Geo Test 4 PDF

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Professor Vaughn. Class and reading notes with SI notes ...

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Chapter 9 1. Plate Tectonics i. Plate tectonics: the theory of tectonic activity, which deals with lithospheric plates and their motions 1. Movement of these plates is driven by heat from Earth’s core 2. Slab pull: responsible for most movements of plates a. Bigger the subduction area the faster the plate above is being pulled ii. High plateaus: crustal uplift iii. Plains: found in stable continental regions iv. Mountains: active or former collisions of tectonic plates v. Hills and low plateaus: low relief landforms created by erosion or by deposition of sediments b. Major relief features of the earth’s surface i. Passive continental margins: no strong tectonic activity within 50 million years ii. Active continental margin: deep offshore trenches, volcanic activity c. Types of Plate Boundaries i. Extensional tectonic activity: 1. Spreading boundary 2. Plates pulled apart 3. Rifts ii. Compressional tectonic activity: 1. Converging boundary 2. Plates pushed together iii. Plates move past each other 1. Transform boundary 2. Transform faults iv. Spreading boundary: a boundary where two lithospheric plates move apart. Also, called a divergent boundary. 1. A crack occurs and continually filled with magma rising from the mantle 2. Forms new oceanic crust when magma emerges in the form of lava at the oceanic spreading centers 3. Midoceanic ridge: the central belt of submarine mountains where two plates separate 4. Rift Valley v. Convergent boundary: a boundary where two lithospheric plates come together 1. Subduction: one plate slides under the other

2. Two plate collide creating a mountain range 3. Sites for intense tectonic and volcanic activity vi. Transform boundary: a boundary where two lithospheric plates slide past each other without colliding 1. Plates move along a nearly vertical fracture that extends down through the entire lithosphere 2. Dead sea fault marks the transform boundary between the African Plate on the west and the Arabian Plate on the east vii. Two basic forms of tectonic activity 1. Compression: lithospheric plates are squeezed together along convergent lithospheric plate boundaries 2. Extension: happens along spreading boundaries where the plates are being pulled apart d. Subduction Zones i. Subduction: descent of the edge of a lithospheric plate under an adjoining plate and into the asthenosphere 1. One plate is denser and thinner than the other, it is forced to slide beneath the less dense, thicker plate ii. Plates push against each other at a convergent boundary iii. Oceanic trenches: a narrow, deep depression in the seafloor representing the line of subduction of an oceanic lithospheric plate beneath the margin of a continental lithospheric plate. Descending plate pulls material into the asthenosphere 1. Mariana Trench 2. Japan Trench responsible for Great Tohoku earthquake of 2012 3. Andes mountains e. Collison Zones i. Two continental crust collide ii. Folds: corrugations of strata caused by crustal compression iii. Orogeny: means mountain making. the folding of crust where two continental plates meet contributes to a mountain-building process 1. Himalayas 2. Appalachian iv. Anticlines: the arch in folds of the Earth’s crust 1. Usually form broadly rounded mountain ridges 2. Up fold v. Synclines: U-shaped base of folds in the Earth’s crust 1. Create open valleys 2. Down fold

vi. Overthrust faults: form of faulting in which slices of rock move over the underlying rock on fault surfaces with gentle inclination angles f. Differential erosion of strata i. The ways fold areas erode to form sequential landforms depends on the rock strengthens of different strata ii. Weaker formations (shale and limestone) erode to leave long, narrow ridges of hard strata (sandstone or quartzite) g. Continental Suture i. Two continents can converge to eliminate an ocean between them ii. A continental suture permanently unties the two plates, so that there is no further tectonic activity along that collision zone iii. Appalachian and Ural Mountains 2. Tectonic Activity and Earthquakes a. Faults and Fault Landforms i. Fault: a sharp break in rock associated with a slippage of the crustal block on one side of a tectonic plate with respect to the block on the other 1. Depth can be several kilometers 2. Fault slippage varies (I cm to 15m) ii. Four main types are characterized by how the crustal blocks move 1. Normal: a variety of fault in which the fault plane inclines (dips) toward the downthrown block and a major component of the motion is vertical a. Faults occur when the crust on one side of normal fault drops down relative to the other side 2. Strike-slip: a variety of fault on which the motion is dominantly horizontal along a near-vertical fault plane a. Faults are produced when tectonic plates move past each other horizontally 3. Reverse: a type of fault in which one fault block rides up over the other on a steep fault plane a. Are produced by compression in the crust 4. Overthrust: fault characterized by the overriding of one crustal block (or thrust sheet) over another along a gently inclined fault plane; associated with crustal compression a. Involve mostly horizontal movement. One slice of rock rides over the adjacent ground surface iii. Fault scarp: a cliff-like surface feature produced by faulting and exposing the fault plane; commonly associated with a normal fault. presence of a newly exposed cliff face. Can indicate how much the fault moved iv. Graben: a crustal block dropped down between two normal faults

