Earth's Changing Surfaces

Terms	Definitions
Weathering	The chemical and physical processes that break down rock at Earth's surface
Erosion	The process by which water, ice, wind, or gravity moves weathered rock and soil
Uniformitarianism	The geological principle that the same geologic processes that operate today operated in the past to change Earth's surface
Abrasion	The grinding away of rock by other rock particles carried in water, ice, or wind
Chemical Weathering	The process that breaks down rock through chemical changes.
Causes of Chemical Weathering (Hint: There Are 5)	(1) Action of water; (2) Oxygen; (3) Carbon Dioxide; (4) Living Organisms; (5) Acid Rain
Mechanical Weathering	The type of weathering in which rock is physically broken into smaller pieces
Causes of Mechanical Weathering (Hint: There Are 5)	(1) Freezing and thawing; (2) Release of pressure; (3) Plant growth; (4) Actions of animals; (5) Abrasion
Deposition	Process in which sediment is laid down in new locations
Mass Movement	Any one of several processes by which gravity moves sediment downhill
Types of Mass Movement (Hint: There Are 4)	(1) Landslides; (2) Mudflows; (3) Slump; (4) Creep
Gravity	A force that moves rocks and other materials downhill
Sediment	Earth materials deposited by erosion. Sediment may consist of pieces of rock or soil or the remains of plants and animals.
Runoff	Water that flows over the ground surface rather than soaking into the ground
Flood Plain	Wide valley through which a river flows
Meander	A looplike bend in the course of a river
Oxbow Lake	A meander cut off from a river
Alluvial Fan	A wide, sloping deposit of sediment formed where a stream leaves a mountain range
Delta	A landform made of sediment that is deposited where a river flows into an ocean or lake
Groundwater	Water that fills the cracks and spaces in underground soil and rock layers
Stalactite	A calcite deposit that hangs from the roof of a cave
Stalagmite	A cone-shaped calcite deposit that builds up from the floor of a cave
Glacier	A large mass of moving ice and snow on land
Continental Glacier	A glacier that covers much of a continent or large island
Valley Glacier	A long, narrow glacier that forms when snow and ice build up in a mountain valley
Ice Age	Times in the past when continental glaciers covered large parts of Earth's surface
Plucking	The process by which a glacier picks up rocks as it flows over the land
Till	The sediments deposited directly by a glacier
Moraine	A ridge formed by the till deposited at the edge of a glacier
Kettle	A small depression that forms when a chunk of ice is left in glacial till
Headland	A part of the shore that sticks out into the ocean
Beach	Wave-washed sediment along a coast
Longshore Draft	The movement of water and sediment down a beach caused by waves coming in to shore at an angle
Spit	A beach formed by longshore drift that projects like a finger out into the water
Sand Dune	A deposit of wind-blown sand
Deflation	Wind erosion that removes surface materials
Loess	A wind-formed deposit made of fine particles of clay and silt