Water cycle
•Also called the Hydrologic Cycle •Process by which water circulates between the Earth’s oceans, atmosphere, and land •Involves water storage, evaporation, transpiration, condensation, precipitation, and runoff. Water Storage •Oceans – super storage for the water cycle - holds 96.5% of Earth’s water •Primary pathway into the water cycle •Oceans, seas, lakes ,and rivers provide nearly 90% of the moisture in our atmosphere through evaporation. Evaporation •Process by which water changes from a liquid to a gas •Primary pathway that water moves from the liquid state back into the water cycle as water vapor •Heat (energy) from the sun is necessary for evaporation to occur. •Energy breaks bonds that hold water molecules together. •Molecules move fast at boiling point 212o F •Slow at freezing point 32o F •Sublimation – the process of snow and ice changing into water vapor without first melting into water. •Evapotranspiration – water lost to the atmosphere from the ground surface and transpiration of groundwater by plants through their leaves. Water Storage Atmosphere •Superhighway used to transport water around the globe •Involves condensation and precipitation Condensation •Process in which water vapor in the air is changed into liquid water. •Loss of energy allows water molecules to bond. Forms clouds, fog Precipitation •Water released from clouds in the form of rain, freezing rain, sleet, snow and hail •Provides the delivery system of atmospheric water to the Earth Water Storage Ice, snow, groundwater •Water locked up in its present state for a relatively long period of time •Involves runoff and infiltration Runoff •Precipitation that did not get absorbed into soil, or evaporate •Ice caps and glaciers - provides runoff from melting •Water moved by gravity makes its way into places that collect water – rivers, lakes, ponds, ocean Infiltration •The downward process of moving water from the land surface into soil or porous rock •Groundwater - Large amounts of water stored in the ground •Aquifer – another name for groundwater, usually describes water bearing formations Watershed •The area of land where all the water that falls in it and drains off of, goes into the same place •Can be as small as a footprint or as large as all the land that drains water into the Mississippi River Weathering
•Chemical and physical breakdown of rocks into sediment •Occurs when the rock’s environment changes and the rock is exposed to some form of water and the air Chemical Weathering Chemical change within the rock’s minerals breaking down the bonds holding the rocks together, causing them to fall apart into smaller pieces. Causes rock to break: •(A) Oxidation – Iron combines with oxygen making rust. •(B) Hydrolysis – Water softens minerals in rocks. •(C) Carbonation – Carbon dioxide in rain water creates carbonic acid. Ex. acid rain, cave creation Physical (Mechanical) Weathering The process that breaks rocks apart without changing their chemical composition caused by: Glacial/Ice: •(A1) Abrasion - by rapidly moving water, glaciers or wind. •(A2) Ice wedging - by freezing and thawing (contracting and expansion). Causes rock to break: •(B) Plant Roots - grow into cracks and break apart rock. •(C) Burrowing – animals scrape and dig the terrain. •(D) Temperature Change- cold to hot expanding and contracting. •(E) Gravity - falling rocks or debris, compression Erosion The process that moves bits of rock or soil from one place to another by: •Gravity •Water (rivers, waves) •Wind •Ice (glaciers) Deposition The process in which sediments, soil, and rocks are added to a landform such as: •Deltas •Flood plains •Sandbars •Dunes Occurs when the forces moving sediments are no longer able to overcome the forces of gravity and friction. Running water is the primary agent of erosion. •Velocity (speed) depends on gradient (slope) and discharge (amount of water). •As velocity increases the size of particles carried also increases. Ages of Rivers •(A) Young Rivers - fast-flowing, V-shaped valleys, waterfalls, and rapids •(B) Mature rivers – Less energy, slower, meanders (1), sandbars •(C) Old River – Very slow, shallow, large amounts of sediment deposited, many narrow channels, islands, deltas (2) Features Created by Wind Caused by abrasion from wind blown sand. •Arches •Sand dunes Mushroom Rocks Features Created by Gravity Gravity shapes the Earth’s surface by moving weathered material from a higher place to a lower one. •(A) Landslides (fast) •(B) Mud flows •(C) Slump/creep (slow) Features Created by Glaciation Caused as massive glaciers flow down hill bulldozing existing rocks. •U-Shaped Valley •Hanging Valley •Horn •Moraine •Cirque •Tarn lake •Arête Features Created by water (waves) Erosional and depositional features which form along coastlines •The western U.S. coastline has more erosional features. •The eastern U.S. coast and the Gulf of Mexico has more depositional features. Ecoregions of the United States Areas defined by its environmental conditions, especially climate, landforms, and soil characteristics. Ecoregions Environmental Conditions •Climate – weather conditions in an area over time. •Tropical •Arid •Mediterranean • Landforms – crustal material •Mountains – high elevation •Plateaus – medium to high elevation •Plains – low elevation •Soil characteristics •Amount of vegetation •Dry (arid) – very little vegetation (poor soil) Humid – large amount of vegetation (good soil) Examples of Ecoregions •Subtropical (Florida, South Eastern States) •Tundra (N Alaska) •Temperate Steppe (Great Plains •Marine Mountains (Coastal Washington and Oregon) •Desert and Desert Mountain (Nevada and parts of New Mexico) What determines how the processes of weathering, erosion, and deposition work to reshape Earth’s surface? •Rivers •Rock formations •Soils •Topography •Precipitation |
Erik E. Mason
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