1. Two plates are pulling apart and the middle plate is going to drop down v. Horst: a crustal block pushed up between two normal faults vi. The Balcones Fault Zone 1. Roots of Ouachita Mountains (300 million years ago) 2. Area of weakness. Why you have the springs in SA and San Marcos 3. Subsidence of coastal plane b. Earthquakes i. Earthquakes: a trembling or shaking of the ground produced by movements along a fault. 1. When tension reaches critical point, the fault slips, relieving the strain ii. Epicenter: the location of the earth’s surface directly above where a fault slipped to produce an earthquake. iii. Focus: location where the fault slipped iv. Magnitude: amount of energy released by an earthquake 1. Can be measured by the amplitude of the seismic waves produced 2. Related to the length of the section of the fault that broke 3. Richter scale. Logarithmic (graph on slide 23) c. Tectonic Environments of Earthquakes i. Blind faults: not apparent on earth’s surface and scientist don’t know where they are located. ii. P waves iii. S waves iv. Epicenters are calculated by triangulating the readings from three different seismometers reading center, using the difference in travel times for P and S waves v. Subduction zones 1. Greatest earthquakes including those in japan, Alaska, North America, Central America, and Chile 2. Java Trench 9.0 earthquake and resulting tsunami (2004) 3. Tohoku 9.0 earthquake and tsunami (2012) vi. California earthquakes, identified as circles with size proportional to the earthquake magnitude, are overlaid on top of delineated and mapped fault lines vii. Spreading center earthquakes mostly occur along mid-ocean ridges viii. The New Madrid earthquakes of 1811 are an example of quakes away from plate boundaries ix. Space based instruments imaging earth’s movements (inSAR)

1. Landform deformation of tectonic stresses after the Northridge, California earthquake x. Shaking experience depends on 1. Earthquake magnitude 2. Location in relation to epicenter and direction of rupture 3. Local soil and rock conditions 3. Volcanic Activity and Landforms i. Magma: underground molten mineral matter ii. Lava: magma that has reached the surface iii. Volcano: a conical or dome-shaped structure built by accumulation of lava flows and volcanic ash 1. Many volcanoes are located on subduction boundaries or rift zones b. Tectonic Environments of Volcanoes i. Volcanic activity is related to plate movement ii. Hotspot: a center of volcanic activity thought to be located over a rising mantle plume c. Volcanic Eruptions i. Lahar: hot as combines with melting snow, racing down the side of a volcano in a hot mudflow ii. when lava is forced out of a volcano violently, in the form of a volcanic eruption, it is a severe hazard iii. Atmospheric impacts 1. Affects global warming (the year with no summer was Mt. Tambora in 1815. the volcano releases greenhouse gases) 2. Volcanic ash and gases have been shown to affect global weather and surface temperatures for months or years after an event iv. Monitoring 1. Green is for the least hazardous 2. Red is for the most hazardous d. Types of Volcanoes i. Shape, size, and explosiveness of a volcano depend on the type of magma involved ii. Magma comes from two main types of igneous rock: felsic and mafic iii. Felsic lava: (rhyolite and andesite) very thick, gassy, and gummy, with high viscosity 1. Doesn’t flow far from volcano and will build up to make steep slopes 2. Produce explosive eruptions 3. Pyroclastic material: (tephra= volcanic ash) collective name for ejected particles from an erupting volcano

