Exam 4 review
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GEOL 1302 - 002
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This 10 page Study Guide was uploaded by Athraa_Alherbi on Monday November 23, 2015. The Study Guide belongs to 1301 at University of Texas at Arlington taught by Andrew Hunt in Fall 2015. Since its upload, it has received 75 views. For similar materials see EARTH SYSTEMS in Geology at University of Texas at Arlington.
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Date Created: 11/23/15
1 o The main components of the climate system are the atmosphere hydrosphere cryosphere lithosphere and biosphere o The three basic parts of a stream 1 valley sloping area around the stream 2 channel bottom of valley 3 oodplain at area in valley level with top of channel 0 Whether a ow is laminar or turbulent depends on three factors 1 Its velocity rate of movement 2 Its geometry primarily its depth 3 Its viscosity which is a measure of a uid s resistance to ow The more viscous the thicker a uid is the more it resists ow The higher the viscosity the greater the tendency for laminar ow River Channel bottom of the valley Channel patterns meanders low sediment load low velocity 39OXbOW lakes point bars and cut banks braided streams high sediment load high velocity As a stream channel makes its way along the bottom of a valley it may run straight in some stretches and take a snaking irregular path in others splitting into multiple channels OThe channel may ow along the center of the oodplain or hug one edge of the valley In addition to straight stretches the two other types of channel patterns are meandering and braided River ValleyA stream valley encompasses the entire area between the tops of the slopes on both sides of the river 0 The cross sectional profile of many river valleys is V shaped but many other valleys have a broad low profile STREAM VALLEYS 10 11 The channel may occupy most or all of the valley bottom In lowlands where tectonic uplift has long since ceased stream erosion of valley walls is helped by chemical weathering and mass wasting 3 Flood plain In broad valleys a FLOODPLAIN a at area about level with the top of the channel lies on either side of the channel It is the part of the valley that is ooded when the river spills over its banks carrying with it silt and sand from the main channel 4 Mountains Streams0 In high mountains stream valleys are narrow and have steep walls and the channel may occupy most or all of the valley bottom 0A small oodplain may be visible only at low water levels In such valleys the stream is actively cutting into the bedrock a characteristic of tectonically active newly uplifted highlands 5 Braided streamsoThis is one whose channel divides into an interlacing network of channels which then rejoin in a pattern resembling braids of hair Braids tend to form in rivers with large variations in volume of ow combined with a high sediment load and easily erodible banks They are well developed for example in sediment choked streams formed at the edges of melting glaciers braided streams high sediment load high velocity 6 Meandering riversOn a great many oodplains channels follow curves and bends called meanders so named for the Maiandros now Menderes River in Turkey known in ancient times for its winding twisting course meanders low sediment load low velocity oxbow lakes point bars and cut banks Meanders are usual in streams owing on low slopes in plains or lowlands where channels typically cut through unconsolidated sediments fine sand silt or mud or easily eroded bedrock 7 Leveesby the channel Sediments build up low levees Successive oods build up natural levees ridges of coarse material that confine the stream within its banks between oods even when water levels are high Where natural levees have reached a height of several meters and the stream almost fills the channel the oodplain level is below the stream level Sediments deposited by ooding of a stream channel build up low levees 8 Cut ban kSChannel patterns meanders low sediment load low velocity oxbow lakes point bars and cut banks A cut bank also known as a river Cliff or rivercut Cliff is the outer most bank of a water channel stream which is continually undergoing erosion 9 Velocity of floodwaters As oodwaters spread out over the oodplain the velocity of the water slows and the current loses its ability to carry sediment The oodwater velocity drops most quickly along the immediate borders of the channel As a result the current deposits much coarse sediment typically sand and gravel along a narrow strip at the edge of the channel 10 Drainage networks are the patterns formed by the streams rivers and lakes in a particular drainage basinexit of the basin A map showing the courses of large and small streams reveals a pattern of connections called a drainage network If you followed a stream from its mouth to its head you would see that it steadily divides into smaller and smaller tributaries forming drainage networks that show a characteristic branching pattern 1 1 River erosion of solid rock 0 We cannot so easily see the erosion of solid rock Running water erodes solid rock by abrasion by chemical and physical weathering and by the undercutting action of currents One of the major ways a river breaks apart and erodes rock is by abrasion The sand and pebbles the river carries create a sandblasting action that wears away even the hardest rock Channels begin where rainwater draining off the surface of the land ows so fast that it abrades the soil and bedrock and carves into it Once a small gully forms it will capture more of the ow of water over the land surface and thus the tendency to cut down will increase As the gully progressively deepens the rate of downcutting increases because more water is captured The ability of a river to erode its bed depends on the river s discharge and slope 12 Laminar Flow of water In laminar flow the simplest kind of movement straight or gently curved streamlines run parallel to one another without miXing or crossing between layers The slow movement of thick syrup over a pancake with strands of unmixed melted butter owing in parallel but separate paths is a laminar ow Laminar ows of water can lift and carry only the smallest lightest claysized particles 13 Turbulent Flow of waterTurbulent ow has a more compleX pattern of movement in which streamlines miX cross and form swirls and eddies Fast moving river waters typically show this kind of motion Turbulent ows depending on their speed can move particles ranging from clay size to pebbles and cobbles 14 Saltation Sand grains in a ow typically move by SALTATION an intermittent jumping motion along the streambed The grains are sucked up into the ow by turbulent