surface processes & landscapes unit 9 topics 9, 10 & 14 in your review book
TRANSCRIPT
Surface Processes & Landscapes
Unit 9Topics 9, 10 & 14 in your review book
I. WEATHERING
Weathering is the chemical and physical alterations of earth materials at or near the earth’s surface
A. Types of Weathering1. Physical Weathering
The mechanical breakdown of earth materials (rocks) at or near the earth’s surface.Changing the size/shape of the material.
Physical weathering does NOT change the characteristic properties of the material.Each time a material is made smaller, its surface area increases.
size es surface area
THANKS MOLLY
2. Chemical Weathering
The process by which chemicals such as oxygen, acids and water break down rocks and other earth materials.
Chemical weathering does change the characteristic properties of the material…new materials are created!
B. Agents of Weathering1. Wind: weathering is due
to the material carried by the wind (such as sand)
2. Water3. Temperature change4. Animals and Plants
C. Specific Types of Weathering1. Ice wedging/Frost Action:
Physical weathering occurs when the water contained within the material freezes, expands, melts and evaporates
Frost action requires moisture and temperatures ranging from above to below freezing
2. AbrasionPhysical weathering that occurs when different substances move against one another creating friction which results in sediment that is round and smooth.
3. Plant Action
Physical weathering that occurs when the roots of plants grow and enlarge breaking rocks apart.
4. Oxidation
Chemical weathering due to a reaction between the material and oxygenExample: rust
5. Acid RainChemical weathering caused by the gaseous by-products of industry that dissolve in rain water making it acidicMarble and limestone are most affected by acid rain.
6. HydrolysisChemical weathering that occurs when water reacts with the material.Usually some or all of the material is dissolved in the water.
D. Factors that influence the Rate of Weathering1. Temperature:
Most influences chemical weatheringChemical weathering occurs faster at high temperatures
As Temperature increases,Rate of chemical weathering increasesGraph:
As Temperature increases,Time for chemical weatheringdecreasesGraph:
2. Moisture
Most influences the rate of chemical weatheringChemical weathering occurs faster with more moisture
As the amount of moisture increases,The rate of c. weatheringincreasesand the time for c. weatheringdecreasesGraphs:
CHEMICAL WEATHERING OCCURS BEST IN HOT, MOIST (HUMID) CLIMATES
3. Size
Weathering of all types occurs faster as size decreases
As size decreases, surface area increases
Therefore, more of the material is exposed to the agents of weatheringallowing weathering to occur faster.
Decrease size:Increase surface area:increases rate of weatheringDecreases time for weatheringGraphs:
Increase size:Increases time for weathering
Increase surface area:Decreases time for weatheringGraphs:
4. Composition
Rate of weathering can be influenced by the mineral content of the rock.
A rock composed of minerals with a high hardness will be more resistant to weathering than one made up of “softer” mineralsAs resistance increases:Rate of weathering decreasesTime for weathering increasesGraphs:
5. Topography Rock structure can influence rate of weathering.Steep slopes may be more prone to physical weathering than grassy, gentle slopes
As slope increasesRate of weathering increasesTime for weathering decreasesGraphs:
6. Vegetation
As the amount of vegetation increasesThe rate of weatheringDecreasesThe time for weatheringincreases
E. Products of WeatheringSediments result from the weathering of earth materials
Biological activities add organic material (humus) to sediment creating soil
1. Soil Profile
A side view of the horizontal layers of soil.These horizontal layers are called soil horizons
Biological activity creates organic materialZone A: also called topsoilContains the most organic material and is most fertile
Zone B: also called subsoilContains a mixture of sediment and humusIs slightly fertile
Zone C: Contains sedimentIs infertileBedrock:The layer of impermeable rock which is weathered to create sediment
Infiltration: to soak into…the movement of water down through soil layers.Leaching: to bring organic material down through soil layers as water infiltrates
2. Types of Soila. Residual soil: soil that stays
soil that remains on top of the bedrock of origin (parent bedrock)The composition of residual soil is similar to the bedrock beneath it
b. Transported SoilSoil that goesSoil that has been moved from its location of origin.The composition of transported soil differs from that of the bedrock beneath it
Residual soils tend to be thicker and more well developed than transported soilsMuch of the soil in NYS has been transported by the glaciers that passed through
II. EROSION
The movement of earth materials
The driving force of erosion isgravity
A. Mass MovementThe movement of earth materials by gravity alone
1. Landslides, mudslides, avalanches: large quantities of material moving rapidly down hill.
2. Slumping
occurs when the material slides along a curved surface
3. Hillside creep:a slow, imperceptible downslope movement of soil
Talus is the result of mass movement near steep slopesIt is a pile of rock fragments at the base of a cliff
Landslide
Mudslide
Slumping
Hillside Creep
Talus
B. Agents of Erosion1. Wind2. Water: • running water is the
dominant agent of erosion!
