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Gr10 Earth Sci Reg
9.2 EROSION VERSION 2
| Question | Answer |
|---|---|
| erosion | When rocks are weathered and produce particles that are TRANSPORTED as SEDIMENTS. weathered rocks that are transported as sediments |
| what causes erosion? | GRAVITY is the main force behind erosion. Insolation is an INDIRECT cause. The sun's energy drives the water cycle: 1) it produces precipitation, running water, glaciers and 2) it drives wind patterns that create ocean currents and waves. |
| insolation | Exposure to the sun's rays. |
| mass movement | When rocks and sediments are pulled downhill by gravity (landslide / direct gravity erosion). |
| Direct Gravity Erosion | Mass movement. It involves two OPPOSING FORCES: 1) the downward pull of GRAVITY and 2) FRICTION (attempts to keep objects in place). |
| running water | The MOST COMMON natural agent of EROSION on Earth's surface. |
| stream | When running water erosion is confined to a CHANNEL. |
| tributary | A smaller stream that FLOWS into a larger stream. |
| stream abrasion | When large solid sediments are carried by ROLLING or BOUNCING along a stream bottom. The result is ROUNDED sediments. |
| V-shaped valley | The SHAPE formed by a stream over time due to stream downcutting, runoff and mass movement. Causes the sides of the valley to CAVE IN. |
| downcutting | When a stream/river carves out a canyon or valley, cutting down into the earth and eroding away rock. |
| watershed | An area of land drained by any one stream; the DRAINAGE AREA. |
| divide | A region of higher land that separates one watershed from another. |
| stream velocity | How FAST a stream flows - 3 factors: 1) GRADIENT (SLOPE of the stream), 2) DISCHARGE (volume of water in a stream), and 3) STREAM CHANNEL SHAPE (the shape of the bed of rock or loose materials that confine a stream. |
| stream velocity impact | As SLOPE or DISCHARGE increases, velocity INCREASES. |
| stream channel shape | The shape of the bed of rock or loose material that confines a stream. |
| velocity of wide & flat stream channel | Large surface in contact with moving water, therefore a large amount of friction. The LARGER the amount of friction, the SLOWER the stream velocity. |
| velocity of semicircular stream channel | Smaller surface in contact with moving water, therefore less friction. The SMALLER the amount of friction, the FASTER the stream velocity. |
| velocity within a stream | Straight stream channel - maximum velocity at center of stream Curved stream channel - max velocity at outside of the curve. |
| velocity and depth | Greatest velocity (FAST) - just below the surface. Lowest velocity (SLOW) - at the stream bed or bottom of channel. FRICTION slows velocity at 1) air-water surface and 2) stream bed |
| stream velocity & sediments | Solid sediments move slower than the stream. The GREATER the stream velocity, the stream can carry LARGER sediment particles that and MORE sediment particles. |
| evolution of stream | Streams change over time when there are changes in 1) ELEVATION, 2) GRADIENT, 3) VOLUME of water, 4) available SEDIMENTS. |
| EARLY stage of a stream | The stream's energy is used to downcut a narrow V-shaped valley. It has a steep slope, abrupt changes in elevation, and waterfalls and rapids. DOWNSTREAM - water from tributaries and ground water INCREASE the size of stream. |
| MIDDLE stage of a stream | The stream is larger and it shifts course in a series of bends and turns (MEANDERS). Stream carries into a wider valley. During flooding, steam flows out into valley and deposits sediments (FLOOD PLAIN). |
| END stage of a stream | The mouth of stream: DISCHARGE is LARGE, but GRADIENT/SLOPE is LOW/SMALL. The valley and flood plain are WIDE. There is frequent FLOODING and sediment DEPOSITS (LEVEES). At very end is DELTA. |
| finger lake | Body of water in U-shaped valleys that were carved by glaciers |
| meanders | bends or turns in a stream |
| flood plain | Formed by a stream flowing into a WIDE valley and depositing SEDIMENTS. |
| delta | Land formed from sediments deposited over time from the shifting channel at the mouth of stream. FAN shaped. |
| Wind Erosion | Caused by loose sediments that impact solid surfaces. Found in: 1) deserts and 2) by lake and ocean coastlines. Two aspects: DEFLATION (wind blows away loose sediments, lowering land surface) and SANDBLASTING (abrasion). |
| sandblasting | When wind blows sediments against rocks or large objects. the Wind can lift sand grain about one meter in the air, so lower portions are more eroded than upper portions. |
| glacier | A naturally formed mass of ice and snow; it moves downhill on land due to gravity. |
| glacial movement | When a glacier moves over land, loose rocks and materials beneath it freeze into the ice and are dragged along. Glacial ice acts like a fluid; its motions are like those of a stream. "RIVER OF ICE". |
| glacial grooves | Gouging and sanding actions on rock surfaces caused by the movement of a glacier. |
| glacial parallel scratches | Scratches on bedrock that show the direction that a former glacier moved. |
| U-shaped valley | When the wide, thick ice of a glacier erodes a valley's walls and the rock beneath; a valley carved from glaciers. |
| Where does wave and current erosion happen? | Happens when lake or ocean waters meet land |
| breaking waves (surf) | When waves enter shallow water near the shore they drag against the bottom. The waves become unstable and water rushes towards the shore. |
| sandbar | Sediments deposited in a series of mounds in the zone of breaking waves. |
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