Weathering, Erosion, Deposition
The breakdown of rocks at or near the Earth s Surface. Physical Chemical
- The breakdown of rock into smaller pieces without chemical change. - Dominant in moist /cold conditions - Creates more surface area
- Water gets into cracks, freezes and expands causing rock to split. - Occurs in climates with freezing and thawing temperatures EX: Pot-holes
- Roots grow into and under rocks - As roots grow they pry the rock apart
- Bumping and rubbing of rocks as they collide - Causes rocks to become smaller, smoother and rounder
- Surface rock peels off - Due to rock expanding and contracting from temperature and pressure changes
- The breakdown of rock through a change in mineral composition or chemical change. - Dominant in warm/moist climates - Occurs on the surface of rock materials
- When iron combines with oxygen to make iron oxide. What is iron oxide? RUST
- Carbonic acid in rain causes minerals to dissolve away. Ex: marble grave stones
- Water weakens the rock and the rock crumbles. Ex: feldspar become clay
- Weaker less resistant rocks weather away faster then harder more resistant rocks. - In diagram shale (layer A) is less resistant then the other rocks.
Factors that Effect Weathering Cold and Moist - Creates more surface area where weathering can occur - Longer exposure = more weathering - Weaker rocks are less resistant and weather faster
Factors that Effect Weathering Cold and Moist - Creates more surface area where weathering can occur - Longer exposure = more weathering Warm and Moist - Occurs on the surface where the rock is exposed to the atmosphere or hydrosphere. - Weaker rocks are less resistant and weather faster - Weakens the minerals in the rock so it breaks down easier.
Mineral Composition Examples: - Calcite in limestone and marble weather quickly because it dissolves in acidic water.
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- Soil is the result of weathering and biological activity over long periods of time
- Soil is the same substance as the underlying bedrock - Soil formed and stayed in the same place, this is rare - Soil is made up completely of different material then the underlying bedrock. - Soil was transported = moved
Weathering Leads to Soil Formation
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Erosion https://www.youtube.com/watch?v=kdx2kjvi51a http://www.polk.k12.ga.us/userfiles/898/classes/177311/weatheri ng%20webquest.pdf
The transportation of weathered rock materials. Streams (running water)
The transportation of weathered rock materials. Streams (running water) Glaciers (moving ice)
The transportation of weathered rock materials. Streams (running water) Glaciers (moving ice) Wave Action (waves)
The transportation of weathered rock materials. Streams (running water) Glaciers (moving ice) Wave Action (waves) Wind
The transportation of weathered rock materials. Streams (running water) Glaciers (moving ice) Wave Action (waves) Wind Mass Movement (gravity)
The transportation of weathered rock materials. Streams (running water) Glaciers (moving ice) Wave Action (waves) Wind Mass Movement (gravity) Gravity is the underlying force that causes all erosion
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- The most erosive agent Water Erosion - Gravity causes water to flow downhill - Sediments are weathered by abrasion - The faster the water moves the larger the particles it can transport - As water slows down the larger, rounder more dense particles settle out first - Sediments in stream move slower than the water - Streams have a V- shaped Valley
Any body of water with a current Streams, rivers, brooks, creeks, etc.
Oxbow Lake Slope The steeper the slope the faster the water flows The greater the volume the faster the water flows Volume of water flowing past a fixed point in a given period of time A cut off Meander - Curve in a stream - Outside of curve = water flows fastest, erosion occurs - Inside of curve = water flows slowest and deposition occurs
Stream Velocity
- Steep slope, straight channel - High energy, fast moving - Lots of erosion - Narrow V-shaped valley
- Gentler gradient, slower moving water - Meanders develop - Valley becomes wider than river channel - Flood plain develops (where water goes when river overflows)
- The land is almost flat - Levees form - along stream mounds of sediment are deposited when stream overflows - Oxbow lakes cut off meander
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Determined by the topography of the surface and the underlying bedrock - Most common - Looks like branches on a tree
- Occurs when stream flows away from a high point - Looks like spokes on a wheel
- Occurs on an eroded dome - Circular pattern with small tributaries going into each circle
- Occurs where drainage flows along folds and faults
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- All agents of erosion are driven by gravity - Examples of gravity erosion, are, landslides, dropping off cliffs, mass movement down steep slopes -After mass movement, rocks look rough and angular
Types of Mass Movement
Angle of Repose Angle of hill slope necessary for gravity to overcome friction and pull down sediment.
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Wave and Current Erosion
Wave Erosion - Wave action round sediments as a result of abrasion - Shores are protected by barrier islands
Beaches are formed by the weathering of continental and oceanic rocks - Ridge of sand formed along shore by the action of waves and currents. - Protect barrier islands from erosion
- A long narrow island running parallel with the main land made up of mostly sand. - Built by the action of waves currents and wind that distributes the sand. - Protects the main land from erosion
- Long Shore Current: the movement of sand parallel to the shore by waves. Sand moves in a zig-zag pattern.
-Beach protection structures that protect against long shore drift - Allows for eroded sand to be caught and pilled up.
Groins and Jetties affect Longshore Currents
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Glacial Erosion
- Large very slow moving mass of ice Glacier Erosion - Form in high latitudes and high elevations - Gravity causes a glacier to flow downhill - Push drag and carry any size sediment from boulders to clay - Deposition is unsorted (all mixed up, called Till) - Striation- parallel scratches and grooves in the bedrock - U shaped valley
Glacial Till: Unsorted Sediment
Striations
U shaped Valley
Glacier Movement A glacier is always moving, by either adding ice or snow or by melting and sublimation. If more ice and snow accumulates than melts glacier will ADVANCE If melting is greater than accumulation glacier will RETREAT
Define vocab terms using text book on page 19 and 20
Important Vocab: 1) Moraine
Important Vocab: 2) Drumlin
Important Vocab: 3) Kettle Hole
Important Vocab: 4) Outwash Plain
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Wind Erosion
Wind Right to Left
- Wind picks up and carries small sediment, the faster the wind blows the larger the sediment it can carry - Sandblasts rocks and creates cross bedded features - Wind deposits have a frosted pitted appearance
Cross Bedding
Sandblasted Rocks
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Deposition
Deposition As transporting agent slows down sediment begins to settle out. *Water and Wind deposits are sorted and layered. * Gravity and Glacial deposits are unsorted and not layered Rounder particles settle faster than flat particles Larger particles settle faster than smaller particles More dense particles settle faster than less dense particles
When larger, rounder and more dense particles settle out first in a distinct order. When sediments are dropped in not particular order (all mixed up)
Sediment Characteristics and Rate of Deposition
- Occurs when a stream enters a large body of water. - Velocity of stream slows down - Larger particles settle out first followed by smaller and smaller particles
Sorting of Sediments and Deposition Horizontal Sorting
- Sorting of sediments from bottom to top - Largest, roundest, and densest particles settle out first and are at the bottom Describe the relationship between setting rate and shape- - Faster water carries the bigger sediments, when slows down bigger sediments drop out first.
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Formation of Deltas - As a river flows into a larger body of water, it slows down and deposition occurs - When deposition is greater than erosion deltas form
- Area where water drains downhill into one large body of water -Includes all streams and land in the area Same as drainage basin
- Creek or stream that flows into a larger body of water
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