Agents+of+Erosion+(chapters+5-6)

=Unit 4: Agents of Erosion (Chapters 5 & 6)=

Essential Questions:

 * 1) How does porosity, permeability, aquitards, and aquifers influence groundwater?
 * 2) What conditions would create karst topography?
 * 3) What importance does deltas have?
 * 4) How can glaciation erode, alter, and reshape the surface of the earth?
 * 5) What type of wind erosional features can be seen in the Dust Bowl?

Recap

 * Weathering is the process that breaks up material at the earth's surface. This is done both chemically and mechanically. Mass Wasting events help to break up larger amounts of material and is due to the influence of gravity.
 * Erosion is the process by which wind, water, glaciers, and waves transport material from one location and carry it to another location.
 * Deposition is the process by which eroded material is deposited in a new location creating a new land feature.

Question of the Day: Why is running water a great importance to people?
=Running Water= >
 * Hydrological Cycle is the process by which freshwater is cycled through the environment. Steps to the hydrological cycle are evaporation (changing of liquid water into water vapor), transpiration (removal of water vapor via a medium like a plant leaf), condensation (changing of water vapor back to liquid water), precipitation (water falling as either snow, rain, sleet, or hail to the earth's surface), runoff (water moving across the earth's surface), groundwater (water filtering into the ground).
 * [[image:Watercyclesummary.jpg width="525" height="364"]]
 * Water filtration into the ground depends on
 * Intensity and duration of rainfall
 * Prior wetted condition of soil
 * Soil texture
 * Slope of the land
 * Nature of Vegetative cover
 * **Drainage Basin** is land area that contributes water to a stream/river.
 * **River Systems** have 3 parts to them: Zone of Erosion (at the head of the river, usually in higher elevation areas), Zone of Transport (in the middle of the river), and Zone of Deposition (at the mouth of the river, at lower elevation, close to sea level). Erosion, Transport, and Deposition takes place in all areas of a river/stream but these areas are predominantly where erosion, transport, and deposition take place.
 * **Streamflow** can be either laminar, all in one direction/uniform, or turbulent, in different directions/speeds/not uniform. Whitewater rapids are seen in streams/rivers where there is turbulent flow instead of laminar flow.
 * [[image:streamflow.jpg]]
 * **Stream Velocity** is depended upon
 * Gradient (rise/run) of the Stream. Elevation divided by the distance stream travels.The steeper the gradient, the more energy available for streamflow hence higher velocity and more erosion can take place.
 * Shape, size, and roughness of stream channel/bed. Deeper streams have more efficient flow because a smaller portion of the water is touching the stream channel/bed. Smooth channels/bed allows for more uniform flow whereas rough channels/beds cause for turbulent flow hence a slower velocity and less erosion.
 * [[image:streamvelocity.jpg]]
 * **Discharge** of a stream/river is the amount of water flowing pass a certain point in time. Usually measured in cubic meters per second or cubic feet per second. Discharge of a stream can be determined by multiplying the width of the stream by the depth of the stream by the velocity of the stream (w*d*v). Discharge of streams isn't constant because of the seasonal variation in precipitation.
 * Practice Problem: What is the discharge for a stream that is 10000m in width, 500m in depth, and has a velocity of 25.5 m/s?
 * Discharge= w*d*v
 * Discharge= 10000m * 500m * 25.5m/s
 * Discharge =127,500,000 cubic meters per second (m 3 /s)
 * Streams/Rivers can transport material in several ways.
 * Dissolved Load is the material carried by a river that is in solution (ie: is dissolved by the water).
 * Suspended Load is fine sediment material that is carried by the flowing body of water.
 * Bed Load is the sediment that is carried along the bottom of the stream channel/bed. This material can be rolled, bounded, or slid across the bottom of the stream channel/bed.
 * Streams can vary in their ability to carry their load. Their ability to carry a load is based upon
 * Competence: maximum size of particles it is able to transport. This is based upon the stream's velocity. For example, if the stream's velocity doubles, its competence increases 4x.
 * Capacity is the maximum load a stream can carry. This is directly related to the stream's discharge. The more volume of water flowing in a stream, the greater is its capacity to haul material.
 * Stream Channels/Beds confine the flow of the river/stream.
 * Bedrock channels are channels in which the river is cutting directly into solid rock.These channels are usually winding and curving instead of a straight channel and usually whitewater rapids can be found along the channel.
 * Alluvial channels are channels in which there is unconsolidated material found along the bed and banks of the channels.Meandering channels are channels in which there are loops/bends in the river. Cut banks are found along the side of the river in which erosion is taking place. This is usually the outside of the bend. Point bars are where there is a slower velocity so there is deposition taking place and are found inside of the bend. Usually a meander can be cutoff due to a collection of deposited debris forming a U-shaped lake called an Oxbow lake.
 * [[image:TGA115t.jpg width="500" height="388"]]
 * Streams can only erode their channels until they reach base level. This is the lowest elevation a stream can erode its channel to. Streams well above base level will cut downward into the rock strata causing V-shaped valleys with rapids and waterfalls.
 * **Erosional and Depositional Features created due to running water.**
 * Floodplains are broad, flat areas along the side of a river/stream created when the river overflows its banks. Material is deposited in the area making these areas rich in sediments.
 * Meanders are loops/bends in a river as the river cuts into the bedrock.
 * Bars are channel deposits often composed up of sand or gravel.
 * Deltas result when a stream/river dumps into a larger body of water (ie: ocean) and material settles out.
 * Natural Levees run parallel to a river channel along its banks and forms when the river overflows it banks.
 * Backswamps result where there is area of poorly drained water resulting in the formation of natural levees.
 * Yazoo tributaries are rivers that run parallel to the major river but can't join the major river because levees block it.
 * Alluvial fans form when a river/stream comes in contact with flat land causing material to spread out at the mouth of the river.[[image:whs-earthscience/TGA109t.jpg width="575" height="441"]]
 * Drainage patterns seen can be dendritic (branched like a tree or leave veins), radial (comes from a central location like a volcano), rectangular (right-angles due to bedrock cracks/faults), and trellis (tributaries running perpendicular to the major river).
 * [[image:TGA119t.jpg width="500" height="388"]]

