Drainage basin | geology | cypenv.info
The geology of a watershed is important because it influences topography, direction of water . The term accelerated erosion is often used to describe this. A drainage basin is any area of land where precipitation collects and drains off into a common . also seen as a way to build lasting peaceful relationships among countries. "What is a watershed and why should I care?". university of delaware. Retrieved ^ Lambert, David (). The Field Guide to Geology. they are based on measurements of watershed characteristics not influenced by .. Many potential mechanisms have been proposed to explain the relationship.
Antarctica comprises approximately eight percent of the Earth's land. Largest river basins[ edit ] See also: List of drainage basins by area The five largest river basins by areafrom largest to smallest, are the basins of the Amazon 7M km2the Congo 4M km2the Nile 3. The three rivers that drain the most water, from most to least, are the Amazon, Gangaand Congo rivers. Endorheic basin Endorheic drainage basins are inland basins that do not drain to an ocean.
The largest of these consists of much of the interior of Asiawhich drains into the Caspian Seathe Aral Seaand numerous smaller lakes. Some of these, such as the Great Basin, are not single drainage basins but collections of separate, adjacent closed basins. In endorheic bodies of standing water where evaporation is the primary means of water loss, the water is typically more saline than the oceans.
An extreme example of this is the Dead Sea. Importance of drainage basins[ edit ] Geopolitical boundaries[ edit ] Drainage basins have been historically important for determining territorial boundaries, particularly in regions where trade by water has been important. Bioregional political organization today includes agreements of states e.
Hydrology[ edit ] Drainage basin of the Ohio Riverpart of the Mississippi River drainage basin In hydrologythe drainage basin is a logical unit of focus for studying the movement of water within the hydrological cyclebecause the majority of water that discharges from the basin outlet originated as precipitation falling on the basin. A portion of the water that enters the groundwater system beneath the drainage basin may flow towards the outlet of another drainage basin because groundwater flow directions do not always match those of their overlying drainage network.
Measurement of the discharge of water from a basin may be made by a stream gauge located at the basin's outlet.Application of remote sensing in Geology
Rain gauge data is used to measure total precipitation over a drainage basin, and there are different ways to interpret that data. If the gauges are many and evenly distributed over an area of uniform precipitation, using the arithmetic mean method will give good results. In the Thiessen polygon method, the drainage basin is divided into polygons with the rain gauge in the middle of each polygon assumed to be representative for the rainfall on the area of land included in its polygon.
These polygons are made by drawing lines between gauges, then making perpendicular bisectors of those lines form the polygons.
The isohyetal method involves contours of equal precipitation are drawn over the gauges on a map. Calculating the area between these curves and adding up the volume of water is time consuming. Isochrone maps can be used to show the time taken for runoff water within a drainage basin to reach a lake, reservoir or outlet, assuming constant and uniform effective rainfall. A drainage basin is the source for water and sediment that moves from higher elevation through the river system to lower elevations as they reshape the channel forms.
Ecology[ edit ] The Mississippi River drains the largest area of any U. Agricultural runoff and other water pollution that flows to the outlet is the cause of the hypoxic, or dead zone in the Gulf of Mexico.
Drainage basin - Wikipedia
Drainage basins are important in ecology. As water flows over the ground and along rivers it can pick up nutrients, sediment, and pollutants. With the water, they are transported towards the outlet of the basin, and can affect the ecological processes along the way as well as in the receiving water source. Modern use of artificial fertilizers, containing nitrogen, phosphorus, and potassium, has affected the mouths of drainage basins.
While exact ages may not be clear, Yerkes et al. Pre-extension[ edit ] During pre- Turonianmetamorphosed sedimentary and volcanic rocks are present that serve as the two major basement rock units for the LA Basin. Large-scale movement along the Newport—Inglewood zone juxtaposed the two bedrock units along the east and west margins. Pre-basin phase of deposition[ edit ] The hallmarks of this phase were successive shoreline transgression and regression cycles.
Deposition of older marine and non-marine sediments began to fill the basin. Towards the end of this phase, the shoreline began to retreat and deposition continued. Basin inception[ edit ] After the deposition of the pre-Turonian units, there was a large emergence and erosion that can be observed as a major unconformity at the base of the middle Miocene units. During this time, the basin was covered by a marine embayment.
Rivers sourced in the highlands brought large amounts of detritus to the northeastern edge of the basin. Principal phase of subsidence and deposition[ edit ] The present form and structural relief of the basin was largely established during this phase of accelerated subsidence and deposition which occurred during the late Miocene and continued through the early Pleistocene. Subsidence and sedimentation most likely began in the southern portion basin. Until the rate of deposition gradually overtook the rate of subsidence, and the sea level began to fall.
Towards the end of this phase, the margins of the basin began to rise above sea level. During the early Pleistocene, deposition began to outpace subsidence in the depressed parts of the basin and the shoreline began to move southward. This movement caused the southwestern block to be uplifted relative to the central basin block. Basin disruption[ edit ] The central part of the basin continued to experience sediment deposition through the Pleistocene from flooding and erosional debris from the surrounding mountains and Puente Hills.
This infill was responsible for the final retreat of the shoreline from the basin. Deposition in the Holocene is characterized by non marine gravel, sand and silt. The southwestern block was uplifted prior to the middle Miocene and is composed mostly of marine strata and contains two major anticlines. The middle Miocene volcanics can be seen locally within the southwest block. Middle Miocene volcanics are also present. This block has a broad anticline that is truncated by the Santa Monica fault zone.
The central block contains both marine and non-marine clastic rock units interbedded with volcanic rocks that are late Cretaceous to Pliocene in age. Pliocene and Quaternary strata are most visible within the central block. Structurally, there is a synclinal trough.
There is also an anticline in the northeastern block. Basin stratigraphy[ edit ] Cenozoic Basin Stratigraphy Homogeneous evolution of this basin did not occur due to dynamic tectonic activity. Despite the active setting, there are over 9, m of strata within the basin.
It is common for rock units of the same depositional event to have different names in different locations within the basin. This may be a result of large variation in clast size as with the upper Pliocene Pico Formation in the northwestern part of the basin and the Upper Fernando Formation in the southwest part of the basin. This unconformity is used to correlate strata throughout the basin.
The record of the Cenozoic activity begins above this unconformity. The oldest basement units of this basin are of both sedimentary and igneous origin. The sedimentary unit was metamorphosed as a result of slippage of the Newport—Inglewood fault and is known as the Catalina Schist. The Catalina Schist can be found on the southwestern edge of the basin and is predominantly a chlorite-quartz schist.
Closer to the Newport—Inglewood fault zone, garnet-bearing schists and metagabbros occur. The eastern complex is characterized by Santiago Peak Volcanics. This rock unit contains andesitic breccias, flow, agglomerates and tuffs.
This bed sequence indicates an alluvial fan, meandering stream or braided stream origin. The Vaqueros Formation is marked by two sandstone, siltstone and shale units.
There are also characteristic mollusk fossils that indicate the area was dominately shallow marine. First is a basal marine conglomeratic sandstone, followed by a dominantly basaltic middle layer of multiple submarine lava flows and tuffs.