Geology Ch. 12 Running Water
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Where is Earths water?
- 97.2% of water is in oceans
- 2.15% is in glaciers and on land
- 0.65% is in the atmosphere, groundwater, lapes, swamps, and bogs.
- water is continuously recycled from the oceans, through the atmosphere, to the continents, and back to the oceans.
- Water vapor rises into the atmosphere where the process of cloud formation takes place.
- 80% of precipitation falls into Earths oceans.
- 20% falls on land
The surface flow in streams and rivers
water that is used by plants evaporates in this process.
Laminar and Turbulent flows:
- In laminar flows, lines of flow called streamlines parallel one another with little or no mixing between adjacent layers.
- In turbulent flows, streamlines intertwine, causing complex mixing within the moving fluid.
What does water during a rainstorm depend on?
- the maximum rate at which surface materials absorb water.
- intensity and duration of rainfall.
any surface water that moves from higher to lower areas in response to gravity.
a more or less continuous film of water flowing over the surface. Causes sheet erosion
- surface runoff is confined to trough like depressions that vary in size from tiny rills with a trickling stream of water to the Amazon River in South America.
- Rill, brook, creek, stream, and river.
water in any channel flows downhill over a slope nown as its gradient.
- a measure of the downstram distance water travels in a given time. m/s or f/s
- The velocity rises as the gradient falls.
- the volume of water that passes a particular point in a given period of time.
- In most rivers and streems, discharge increases downstream as more and more water enters a channel.
- Because of high evaporationa nd infiltration, the flow in some desert waterways decreases downstream until the water disappears.
What kinds of energy can a stream possess?
Kinetic and Potential Energy
the energy of position, the energy of water at high elevation. During stream flow, potential energy is converted into kinetic.
the energy of motion.
particales too small to see that are carried by a stream or river
the direct impact of running water, sets particles in motion.
exposed rock is worn and scraped by running water carrying sand and gravel
circular or oval depressions in stream beds. Formed where swirling currents with sand and gravel eroded the rock.
- consists of the smallest particles of silt and clay, which are suspended above the channe's bed by fluid turbulence.
- Gives water its murky appearance
larger particles, mostly sand and gravel, cannot be kept suspended by fluid turbulence so that it is transported along the bed.
grains move forward with the water, but also settle and finally come to a rest and then again move by the same process of intermittent bouncing and skipping.
collective deposits of rivers and streams
- an intricate network of dividing and rejoining channels separated from one another by sand and gravel bars.
- Develop when the sediment supply exceeds the transport capacity of running water, resulting in the deposition of sand and gravel bars.
- have a single sinuous channel with broadly looping curves known as meanders. The deeper side of a channel is known as the cut bank because greater velocity and fluid turbulence erode it.
- Flow velocity is at its minimum on the opposite bank, a point bar is deposited on this gently sloping inner bank.
- Meanders commonly become so sinuous that the thin neck of land between adjacent meanders is cut off during a flood, leaving an oxbow lake.
made when channels receive more water than they can carry and the overflow their banks and spread across adjacent flat plains.
made when a stream overtops its banks and water pours onto the floodplain, its velocity and depth rapidly decrease.
An alluvial deposit that causes the shoreline to build outward into a lake or sea, a process called progradation.
3 main types of marine deltas:
- 1. Stream-dominated - long fingerlike sand bodies, each deposited in a distributary channel that progrades far seaward.
- 2. Wave-dominated - also has distributary channels, but the seaward margin of the delta consists of islands reworked by waves.
- 3. Tide-dominated - continuously modified into tidal sand bodies that parallel the direction of tidal flow.
fan-shaped seposits of alluvium on land, form best on lowlands with adjacent highlands in arid and semiarid regions where little vegetation exists to stabalize surface materials.
- the arrangement of channels within an area.
- Dendritic: a network of channels resembling tree branching.
- Rectangular: characterized by right angle bends
- Trellis Drainage: a network of nearly parallel main streams with tributaries joining them at right angles.
- Radial Drainage: streams flow outward in all directions from a central high point, such as a large volcano.
- Deranged Drainage: characterized by irregularity, with streams flowing into and out of swamps and lakes.
- the lowest limit to which a stream or river can erode.
- Ultimate base level: sea level.
a stream with an equillibrium profile in which a delicate balance exists among gradient, discharge, flow velocity, channel shape, and sediment load so that neither significant erosion nor deposition takes place within its channel.
takes place when a river or stream has more energy than it needs to transport sediment, so some of is excess energy is used to deepen its valley.
valley walls of a river are undercut
phenomenon involving erosion by entering runoff at the upstream end of a valley.
the breaching of a drainage divide and diversion of part of the drainage of another stream,
erosional flood plains that formed when the streams were flowing at a higher level.
deep, meandering canyons cut into bedrock.
streams that flow directly through ridges that lie in their path.
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