3. Glaciers
C. New TermSTRICKStands for:StreamRiverCreekIt will be used to refer to any moving body of water
D. Factors influencing rates/amount of erosion
1. VelocityAs the velocity of the agent of erosion increases,the amount of erosion increases
a. Factors influencing velocity
1. Slope• As slope increases• Velocity increases• Therefore, erosion
increases
2. QuantityDischarge is the amount of water flowing past a certain point (volume)As discharge increases,Velocity increasesTherefore, erosion increases
Discharge is greatest
tributary
Rainstorms and meltwater can increase dischargeWhen ppt > infiltration (it rains faster than it can soak in), runoff occurs and discharge increasesHuman activities such as dams, and development can also affect discharge
3. Shape of the Strick Bed
In a cross-sectional view, water flows fastest through the center
*
Surface tension between the air and the water molecules slows the water at the surfaceFriction between the water molecules and the strick bed slows the water along the sides and bottom
Direction of flow
Slowed due to friction along the sidesFastest at the middle of the leading edge
In a bird’s eye view:
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•Through the course of a strick
Water flows fastest near the source and along the outside of a curveWater flows slowest near the mouth and along the inside of a curve
Slow alongthe inside
Fast along the outside
Fast near the source
Slow near the mouth
4. AgeThe older a strick is, the wider it is, and the more it meanders (curves).Generally, as age increases, discharge decreases, and slope decreases…which decreases velocity and erosion
E. Carrying Capacity
The amount and size of sediment able to be transported by a strickis dependent upon the velocity of the strick.As velocity increases, transportable size increases
The material carried travels slower than the strick.The velocity needed to initiate erosion is greater than the velocity needed to maintain erosion.See ESRT page 6 for velocity and carrying capacities.
The stream can carry everything at and below the line
F. Methods of Transportation
1. Large particles are carried by bouncing and rolling along the bottom: in traction
2. Small particles are carried in suspension: in the middle (colloids)
3. Low density particles float on the surface
4. Soluble materials are carried dissolved in the water: in solution
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III. DEPOSITION
The release of sediments from the agent of erosion
AKA: sedimentation
A. Factors Influencing amount of deposition
1. Velocity of the agent of erosion:As velocity increases,the amount of deposition decreases
B. Factors influencing the rate of settling
1. Particle size: Large particles are deposited fasterLarge particles settle out firstWhen size increases,settling rate increases andsettling time decreases
2. Particle densityMore dense particles settle out first and fastest.When density increases, settling rate increases andsettling time decreases
3. Particle shapeRound particles settle out first and fastest.When roundness increases,settling rate increases andsettling time decreases
C. Location of deposition
1. At the mouth:Where the strick meets the larger body of water, velocity decreases and deposition increases
2. At the inside of a curveVelocity is slower along the inside of a curve,therefore, deposition is dominant
3. When the slope of the strick decreases, velocity decreases and deposition increases.
4. Older stricks experience more deposition than younger stricks
5. Deposition occurs more along the side banks of a strick …
• downcutting creates the characteristic V-shaped valley of a strick
D. Results of Deposition
1. In still water:Vertical sorting occursThis results in beds of sediment sorted according to size
Repeated depositional events result in graded beds … separate layers of sorted sediment
2. In moving water
Horizontal sorting occurs as velocity decreases in a strick
Resulting in a gradual decrease in particle size as the strick gets closer to the mouth
A delta forms at the mouth of a strick due to the rapid slowing of the strick as it enters the still water of a placean (pond, lake, ocean)This is a triangular shaped deposit of fine grained sediments
Memorizable:Deposits by water are:
sortedand the sediments aresmooth and round
Stream Valleys are V-shaped!
E. Deposition by glaciersand resulting landforms
Glacial deposits are unsortedSediments in glacial deposits are: angular and scratched (striations)Glacial valleys are U-shaped and the bedrock is striated
Unique features created by glaciers1. Moraines: irregular hills of
unsorted sediment created along the sides: lateral moraineand leading edge: terminal moraineand as it melts: recessional moraine
2. Erratic: a large boulder deposited by the glacier
3. Kettle: a round depression created when a buried block of glacial ice melts
4. Kettle lake: created when a kettle fills with water
5. Transported soil: soil relocated by a glacier … has unsorted sediments and a relatively thin A-layer
6. Esker: a long, winding ridge of layered sediment deposited by a stream flowing under a melting glacier
7. Drumlin: a long, smooth, canoe-shaped hill of till formed when a glacier moves over an older moraine. The steeper slope of a drumlin faces the direction the glacier came from.
8. Outwash: sediment deposited by the meltwater of a glacier. It contains gravel, sand, and fine silt.
9. Outwash plain: the area at the leading edge of the glacier where the meltwater streams flow and deposit outwash.
Memorizable:Glacial deposits areunsortedangularscratchedGlacial valleys areU-shaped!
F. Deposition by WindWind sorts sediment by sizeWind transports/deposits sand-sized sediments Wind blows sand into hills of sand called dunes
Wind blows particles of sand up the windward sidedepositing them on the downwind side
WIND
EEKS
G. Coastal Deposition
Sandbars are formed when waves advance and retreatcreating low ridges of sediment parallel to the shore
If a sandbar becomes connected to the beach, extending into deep water and rising above sea levelit becomes a barrier islandA lagoon is the section of the ocean between the beach and the barrier island
A peninsula is an area of land almost completely surrounded by water…connected to the mainland by an isthmus (a narrow portion of land connecting the peninsula to the mainland)
H. Erosional-depositional system
A system in which the amount of erosion is equal to the amount of deposition
Resulting in a
Dynamic equilibrium!
1. Energy of strick flowKinetic energy: energy of motion
Potential energy: energy due to position (stored energy)
As a strick flows from source to mouth:PE is highest at the source,and is converted to KE as the strick moves downslopeand is converted back to PE at the mouth
source
mouth
High PE Low KE
Changes to KE:
PE decreases
KE increases High PE Low KE
The PE at the mouth is less than the PE at the sourceEnergy is transformed by friction into heat and sound.
When KE is high, erosion is dominantWhen PE is high (KE is low), deposition is dominant
I. Erosional-Depositional features
1. The outside of a curve is faster; erosion is dominant; depth is greater
2. The inside of a curve is slower; deposition is dominant; depth is less
A B
A B
3. Oxbow lakes are created when a meander in a stream becomes cut off.
** see illustration!