Science-Chapter 2

Earth's Layers

The four main layers: crust, mantle, outer core, and inner core.

Plate Tectonics

Theory that Earth's crust is broken into moving plates driven by mantle convection.

Water Cycle

Continuous movement of water through evaporation, condensation, precipitation, and collection.

Weathering

The physical or chemical breakdown of rocks at or near Earth's surface.

Erosion

The movement of weathered rock and soil by wind, water, ice, or gravity.

Glacier

A large, long-lasting mass of ice moving slowly under its own weight.

Plucking

Process where glaciers freeze to and pull up rocks from the bedrock.

Abrasion

Scraping of bedrock by rocks frozen into the bottom of a moving glacier.

U-Shaped Valley

A steep-sided valley carved out by the movement of a glacier.

Moraine

A ridge or pile of sediment and rock debris left behind by a melting glacier.

Till

Unsorted rock material deposited directly by a melting glacier.

Cirque

A bowl-shaped basin carved into a mountain by the head of a glacier.

Arête

A sharp, knife-edge ridge formed between two adjacent glaciated valleys.

Horn

A steep, pyramid-shaped mountain peak carved by multiple glaciers.

Fjord

A long, steep-sided glacial valley flooded by ocean water.

Wave-Cut Cliff

A cliff formed by waves eroding the base of a rocky coast.

Sea Cave

A hollow area formed by waves carving into a weak part of a sea cliff.

Sea Arch

A natural arch formed when waves erode completely through a sea cave.

Sea Stack

A pillar of rock remaining when the top of a sea arch collapses.

Longshore Drift

The movement of sand and sediment down a beach caused by waves hitting the coast at an angle.

Spit

A beach formed by longshore drift that projects like a finger out into the water.

Barrier Island

A long, narrow island lying parallel and close to the mainland, protecting the coast from erosion.

Wave Crest

The highest part of a wave.

Beach

An area of wave-deposited sediment along the coast.

Sandbar

An underwater ridge of sand built up by waves offshore.

Groin

A wall built perpendicular to the shore to trap sand and reduce erosion.

Runoff

Water that flows over the ground surface rather than soaking into the ground.

Tributary

A stream or river that flows into a larger river.

Watershed

The land area that supplies water to a river system.

Meander

A looplike bend in the smooth-flowing stream or river.

Oxbow Lake

A meander that has been cut off from the river and holds standing water.

Delta

A landform made of sediment deposited where a river flows into an ocean or lake.

Alluvial Fan

A wide, sloping deposit of sediment formed where a stream leaves a mountain range.

Rill

A tiny groove in soil formed by running water.

Gully

A large groove or channel in soil carved by runoff.

Waterfall

A vertical drop in a stream or river formed by differential erosion of rock layers.

Sinkhole

A depression formed when acidic groundwater dissolves underground rock, causing collapse.

Karst Topography

A landscape characterized by sinkholes, caves, and underground drainage systems formed by dissolving rock.

Cave

An underground chamber formed when acidic groundwater dissolves soluble rock like limestone.

Stalactite

An icicle-shaped mineral deposit that hangs from the ceiling of a cave.

Stalagmite

A mineral deposit that builds up from the floor of a cave.

Groundwater

Water held underground in soil and in pores and crevices in rock.

Atmosphere

The relatively thin layer of gases that forms Earth's outermost layer.

Convection Currents

Heat transfer in the mantle that drives the movement of tectonic plates.

Biosphere

The parts of Earth where life exists, including all living organisms.

Geosphere

The solid part of Earth, including rocks, minerals, and landforms.

Hydrosphere

All the water on Earth's surface, underground, and in the atmosphere.

Constructive Forces

Forces that build up Earth's surface, such as mountain building, volcanism, and deposition.

Deposition

The process where sediments are dropped in a new location, building up new landforms.

Seismic Waves

Vibrations generated by earthquakes that travel through Earth and provide primary evidence of its interior structure.

Earth's Magnetic Field

A field generated by convection currents in the liquid outer core, serving as evidence of fluid motion deep inside Earth.

Three Parts of the Mantle

lithosphere, asthenosphere, mesosphere