Surface Processes on Earth Unit 5

Weathering and Erosion Weathering is the process of breaking down rocks at or near the Earth’s surface. Erosion is the movement of sediments from one place to another.

Weathering

MECHANICAL WEATHERING Doesn’t change the rock CHEMICALLY Types of mechanical weathering – FROST/ICE WEDGING: repeated thawing and freezing of water in cracks of rocks – UPLIFTING: when layers of rock above are removed, the release of PRESSURE allows the rock to expands and cracks – Plant growth into cracks can split open rocks – EXFOLIATION: the action of EXFOLIATION allows outer rock layers to be striped away

CHEMICAL WEATHERING Occur when CHEMICAL REACTIONS take place within the rock – Eroded sediments are different chemically – Increases with SURFACE AREA Water, oxygen, carbon dioxide and acids can cause chemical weathering Water = hydrolysis. Occurs in Silicate Minerals OXYGEN = oxidation. Occurs in Iron Minerals Carbon dioxide. Combines with water to form a weak CARBONIC acid and can dissolve Calcite Minerals Acid Precipitation. Released by human activities that make pollution.

RATE OF WEATHERING Climate: TEMPERATURE and PRECIPITATION have the greatest effect the rate of weathering. – Chemical Weathering occurs more in MARITIME TROPICAL (warm and MOIST) climates. More surface covered with plants and less icing – Mechanical Weathering occurs more in CONTINENTAL POLAR (cool and dry) climates. Cold slows down most chemical reactions

RATE OF WEATHERING Rock Types – Water-SOLUBLE minerals weather easily – Permeable Sedimentary rocks weather – Different layers weather at different rates

Other Factors More surface area = more weathering Topography (slopes, hills, etc) allows gravity to act on sediments

Erosion Transportation of Sediment

How Water Erodes

Soils Soil is the loose covering of broken rock particles and decaying organic matter over the top of the bedrock. Soil is made of – Rock particles and minerals (sand, silt, clay) – Humus is organic and provides PLANTS with air and water Soil Texture depends on particle SIZE

Soil Horizons The layers of soil with a soil profile (vertical sequence of soil) is called the soil horizon – TOP SOIL – Layer A: contains NUTRIENTS and minerals and is very dark – SUB-SOIL- Layer B: high in clay and is usually red or yellow in color – Layer C: Partially weather rock

Life in Soil Decomposers (such as fungi and bacteria) break down ORGANIC MATERIAL Animals mix SOIL LAYERS and allow air and water passage. Plants produce litter and then decay returning nutrients to the soil (humus).

Soil in the U.S. Polar (Alaska) – good drainage, no horizons, permafrost Temperate (Eastern and Central U.S.) – vary greatly – Grassland – fertile – Forest – less fertile Desert (Western U.S.) – high in salts and little organic material Tropical – can become infertile due to high rainfall

Soil Damage Loss of TOP SOIL Loss due to erosion – Desertification Climate Change, Overgrazing, Cutting down FORESTS Conservation – Contour plowing – CONSERVATION plowing – Fallow (allowing fields to rest) – CROP rotation

Karst Topography Groundwater contains some ACID – usually CARBONIC ACID – Carbon dioxide combines with Water – Acid dissolves some types of minerals (CALCITES - Limestones) and leaves others (QUARTZ – sandstones, igneous rocks, many metamorphic rocks). This differential erosion causes KARST TOPOGRAPHY.

Karst Topography

Features Caves Sinkholes Stalactites – from above Stalagmites – from below Disappearing rivers

Caves

Sink Holes

Stalactites

Stalagmites

Disappearing Rivers

Mass Movement by Gravity The downward movement of loose sediments and weathered rock. – Slide: moves as a block – Flow: mixing of particles – Fall: falling freely through the air.

Creep: slow, steady downhill flow of material

Slump: rotation and sliding on a curved surface

Mudflow: swiftly moving mixture of mud and water

Landslide: downhill movement of layer of topsoil

Avalanche: landslides with acculummation of snow

Mass Movement from Wind Mass movement from wind includes – Dust Storms – Dune Formation – Abrasion – Loes

Mass Movement by Glaciers A glacier is a large moving mass of ice. – Valley glacier: form in mountainous areas – Continental glaciers: cover large continent sized areas

The Water Cycle

Runoff Water moving along the surface will carry sediments. If surface is POROUS, then water can flow into the ground. – Plants slow erosion and allows more water into the ground – Light rains can allow more water into the ground – Soil types affect absorption

Watershed All the land that drains into a stream or river system is called the watershed. Suspension: particles carried in water Bed Load: particles pushed along by water in a stream

Streams Stream channel: the pathway carved by a stream Stream banks: the ground bordering the stream on either side Floods occur when streams or rivers rise over their banks. Flood plain: the broad flat area on either side of the stream banks. Meander: the bend and curves in a stream

Streams

Lakes and Freshwater Wetlands Lakes are depressions in the landscape that collect and hold water. Eutrophication: Excess nutrients cause algae blooms. The algae dies and decomposes, using all of the oxygen. Wetlands are land areas that are covered by water for part of the year. – Bogs – Marshes – Swamps

Groundwater and Infiltration Infiltration is when water on the surface flows into the ground An aquifer is permeable rock that may contain water.

Groundwater Zone of Saturation – the part of the aquifer that has water completely filling all the pores. – Upper boundary is the Water Table – Permeability – how easily water passes through Zone of Aeration – is the area above the water table – pores are filled with air.

Groundwater Systems Springs - Natural discharges of ground water where ground water is blocked by AQUICLUDES (Clay and Shale) Temperature is usually close to the regional average temperature – Hot springs usually form near residual igneous activity – Geysers are explosive hot springs that erupt at regular intervals.

Wells Holes that are drilled or dug into the ground to reach the aquifer – Drawdown – the difference between the water table level and the water level in the pumped well – Recharge – the water filtering into the well from the ground water Artesian well – a well in a CONFINED aquifer.

Data for Wells Worksheet SITESurface Elev. IN GREEN Water Table IN BLUE Aquiclude IN BROWN Pressure Surface IN RED 1396 m392 m388 m394 m