Groundwater
> == == ==
 * Most important and widely available resource.
 * Largest reservoir of freshwater
 * Used by over 50% of the population for drinking water, 40% for irrigation and 25% for industrial needs like hydroelectric power.
 * Overuse has caused problems with streamflow depletion, land subsidence, and increased pumping costs.
 * Contamination of groundwater due to human activity and is an increase threat.
 * [[image:TGA140t.jpg width="500" height="388"]]
 * Important erosional agent by dissolving soluble rock, forming surface depressions (sinkholes), equalizer of streamflow, sustains streams during dry periods, forms Karst topography and geysers.
 * ==[[image:whs-earthscience/TGA132t.jpg width="500" height="388"]]==
 * Rate of movement and amount of ground water depends on
 * Porosity-amount of pore spaces in the sediment/rock
 * Permeability-ability for material to transmit water.
 * Aquitards- impermeable layers of material that prevents water flow (ie: clay)
 * Aquifers-permeable layers of material that transmits water freely (ie: sand, silt)
 * [[image:TGA126t.jpg width="650" height="491"]]



== =Glaciation=
 * Accumulation, Compaction, and Recrystallization of snow over 100s to 1000s of years.
 * Two types of glaciers
 * Continental Glaciers: Also known as sheet glaciers. These are the glaciers associated with ice ages. Glacier is thicker in the middle or dome area due to accumulation of snow and ice and moves in all directions. They are very wide and cover land/continents.
 * Alpine Glaciers: Also known as valley glaciers. These are glaciers that are found in mountainous regions along the mountain valley. They are not wide due to the walls of the valley but are long.
 * Other types of glaciers are ice caps and piedmont glaciers.
 * Glacial Movement
 * Movement by glaciers is slow and can be done by flowing across the land or slipping along the ground.The middle of the glacier moves faster than the sides because the sides are influenced by friction. Friction also causes the bottom of the glacier to move slower than the middle/top of the glacier. This can cause crevasses.
 * [[image:TGA149t.jpg width="640" height="480"]]
 * Within a glacier there are different types of zones: fracture, wastage, accumulation.
 * Zone of accumulation is where there is more snow and ice forming allowing for the glacier to advance forward.
 * Zone of wastage is where there is melting of snow and ice which causes the glacier to retreat.
 * Zone of fracture is where there are crevasses due to the slower movement of the glacier at the bottom than at the top.
 * If there is more accumulation than wastage, glacier advances. If there is less accumulation than wastage, glacier retreats. If accumulation equals wastage then the glacier has no net movement.
 * [[image:TGA151t.jpg width="640" height="479"]]
 * Glaciers erode by plucking and abrasion of material as the ice moves over the land. Plucking happens when meltwater from the glacier penetrates cracks in the rocks and freezes (Frost wedging) and the force of the glacier pries up material as it continues to move. Abrasion happens when the material carried by the glacier wears away at other rocks as the glacier moves over it. Rock flour and Striations are created when abrasion happens. Rock flour is pulverized rock that is carried by a meltwater stream. Striations are long scratches or grooves in the surface of the rock.
 * [[image:TGA156t.jpg width="560" height="420"]]
