THE GLOBAL ENVIRONMENT
THE GLOBAL ENVIRONMENT GEOS 200
U of L
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This 5 page Class Notes was uploaded by Benton Fisher III on Friday October 23, 2015. The Class Notes belongs to GEOS 200 at University of Louisville taught by Staff in Fall. Since its upload, it has received 19 views. For similar materials see /class/228380/geos-200-university-of-louisville in Geoscience at University of Louisville.
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Date Created: 10/23/15
Chapter 8 Description of Core Mantle amp Crust Core Inner core consists of solid iron under extremely high pressure amp temperature 6650 degrees C Outer core is liquid due to lower pressure Both have high densities Mantle Dense Rocky material Upper mantle can be divided in the 1 Asthenosphe re a quotplastic solid which can easily deform and flow like honey 2 Lithosphere together with crust forms the solid part of the earth there is less pressure in this section Allows tectonic forces break amp deform the crust very easily Differences between oceanic amp continental Crust 1 Oceanic Consists of thinner higher density basaltic rocks under the oceans Greater weight force on the earth Continental forms major land masses and is dominated by granitic rocks formed below ground age levels Iquot of iron magnesium less dense and lighter Continental Drift Theory The idea that continents and other land masses have shifted their positions during Earth history Pioneered by Alfred Wegener who noted many of Earth s continental coastlines fit together Seafloor spreading along mid oceanic ridges 1 Rocks on opposite side of ridges displayed similar magnetic properties amp age 2 Ocean floor rocks are young lt208 Million years old 3 Ocean rocks become younger towards midocean ridges The 3 Types of Plate Boundaries 1 Divergent Boundaries plates diverge at midocean ridges moving away from each other or the Sea Floor 2 Convergent Boundaries These are pushed together plates converge producing a subduction zone 3 Transform fault plates move laterally past each other between seafloor spreading centers These form mountain ranges Chapter 9 The 3 stresses that affect the crusttension compression amp shear Tension crust being pulled apart stretched apart Compression Pushed together shortened Shear twisted laterally EU The 3 Types of Crustal Deformation 1 Folding Convergent plate boundaries intensely compress rocks deforming them like thick layers of fabric stacked flat or table 2 Wraping produce up amp down bending of strata but the bends are far greater in extent Wraping features include small individual fold like structures called basin amp domes 3 Faulting Displacement of rock formations on either side of the fracture When rock strata are strained beyond their ability to remain a solid unit they express the strain as a fracture Be able to Identify 3 types of Faults 1 Normal Fault 2 Thrust or reverse Fault 3 Strike or Slip Fault Lateral shearing Orogeneses Related to Oceanic continental plate convergence 1 Oceanic Continental a Denser oceanic plate is subdivided forced beneath lighter continental plate Example Andes Rockie Mountains 2 Oceanic Oceanic a Denser oceanic plate subducts beneath the other b Forms volcanic island chains arcs Pacific volcanic island chains 3 Continental Continental a No subduction b Plates collide amp fold fault upwards instead Himalayas Definition of earthquake focus amp epicenter Earthquakes vibrations that occur when stress within the crust is suddenly released along a fault Focus Subsurface point where earthquake originates Epicenter point on Earth s surface which lies directly above the focus Tsunami formation Earthquake that takes place below sea level or on the seaocean floor Forms a large wave that grows as it reaches the shore Effusive amp explosive volcanic eruptions Magma involved amp resulting volcanoes Shield vs Composite 1 Effusive Eruptions a less violent but released more lava with larger flows b Gas released more readily at surface c ron rich mafic magma is hotter and more fluid like d Forms shield volcanoes 2 Explosive Eruptions a Occurs with cooler silica rich magma b Viscous magma prevents gases with from readily escaping c As pressure decreases towards Earth s surface gas is released quickly giving violent eruptions d Forms composite volcanoes Chapter 10 Importance of gravity for mass movement Gravity provides energy for erosional agents to denude and erode the land ice water etc Gravity also physically moves and deposits rock and debris downslope as mass movement Physical vs Chemical weathering processes Physical Physical Weathering Mechanical process which disintegrates rocks along jointfractures No Chemical Alteration Increases surface area of rock for chemical weathering Physical Processes 1 Frost Action a Freezethaw cycle b Water seeps into jointscracks c Expansion on freezing forces joint apart d Repeated cycle eventually fragments rock e Frequent in midhi latitudes and high elevation 2 Salt Weathering a Wettingdrying cycle b Same as frost wedging but utilizes salt crystal growth c Hence important process in arid and rocky coastal areas d Wetting deposits salt in rock e Drying causes salts to expand and force joints open 3 Pressure Release jointing a Spalling of curved rock shells parallel to rock surface exfoliation sheets b Common in batholiths c Decrease in surface pressure amp Expand in size d Often create exfoliation domes Chemical Weathering Decomposition of rock into constituent minerals via chemical processes Water and high temperatures acts as catalysts Hence common in humid tropical regions Chemical Processes 1 Hydration and Hydrolysis a Hydration water attaches to minerals weakening them b Hydrolysis H and O in water disassociate and combine with minerals to produce new substances c Grains expand to cause secondary physical weathering 2 Oxidation a Chemical union of oxygen with iron minerals to produce another substance b New Substance usually softer and weaker c Produces rust stains on rocks iron water hematite hence common in iron rich rocks basalt 3 Dissolution of Carbonates a Dissolution of soluble rocks by acidic water b Carbonic acid rainfall is naturally acidic c Water C02 H2CO3 d Carbon then combines with minerals to cause dissolution e Limestone particularly vulnerable Karst Environments Identify dominant chemical weathering process and doline formation 1 Sinkholes domines a Form collapsed roof b Or form a drawdown in the water table either from drought or human use 2 CravernsCaves a Water circulating below surface along joints and bedrock fractures hollows out large parts of bedrock below surface b Primary causedisappearing streams c Initiates collapsed sinkhole 3 StalactitesStalagmites a Depositional Karst features b Form over millions of years c Created when dissolved minerals precipitate out of groundwater d Unification of both are called columns Chapter 11 Base Level definition The level below which a stream cannot erode its valley Stream erosion processes hydraulic action and abrasion removal of rock material by flowing water 1 Hydraulic Action Erosion due to sheer force of moving water across bed and banks 2 Abrasion Erosion of bed and banks by material load being carried by river pot holes in stream bed Stream Load transportation Process 1 PPquot Suspension Saltation Traction Solution Chemical Load Definition of Discharge A streams volume of flow per unit time Locations of erosion and deposition along a meandering channel Occur on outside bend of meandering stream Forms llriver cliffsquot or llundercut banksquot Meandering Bends Material is eroded from outside meander and deposited by inside meander Deposition by streams occurs where stream velocity is reduced or when there is too much load Stream load can no longer be carried Location of Deposition Inside Bend of meander forms point bars Flooding across floodplain alluviam Mouth of River Alluviam fans Deltas Braided channels load deposited as bars along stream bed during times of low flow Difference between alluvial fans and deltas Deltas Occur when a river flows into an outlet Water no longer confined to a channel Reduction in velocity leads to deposition Forms a triangular shape fanning outwards Reshaped by coastal processes Alluvial Fans Similar to Delta s but occur on land Reduction in velocity associated with a stream leaving a mountain environment onto a level plain Also often associated with arid environments gtevaporation Stream rejuvenation and nickpoints When tectonic upliftsea level drop raises a portion oflongitudinal profile Allows rivers to cut down to base level Nickpoints mark point of change in profile nu i II I I l 1 VVdLCI fluuu39plain terraces
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