2 23.1 Fresh Water Earth is 71% water 97% is salt water 3% is freshwater Most freshwater is in the form of groundwater- water found underground in cracks and between particles of rock and soil.Some freshwater is found in lakes, streams, water vapor, and clouds.
3 The Water CycleThe water cycle is made up of several processes, including evaporation, transpiration, condensation, precipitation, and the eventual return of flowing water to the ocean.Evaporation- liquid to vapor (gas)Transpiration- when water vapor is released from the leaves of trees and other plantsCondensation- when water vapor expands and cools, water vapor forms droplets which crystallize at lower temperaturesPrecipitation- when water droplets or ice crystals get too heavy, they fall as rain, sleet, snow, hail, or freezing rain
4 Fresh WaterA small portion of Earth’s fresh water is located in the atmosphere, streams, and lakes. Most is located in groundwater and glaciers.Glaciers- large masses of moving ice and snow on landRunoff- water that flows over Earth’s surface, goes into streamsTributary- smaller stream that flows into a larger riverWatershed- area of land that contributes water to a river system (Rocky Mountains to Appalachian)Saturated zone- region where the pore spaces are entirely filled with groundwaterWater table- top of saturated zonePermeable- water can pass throughAquifer- permeable rock saturated with waterImpermeable- water cannot pass through
5 23.2 Weathering and Mass Movement Erosion- the process that wears down and carries away rock and soilErosion acts through weathering, the force of gravity, and through the movement of streams, groundwater, glaciers, wind, and waves.Erosion forms canyons, caves
6 WeatheringWeathering is the process by which rocks are chemically altered or physically broken down into fragments at or near Earth’s surfaceThere are two forms of weathering: mechanical and chemical. They cause rocks to disintegrate or decompose.Mechanical weathering- process of physically breaking rock into smaller fragmentsAbrasion- rocks scrape or grind against one anotherChemical weathering- process in which rock is broken down by chemical reactions, such as water, acid, and oxidation
7 Rates of WeatheringThe rate at which mechanical and chemical weathering take place depends on three main factors: temperature, the availability of water, and the type of rock.High temperature and abundant rainfall lead to a higher rate of weathering.Limestone and marble rapidly weather.
8 Mass MovementMass movement- the downward movement of rock and soil due to gravityThrough the process of mass movement, gravity moves loose material down a slope.Landslide- rapid movement of large amounts of rock and soilMudflow- rapid mass movement of soil and other sediment mixed with waterCreep- soil gradually moves down a slope (caused from ice)Slump- weak layers of soil or rock suddenly move downslope as a single unit
9 23.3 Water Shapes the LandDeposition- the process in which sediment is laid down in new locations, usually by flowing waterSaltation- process of particles bouncing along a stream bottomA stream’s ability to erode depends mainly on its speed.
10 Features Formed by Water Erosion Water erosion forms V-shaped valleys, waterfalls, meanders, and oxbow lakes.V-shaped valley- contains rapids and waterfalls, occur at stream’s sourceFlood plain- flat area along a stream that is entirely covered only during times of floodMeander- slight curving of river, looks like a loopOxbow lake- a separate, curved lake formed when sediments cut off river
11 Features Formed by Water Deposition Features deposited by flowing water include alluvial fans and deltas.Alluvial fan- when a stream flows out the mountains and onto plains, it slows down, sediments settle, and a fan-shaped deposit of sediment is leftDelta- a mass of sediment deposited where a river enters a large body of water
12 Groundwater ErosionThe processes of chemical weathering causes much groundwater erosion, including the formation of caves and sinkholes.Stalactite- on cavern ceiling, icicle-like formationStalagmite- pillar of minerals on cavern floorSinkhole- weakened limestone can collapse suddenly
13 23.4 Glaciers and WindGlaciers form in places where more snow falls than melts or sublimates.Continental glacier- thick sheet of ice that covers a huge area, such as a continent or large islandValley glacier- glacier that occurs in a high mountain valleyPlucking- glacial ice widens cracks in bedrock beneath the glacierGlaciers cause many distinctive features in the landscape, including cirques, horns, U-shaped valleys, and glacial lakes
14 Cirque- valleys formed from valley glaciers When a glacier melts, it deposits its load of sediment, creating a variety of landforms.Till- glacial sedimentMoraine- mound of sediment at the downhill end of the glacier and along its sides, formed by till
15 Wind Erosion and Deposition Wind erodes the land by deflation and abrasion.Deflation- wind picks up and carries away loose surface materialAbrasion- wind blows sand against other rocks, sandblastingFeatures deposited by wind include sand dunes and loess depositsDune- deposit formed from windblown sandLoess (less)- deposit formed from windblown dust
16 23.5 The Restless OceansSalinity- the proportion of dissolved salts in water (35g/kg water)Light and temperature decrease with depth, whereas pressure increases.Continental shelf- gently sloping plain forms an apron of shallow water along the edges of most continentsSurface current- large stream of ocean water that moves continuously in about the same path.Winds blowing across the surface of the ocean cause the continuous flow of surface currentsDeep ocean currents are caused by differences in the density of ocean waterUpwelling- movement of water from the deep ocean to the surfaceIn upwelling, winds blow warm surface water aside. This allows cold water from the deep ocean to rise and take the place of the warmer water.Two physical processes, hydraulic action and abrasion, are responsible for much wave erosionLongshore drift- the process that moves sand along a shore
17 23.6 Earth’s HistoryRelative age- of a rock is compared to the ages of other rocks above or below it in a sequence of rock layersLaw of superposition- if rock layers are undisturbed, younger rocks lie above older rocks, and the oldest rocks are at the bottomGeologists use the law of superposition to determine the relative ages of sedimentary rocks from the sequence of rock layers and the fossils within each layer.Extinct- no longer existsIndex fossil- easily identified, occurred over a large area, and lived during a well-defined period of timeAbsolute age- time that has passed since the rock formed, determined by radioactive dating
18 A Brief History of Earth Era- major stage in Earth’s historyPeriod- smaller unit of eraMass extinction- when many creatures die in a short timePrecambrian time- 4.6 Billion to 544 Million years ago, Earth was formed, one-celled organismsPaleozoic Era- 544 to 248 Million years ago, clam and worm, fish, floodMesozoic Era- 248 to 65 Million years ago, dinosaursCenozoic Era- 65 Million years ago to now, ice age, mammals, humans