 * Alpine Glacier Erosional Features.
 * As a glacier moves through the valley, it will erode the material it comes in contact with forming and reshaping the valley regions.
 * Glacial Troughs- widen and deepened u-shaped valleys that were originally v-shaped before the glacier
 * Hanging Valleys-large valleys that enter a glacial trough. Can have waterfalls.
 * Cirques-bowl-shaped structure at the head of a glacier
 * Aretes- Sharp-edge ridges between valley glaciers
 * Horns-Sharp-pyramid like peaks created due to several glaciers
 * Tarn- small lake in a cirque
 * Fjords- deep steep sided inlets where the sea meets a glacial trough
 * Pater Noster Lakes- lakes within a glacial trough
 * [[image:TGA155t.jpg width="560" height="420"]]
 * Glacial Depositional Features
 * Glacial debris can be called till (unconsolidated material) or drift (consolidated material). This debris is deposited as the glacier retreats.
 * Glacial erratics- boulders found that have a different bedrock than the soil composition below.
 * Moraines-ridges of till that can form: along the side of a glacier (lateral moraine), when two glaciers meet (medial moraine), when the glacier first retreats (end/terminal moraine), after a terminal moraine (recessional moraine) or when the ice front recedes slowly (ground moraine).
 * Outwash Plains- accumulation of drift located along the end moraines created by meltwater streams
 * Drumlins- asymmetrical hills of till that are shaped as the glacier recedes.
 * Eskers-deposits of sand and gravel made by meltwater streams flowing in tunnels beneath the ice.
 * Kames-steep-sided hills formed when till was deposited in depressions.
 * Kettle Lakes/Ponds- melted ice underneath till
 * [[image:TGA159t.jpg width="720" height="539"]]
 * Glaciation caused by
 * Plate tectonics
 * Change in the Earth's orbit
 * Change in the amount of energy given off by the sun
 * Albedo (reflection of light from a surface) and Atmospheric conditions

Wind

 * Mechanical weathering is the main process that alters and shapes arid regions.
 * [[image:TGA170t.jpg width="568" height="376"]]
 * Running water erosion is infrequent in a dessert but does the most erosional work when available.
 * Wind can carry fine particles in suspension while it can move heavier particles by bouncing, rolling, sliding along with surface; similar to the bedload of a river.
 * Compared to running water, wind erosion is less significant erosional agent.
 * Erosion happens by deflation (lifting and removal of loose material) and by abrasion. Deflation can form blowouts (shallow depressions) and desert pavement (removal of sand and silt and leaving of coarser particles)
 * [[image:TGA175t.jpg width="560" height="420"]]
 * [[image:TGA176t.jpg width="560" height="420"]]
 * Depositional features created by wind are loess (deposits of silt) and dunes (mounds and ridges of sand).
 * [[image:loess6.jpeg width="366" height="245"]]
 * [[image:loess2.jpg width="300" height="278"]]
 * Dunes have a crest (topmost part), a slip face (steeper front) and cross beds.
 * [[image:TGA177t.jpg width="560" height="420"]]
 * Types of Sand Dunes
 * [[image:TGA178t.jpg width="400" height="300"]]
 * [[image:TGA179t.jpg width="560" height="420"]]
 * [[image:TGA180t.jpg width="560" height="420"]]
 * [[image:TGA181t.jpg width="560" height="420"]]
 * [[image:TGA182t.jpg width="560" height="420"]]
 * [[image:TGA183t.jpg width="560" height="420"]]