Weathering Weathering Physical mechanical weathering The process by
Weathering
� Weathering � � Physical (mechanical) weathering � � The process by which rock is broken down into smaller pieces Chemical weathering � � The breakdown of rock material by physical and chemical processes The breakdown of rocks by chemical reactions Abrasion � The breaking down and wearing away of rock material by the mechanical action of other rocks Rocks rubbing/grinding together � Oxidation � � The process by which other chemicals combine with oxygen Acid precipitation � When acids fall to earth like rain
Weathering MECHANICAL (PHYSICAL) � Rock is broken down into smaller pieces Temperature changes � Pressure changes � Plant and animal actions � Water, wind, and gravity � CHEMICAL � Breakdown of rocks by chemical reactions Oxygen in the air � Acids �
Mechanical (Physical) Weathering � Temperature Change � Changes in temperature can cause rocks to break apart (more prominent if water is present) � Ice wedging- causes cracks in rocks to expand break apart When water collects in cracks of rocks, it freezes and expands, breaking apart the rocks
Mechanical (Physical) Weathering � Pressure change � Rocks form under pressure in Earth’s crust � Rocks are exposed and break away, decreasing the pressure Rock expands and outer layers slowly peel away due to pressure changes �Exfoliation ^
Mechanical (Physical) Weathering � Animal Action � Digging burrows allows rock to be exposed Squirrels, prairie dogs, ants, earthworms � Wind, Water, Gravity � Abrasion occurs when rocks wear down other rocks � Wind, water, and gravity cause weathering by abrasion Landslide (gravity) Sandstorms (wind) Rocks tumble in rivers (water)
Mechanical (Physical) Weathering � Plant Growth � Roots of plants start small � They grow inside cracks of rocks and get bigger causing the rocks to break apart
Chemical Weathering � Chemical weathering- breakdown of rocks by chemical reactions � Agents of chemical weathering: Oxygen in the air Acids
Reactions of Oxygen � Oxygen reacts with different compounds in rocks � Rock surfaces change color Especially rocks containing iron
Reactions with Acid Precipitation � Acids in the air form when chemicals combine with water � EX: burning fossil fuels � Acid precipitation Causes rocks to break down and change composition
Acids in Groundwater � Acids in groundwater can cause rocks to dissolve �A small crack can become an extensive cave system � Dissolved rock is later deposited Stalactites stalagmites
Reactions with Acids in Living Things � Acids are produced naturally by living organisms � EX: Lichens that live on rocks and trees produce a weak acid Weakens and breaks down rocks
Erosion and Deposition by Water
Erosion and Deposition � Erosion � � Deposition � � � Fan-shaped deposit that forms on dry land An area of shoreline that is made up of material deposited by waves and currents Sandbar � � The place where land a body of water meet Beach � � Water located within the rocks below earth’s surface Shoreline � Streams deposit their loads in the fan-shaped delta Alluvial fan Ground water � Layers of deposited sediment form this flat area Delta � � The process by which eroded material is dropped Floodplain � � The process by which sediment and other materials are moved from one place to another � An underwater of exposed ridge of sand, gravel, or shell material Barrier Island � Long, narrow island, usually made of sand, that forms parallel to the shoreline a shore distance offshore
Erosion and Deposition EROSION � � � The process by which sediment and other materials are moved from one place to another Erosion takes place by way of rivers, streams, rain, wind… Over time, erosion causes streams to widen and deepen DEPOSITION � � Once erosion takes place, sediment is picked up and will be dropped off somewhere Deposition- the process by which eroded material is dropped Occurs when gravity’s downward pull is greater than what is carrying the sediment � Takes place when water or wind slows down � A stream may deposit materials along is bed, banks, and mouth which forms new landforms �
A Stream’s Ability to Erode � Gradient � � The measure of the change in elevation over a certain distance Steepness of a slope Water with a higher gradient moves faster � Load � Materials carried by a stream � Streams with a larger load has a high erosion rate Discharge � The amount of water that a stream carries in a given amount of time Increases when a major storm occurs or snow melts As it increases, its erosive energy , speed, and load increase
Compare and Contrast Erosion and Deposition
Run of a River � Landforms a stream creates � Canyons and valleys 6 million years ago, the Grand Canyon was flat. The Colorado River eroded the rock and formed the Grand Canyon over millions of years Flowing water can cut through rock and form steep canyons and valleys
Run of a River � Floodplains by deposition When a stream floods, a layer of sediment is deposited over time. � Sediment contains nutrients…very fertile � The channel (river or creek) may run straight or may curve (meanders) � Moving water erodes the OUTSIDE banks while depositing sediment on the INSIDE banks � • Deltas and Alluvial Fans by Deposition • When channels empty into a larger body of water, it deposits load • Form of a delta – fanshaped pattern • Form of an alluvial fan – fan-shaped deposit that forms on dry land
More Water Works � The movement of water underground causes erosion � � Slightly acidic groundwater can cause erosion can dissolve rock � � How most caves are formed Deposition � � Groundwater Stalagmites and stalactites When roof of cave is no longer supported by water, sinkholes form
Recap � � � Name one similarity and one difference between alluvial fans and deltas The Grand Canyon was caused by… How are erosion and deposition involved in groundwater?
