom |
| flood plain | the flat area along a stream that is entirely covered only during times of flood |
| meander | the looplike bend in a river formed when a slow-moving water deposits sediment on the inside curve of the river |
| oxbow lake | a lake formed when a river forms a new path by cutting off a meander loop from the rest of the river |
| alluvial fan | a fan-shaped deposit of sediment, on land formed as a stream flows out of the mountains and onto a plain |
| delta | a mass of sediment deposited where a river enters a large body of water |
| stalactite | an icicle-like formation formed by water dripping from the ceiling of a cavern |
| stalagmite | a pillar of minerals formed when water drips down to the floor of a cavern |
| sinkhole | a hole that results when erosion weakens a layer of limestone, causing protions of the ground to suddenly collapse |
| continental glacier | a thick sheet of ice that covers a huge area, such as a continent of large island |
| valley glacier | a glacier that occurs in a high mountain valley |
| plucking | glacial ice widens cracks in bedrock beneath the glacier |
| cirques | a large bowl shaped valley carved out of the mountain side |
| till | glacial sediment |
| moraines | mounds of sediment at the downhill end of the glacier and along its sides |
| deflation | the process that occurs when wind picks up and removes surface material |
| dunes | deposits formed from windblown sand |
| loess | a deposit formed from windblown dust |
| salinity | the proportion of disolved salts in water |
| continental shelf | the gently sloping plain that froms an apron of shallow water along the edges of most continents |
| surface current | a large stream of ocean water that moves continuously in about the same path |
| density current | currents caused by differences in the density of ocean water |
| upwelling | the movement of water from the deep ocean to the surface |
| hydraulic action | the process which occurs when waves pound on cracks in rocks |
| longshore drift | the process that moves sand along the shore |
| fossils | the preserved remains or traces of once living things |
| relative age | the age of a rock compared to the ages of other rocks above or below it in a sequence of rock layers |
| law of superposition | states that if rock layers are undisturbed, younger rocks lie above older rocks, and that the oldest rocks are at the bottom |
| extinct | an organism that no longer exists |
| index fossils | fossils of organisms that are easily identifies, occurred over a large area, and lived during a well-defined period of time |
| absolute age | the time that has passed since the rock formed |
| era | one major stage in the Earth's history |
| periods | a smaller unit of geologic time, a part of an era |
| mass extinction | a boundary between geologic eras when many different kinds of organisms became extinct within a relatively short time |
