Physical Geology
The hydrologic cycle
- Evaporation from oceans
- Precipitation on the land and water
- Run off through streams and rivers, back to the ocean
- Groundwater infiltration, then reemergence in rivers and streams
- Transpiration by plants (absorption then release by plants)
- Freezing of water on ice sheets and snow
- Amount of water on Earth is constant, and it is always circulating through this hydrologic cycle.
- Running water does 3 things:
1) Erosion
- - overland flow by mass wasting brings in material to rivers and streams
- - water also acts like a hot knife in butter, and cuts down through the soil and rocks in flows on. Material it cuts through is worn away by the running water
- - coarse sediment in the water acts like the sharp edge to the knife.
2) Transportation
- - competence of a stream: a measure of the maximum size of particles a stream can transport, from large to small.
- - capacity: maximum amount of material (sediment) a stream can carry
- - streams and rivers transport weathered particles of rock and soil away from a source area, to be deposited at a later time in a different place.
3) Deposition
- - whenever water velocity decreases, some sediment will be deposited.
- - sorting: particles of similar size deposited at the same time, depends on the critical settling velocity of a certain particle size
- - well sorted material is called alluvium.
- Oceans represent 71% of the Earth's surface
- If the Earth were smooth & level, the oceans would cover the Earth to a depth of approx 6000 ft.
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