eddies move with the current for a short distance and then fall back to the bottom 15 Stream Capacity The total sediment load carried by a ow is its CAPACITY The velocity and the volume of a ow affect both the competence and the capacity of a stream Volume of ow 16 Stream Competence A ow s ability to carry material of a given size is its COMPETENCE As a current increases in velocity and coarser particles are suspended the suspended load grows 17 Evaporation Receding floodwaters leave behind standing ponds and pools of water The finest clays are deposited there as the standing water slowly disappears by evaporation and Part of this groundwater evaporates through the soil surface Another part is absorbed by the biosphere in plant roots carried up to the leaves and returned by 18 Transpiration Another part is absorbed by the biosphere in plant roots carried up to the leaves and returned to the atmosphere by TRANSPIRATION the release of water vapor from plants 198ublimationturns into gaseous state wout becoming a liquid first after evaporation 20 runoff precipitation relationship The sum of all rainwater that ows over the surface including the fraction that may temporarily infiltrate nearsurface formations and then ow back to the surface is called RUNOFF 21 precipitation in arid areas In warm arid or semiarid regions it rarely rains and water is a precious resource 22 Rock porosityThe space between grains intergranular porosity lThC space in fractures fracture porosity l The space created by dissolution vuggy porosity Porosity is higher in soils sediments and sedimentary rocks 10 to 40 percent than in igneous or metamorphic rocks where porosity is created mostly by fractures including joints and cleavage planes 23 Rock permeability In UNCONFINED AQUIFERS the water travels through beds of more or less uniform permeability that extend to the surface in both discharge and recharge areas Many permeable aquifers typically sandstones are bounded above and below by low permeability beds such as shales 24 An aqiclude These relatively impermeable beds are AQUICLUDES and groundwater either cannot ow through them or ows through them very slowly 25 Artesian well If we drill a well into a confined aquifer at a point where the elevation of the ground surface is lower than that of the water table in the recharge area the water will ow out of the well spontaneously Such wells are called artesian wells and they are extremely desirable because no energy is required to pump the water to the surface The water is brought up by its own pressure 26Aquifersa body of permeable rock that can contain or transmit groundwater Many permeable aquifers typically sandstones are bounded above and below by low permeability beds such as shales 27 Abundance of gases in the atmosphere Atmospheric composition The atmosphere is a mixture of gases molecular nitrogen 78 vol oxygen 21 vol Bother gasses argon carbon dioxide water vapor ozone methane etc 28 The cryosphereThe ice component of the climate system is called the cryosphere lt comprises 33 million cubic kilometers of ice primarily in the ice caps and glaciers of the polar regions Today continental glaciers and ice sheets cover about 10 percent of the land surface 15 million square kilometers storing about 75 percent of the world s fresh water 29 Lithosphere impact on climatewThe part of the lithosphere most important to the climate system is the land surface which makes up 30 percent of Earth s total area The composition of the land surface affects how solar energy is absorbed and returned to the atmosphere As the temperature rises the land radiates more energy as infrared waves back into the atmosphere and more water evaporates from the land surface 30 Albedo 6A rise in temperature reduces the accumulation of ice and snow in the 31 cryosphere which decreases Earth s albedo and increases the energy its surface absorbs The increased warming of the atmosphere enhances the temperature rise another example of POSITIVE FEEDBACK As the polar ice caps expand they re ect more solar energy back into space and the surface temperatures fall further an example of the albedo feedback Greenhouse gas effect The stimulation of plant growth by carbon dioxide increases atmospheric C02 which causes temperatures to rise by enhancing the greenhouse effect However more plant growth also removes C02 from the atmosphere by converting it to carbon rich organic matter thus reducing the greenhouse temperature rise This secondary effect is a NEGATIVE FEEDBACK 32 Relative humidity This is the amount of water vapor in the air expressed as a percentage of the total amount of water the air could hold at that temperature if saturated 33 Latitudinal variation in rainfall 34 Thermohaline circulation This is part of a general thermohaline circulation so called because it is driven by differences in temperature and salinity On a planetary scale the thermohaline circulation acts like an enormous conveyor belt running through the oceans that moves heat from the equatorial regions toward the pole 35 Ozone in the atmosphere Another minor constituent of the atmosphere is ozone 03 a highly reactive gas produced primarily by the ionization of molecular oxygen by ultraviolet UV radiation from the Sun ln the lower part of the atmosphere ozone eXists in only tiny amounts although it is a strong enough greenhouse gas to play a significant role in the atmospheric heat budget 36 Comparative discharge of the Amazon and Mississippi rivers The largest rivers such as the Amazon and the Mississippi can maintain some current many kilometers out to sea 37The Little Ice Age Q Drainage patterns 1 Dendritic characterized by branches similar to limbs of a tree 2 Rectangular develops on strongly jointed roclq terrain tends to follow joint pattern 3 Trellis develops in valley and ridge terrain where rocks of varying resistance to erosion are folded into anticlines and synclines 4 Radial patterns develop on a single large peak such as a large dormant volcano DEHDHJTIC trihutariee meet at IEN39J39EIFIQIES and hranch in randern l EE IiHE pattern Ferrn en reLIghlgr nlanar surfaces at cenrna39eterrthr eredahle reclze er eedirnent F LI HTJ39C HATT H CH EEI P L C HI EULA S I STEM J THELLlS Sherttrihutariee 539 H rneetlengtrunketrearneatnear right angles Few cennectiene hetlrleen trunlte F errn en felded er tilted eedirnentargr races at different reeietanceete ereeien P T M C E I STEM m an RECTANGULAR Straight trileutariee rneet etraight lUl39IIt etrearne Elende appreairnate right anglee Ferrn en faulted er ethe wiee fractured hedreclL ANGULAH drainage is similar but leendaljunctiene are at earne angle etherthan EIIII CD TT l39IIm CREE H UTA H 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