Surf vs Turf � The rate at which rock erodes depends on the hardness of the rock and the energy of the waves � � � Storms Shoreline features that are created by erosion � � � Sea stacks Sea arches Sea caves Headlands Wave-cut platforms � � Sea Cliff-forms when waves erode and undercut rock to make steep slopes Wave-cut platform- what’s left after a sea cliff erodes beneath the water line Headlands- formed as some parts of a cliff are cut back faster than other parts Sea caves- waves cut deep into cracks and form large holes Sea arch- cave that is eroded to the other side Sea stack- sea arch collapses
Sea Formations
Shifting Sands � � Waves and currents carry a variety of materials: sand, rock, dead coral, and shells Beach- area of shoreline that is made up of material deposited by waves and currents � � Not all beaches are made of sand Deposited material can also form sandbars and barrier islands.
Coastal Landforms Barrier Island Sandbar
Pg 39 � � � Read with a partner On your own, write step-by-step instructions on how a barrier island is formed Share with your partner
Erosion and Depostition by Wind, Ice, and Gravity Lesson 4
Abrasion
Deflation
Dunes
What kinds of Ice shape Earth � Glaciers mass of moving ice that forms by the compacting of snow by natural forces � Found anywhere on land where it is cold enough � Steeper the slope, the faster it moves � � Large � � Glacial drift- general term for all of the materials carried and deposited by a glacier Alpine- glacier moving in a mountainous area Continental glacierthick sheets of ice that may spread over large continental areas
Alpine Glacial Formations Horn Cirque U-Shaped Valley Arête
Glacial formations Erratic: large boulder transported and deposited by a glacier Kettle lake: form when massive chunks of ice are buried by glacial drift The ice melts and forms a lake
Gravity’s effect on Earth � Mass movement- the shifting of materials (rocks and soil) downslope � Slow mass movement Creep- extremely slow movement of materials downslope � Rapid mass movement More dangerous, often takes place on steeper slopes. Rockfall- loose rocks fall down a steep slope Landslide- sudden movement of a large amount of material downslope Mudflow- rapid mass movement of mud �lahar
Soil Formation
What causes soil to form? � Soil: loose mixture of small rock fragments, organic matter, water, and air � Steps in soil formation 1) Weathering of parent rock a) Breaks down rock into tinier pieces b) Mixes in with organic matter 2) Decomposition and mixing by living things a) Decomposers break down dead plants and animals 1. Fungi, bacteria b) Decayed organic matter: humus 1. found in top layer of soil 2. Humus is mixed in by animals a) Earthworms, gophers
How long it takes for soil to form… A. Four main factors determine how long it takes soil to form Rock type (parent material): rate of weathering depends on the structure of the rock 2. Climate: soil develops quicker in warm, wet areas 3. Topography: Soil is formed quicker on steeper slopes than on flat land 4. Plants and Animals: soil develops slower without plants and animals 1.
What are some properties of soil? � Soil texture, color, chemistry, pore space, and fertility
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