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The life of a river
Global
| Question | Answer |
|---|---|
| Where does a river start | From the mountaintops |
| 3 stages of a river | Upper, middle and lower |
| upper section | begins at the source of the river, the rainwatwer trickles in between seand, gravel and fractures in rock. They dischrge into a stream and form tiny rivers called rivulets. the rivulets grow larger and become streams ,or they flow into streams and add to |
| charcteristics of the upper section | Deep narrow valley, interlocking spurs fast flowing river (erosion is predominant) pot holes on river bed rapids and water falls. |
| Rapids | stretches of fast flowing water going over a rocky shallow riverbed. different resistance amoung rocks causes them. formed when the hoh goes from hard rocks that resists the erosions to the soft rock that erodes more easily |
| waterfalls | occur when a band of hard rocks lies across the river w softer rock downstream. at first they are rapids but as the soft rock erodes they become |
| speed of a river | the gradient when flowing down a steep slope goes faster than one going dowm a gentle descent. material such as rocks also affect. rocks hat protrude out can slow the water bc of friction |
| attrition | collision of rock fragments in the water against one another. particles are broken into smaller pieces and becme smoother |
| Solution | Corrosion. process by wchich the reacts chemically with soluble materials in the rocks and dissolves them. Hydrauloc action is when the rocks are forced away from the bank. when the water enters small cracks the pressure breaks the rocks into smaller piec |
| Glacial Valleys | regions that were one formed by glaciers. as they slowly moved down the mountins they created a u shaped valley. the same type of erosion takses place in these valleys |
| Middle Section | after the streams have more water, the water carries material along and wears away the land. the areas in which the streams run form valleysusually are deep v shaeped. |
| middle sections characteristics | lateral erosion widens the valley profile river bends become pronounced forming meanders flood plain begins to form on th valley floor |
| river erosion | causes the river to widen. it is the grinding of rocks againt the river bed |
| lower section | when the river leaves the higher ground and enters flat plains. the river slows. the sidminet is deposited. when it floods the river will widen by many miles on both sides. |
| lowers section charcteristics | deposition is dominant, the valley floor had a broad flat flood plain/ the rier banks are marked. meanders and pronounced and oxbow lakes occur. deltas develop |
| silt | the rich soil carried by flooding rivers |
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