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Physical Science Notes

Running Water and Ground Water

The Water Cycle

326 million cubic miles of water

97.2% oceans

2.16% ice sheets and glaciers

0.65% lakes, streams, subsurface water, atmospheric water

 

transpiration:absorption of water by the plants and subsequent release back into the atmosphere

oceans: evaporation is greater than precipitation

land: precipitation is greater than evaporation

Running Water

stream: any channelized flow of water

stream velocity: distance water travels per unit time

highest velocities near cent of channel just below surface

Range: 0.5mph to 20mph

 

Factors that determine velocity

Gradient: slope of stream channel, steeper means more velocity however it is not the only factor.

Shape, size, and roughness of the channel affects friction; larger channels have more efficient flow.

 

Discharge:

Mississippi - 611,000 cubic feet per second

Amazon (World's largest river) 12X more than the Mississippi

 

Changes from Upstream to Downstream: headwaters to mouth

Base level is the lowest point to which stream erosion could lower land.

 

Ultimate base level sea level

Temporary base level resistant layers of rock

Work of Streams

erosion
removal of rock and soil
transportation
dissolved load
suspended load
bed load: saltation, rolling, sliding
deposition
Mississippi transports 750 million tons to the Gulf of Mexico each year.

 

Competence: maximum size of particles it is capable of transporting

Capacity: maximum load it can carry

 

As stream velocity slows competence is reduced and particles settle out; largest first. Solid particles of various size are sorted.

Alluvium:
sorted material deposited by a stream.
Deltas:
deposits due to abrupt decrease in velocity
Distributaries:
small channels in a delta
Natural Levees:
Build up bank parallel to the river's course.
Artificial Levees:
Built to control flooding. Steeper slopes than natural levees.
Backswamps:
marshes formed from poorly drained levees.
Yazoo Tributaries:
tributaries that flow parallel to the river until they can breach the levee and enter the main channel

Stream Valleys

Youth:
Narrow V-shaped valleys, rapids, waterfalls (created by differential resistance to weathering)
Niagara Falls - resistant dolomite over less resistant shale; has retreated 7 miles upstream
Maturity:
Wide valleys, flood plain, meanders, no rapids or waterfalls
Old Age:
Wide valleys, flood plain is wider than meander belt, oxbow lakes, natural levees, backswamps, yazoo tributaries
Rejuvinated:
entrenched (incised) meanders, terraces (remains of old flood plain), active down-cutting.

 

Every stream has a drainage basin. The land area that contributes water to the stream is the drainage basin. Drainage basins are separated by divides.

 

Continental Divide: Pacific Ocean // Gulf of Mexico

Groundwater

85% of fresh water is glacial ice
14% of fresh water is ground water
0.5% of fresh water is in lakes and reservoirs

Work of Groundwater

caverns

Groundwater sustains sterams during times of no rainfall.

 

Rain: evaporates
absorbed by plants and transpired back to the air
runs off
soaks into the ground (subsurface water>

The zone of aeration is separated from the zone of saturation by the water table.

The water table is not perfectly level, it follows the countours of the surface somewhat.

Wetlands and swamps occur when the water table is at the surface.

 

Movement: porosity is the percentage of rock consisting of pore spaces
permeability is the ability to transmit water freely

Generally the smaller the pores the slower the water travels through the rock

Limestone Caverns

17,000 caves in the United States

 

Famous caves Carlsbad Caverns (Southeastern New Mexico)
Mammoth Cave (Kentucky)

Depositional features in caves: travetine limestone, dripstone: stalactities and stalagmites

 

Karst Topology landscape shaped by the dissolving power of groundwater evidenced by sink holes.