1708987
Description
Flashcards by Lucy Monger, updated more than 1 year ago
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Created by Lucy Monger
about 10 years ago
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| Question | Answer |
| Physical Weathering | Freeze thaw Salt Crystal Growth Pressure Release |
| Chemical Weathering | Hydrolysis Hydration Oxidation Carbonation Solution |
| Biological Weathering | Involves both Physical and Chemical weathering |
| Slides | Detached block remains large until the bottom of the slope where it is broken down on impact |
| Sheetwash | -The unchannelled flow of water over a soil surface -Divided into areas of high and low velocities |
| In Situ | Without any lateral movement (on the spot) |
| Pools | The deep part of the river located on the outer bend of a meander |
| Riffles | The ridges- often formed of gravel- found in the straight part of a river between two meanders |
| Cavitation | The explosion of air in joints and cracks as a result of air at very high pressure |
| Hydraulic Radius | Cross-sectional area of a river divided by the wetted perimeter |
| Wetted Perimeter | Total length of the bed and base of the river channel in contact with water in the river |
| Suspension | Smallest particles (silt/clay) carried in suspended load -important during times of flooding |
| Saltation | Large particles (sands/gravels) transported in a series of bounces as the salted load |
| Traction | Larger particles (pebbles) Shunted along the bed |
| Solution | In areas of calcareous (mostly or partly composed of calcium carbonate) rock, material carried in solution |
| Sediment Yield | The amount of material (debris) carried away by water |
| Entrainment | Picking up particles from the ground/ river bed |
| Unconsolidated Rocks | Loose, broken material that is often easily eroded |
| Consolidated Rocks | Solid rocks or sediment that have been bonded together by a sedimentary cement |
| What is a Pothole? How are Potholes formed? | -A pothole is a hole in the base of the stream of the river -Formed through abrasion by pebbles held up by turbulent flow in the eddies of the stream |
| What is an Eddy? | The swirling of a fluid and the reverse current created when the fluid flows past an obstacle |
| Why are Meanders formed? | When stream velocity has increased and the load is finer, in relatively straight channels, meanders develop as this is the only way the stream can use up the energy it now possesses equally throughout the channel reach |
| Thalweg | The line of maximum velocity in the river |
| Helicoidal Flow | A corkscrew-like motion that occurs in a meander |
| River Cliffs | The steep-sided slopes on the outer ben of a meander |
| Slip-off Slope | The gentle slope deposited on the inner bend of a meander |
| Bankfull Stage | Where the variables of the river (depth, width, velocity) of a river are unable to cope with additional water |
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Image:
delta (image/png)
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Delta |
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Image:
oxbow_lake (image/png)
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Oxbow Lake |
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Image:
braided_channel (image/png)
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Braided Channels |
| How is an Oxbow lake formed? | -Lateral erosion (caused by centfrifugal forces) is concentrated on the outer, deeper bank of the meander -During flooding erosion increases causing the river to break through and create a new steeper channel, the old meander is eventually closed off by deposition to form an oxbow lake |
| When do Braided channels occur? | -When the river separates into multiple small interlocking channels -Channel is now highly unstable and constantly changes form -Occurs when the river capacity can't transport its load in a single channel, be straight or meandering |
| What are Floodplains? | -Increased discharge due to heavy precipitation can lead to a bankfull stage -Channel variables become unable to cope and river spills out into surrounding areas -Repeated flooding leads to build up of alluvium and forms the floodplain -Also created by bluffs (steep banks or cliffs) |
| What are Levees? | -Raised ridges that run parallel to the edge of the channel and forms the repeated flooding of a river -Rivers flooding causes its velocity to drop as the floodwaters spill out -Heaviest and coarsest sediment are the first to be deposited and will build up over time |
| Alluvium | Fine sediment of silt and clay transported in suspension (very fertile) |
| Flocculation | The process in which clay and silt particles combine when fresh water mixes with the salt water |
| For Deltas to form a river needs to... | -Carry a large volume of sediment -Enter a still body of water (sea/lake) IF STRONG CURRENTS SEDIMENT WOULD BE CARRIED BY LONGHSHORE DRIFT |
| How are Deltas formed? | -Deposition increases if the water is salty; causes salt particles to group together and they become heavier -Vegetation increases the rate of deposition by slowing down the water -Coarser material deposited first and finest last |
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