iv. Stratovolcano: a volcano constructed of multiple layers of lava and volcanos ash. 1. Most common associated with felsic magma 2. Thick, resistant to flow 3. Builds steep slopes around volcanic vents 4. Tall steep cone with crater 5. Most active are found on circum-Pacific mountain belt 6. Hold large amounts of gas under high pressure 7. The eruption can change the shape of the volcano 8. Caldera: great central of depression that remains after the explosion v. Mafic lava: (basalt) not very viscous and holds little gas. Eruptions are usually quiet and lava can travel long distances to spread out in thin layers 1. Volcanoes are broadly rounded domes with gentle slopes vi. Shield volcano: a low, often large, dome-like accumulation of basalt lava flows emerging from long, radial fissures on flanks 1. Most common associated with mafic lava vii. Flood basalts: large-scale outpourings of basalt lava to produce thick accumulations of basalt over large areas viii. Cinder cones: small volcanoes that form when frothy magma is ejected under high pressure from a narrow vent e. Tsunami is Japanese for “harbor waves” i. Tsunami: train of sea waves triggered by an earthquake (or other seafloor disturbance) traveling over the ocean surface ii. Caused by sudden vertical displacement of ocean water iii. Triggered by: 1. Large earthquakes that cause uplift or subsidence of sea floor 2. Underwater landslides 3. Volcanic Flank Collapse 4. Submarine volcanic explosion 5. Asteroids: can produce Mega-tsunami 100 times higher than one produced by quake

Chapter 10 1. Weathering i. Denudation involves first weathering, then mass wasting, and finally erosion by wind ii. Weathering: all the processes that physically disintegrate or chemically decompose a rock at or near the Earth’s surface 1. Exposure of rocks to surface elements 2. Water, temperature change, atmospheric agents, biotic agents iii. Mass wasting: the abrupt or incremental downhill movement of soil, regolith, and bedrock under the influence of gravity iv. Erosion: the wearing away of the Earth’s surface materials by wind and water b. How Rock Disintegrate i. Regolith: the layer of rock and mineral particles that lies above bedrock ii. Bedrock: the solid rock layer under soil and regolith, which is relatively uncharged by weathering iii. Vulnerability of rock surfaces to weathering depends on: 1. how much of the rock is exposed 2. existing climate conditions 3. the ability of water, air, and microscopic organisms to penetrate the exposed surface iv. Joints: fracture within the bedrock, usually occurring in parallel and intersecting sets of planes v. Pores: small space between grains of rock surface where the axis emerges c. Physical Weathering i. Physical weathering: the breakup of massive rock (bedrock) by physical forces at or near the earth’s surface 1. Mechanical weathering 2. Fractures rock in to smaller pieces without chemical alteration of the minerals ii. Frost cracking: the physical weathering process that occurs when water penetrates joints or pores in the bedrock and freezes under certain conditions to break the rock by expansion 1. Also, called wedging 2. Dominant process in arctic and high-mountain environments iii. Salt-crystal growth: a form of wreathing in which rock is disintegrated by the expansive pressure of growing salt crystals during dry weather periods when evaporation is rapid 1. Growth occurs in arid and semiarid regions

iv. Exfoliation: the process of removal of overlying rock load from bedrock by processes of denudation, accompanied by expansion and often leading to the development of sheeting structure 1. Rock is exposed at the surface, releasing pressure, so rock expands slightly 2. Unloading v. Thermal action: cracking of rocks by unequal stresses between mineral grains that develop as rocks heat and cool vi. Biological action 1. Lichens 2. Animals 3. Roots vii. Sheeting structure: rock joints in layers parallel to surface, forming exfoliation domes d. Chemical Weathering i. Chemical weathering: the decomposition or decay of minerals in rocks by chemical reactions with water, oxygen, and acids ii. Hydrolysis: the chemical union of water molecules to form different, more stable mineral compounds 1. minerals react chemically with water iii. Oxidation: the chemical union of free oxygen with metallic elements in minerals, which makes minerals unstable and causing rock to degrade in strength and crumble iv. Carbonation: process whereby carbonic acid weathers rocks by slowly dissolving minerals 1. Carbonic acid: a weak acid that is formed when carbon dioxide dissolves in water 2. Dissolving limestone and creating caverns 3. Weathers buildings, tombstones 2. Slopes and Slope Processes i. Colluvium: a deposit of sediment or rock particles accumulating from overland flow at the base of a slope and originating from higher slopes where sheet erosion is in progress ii. Becomes alluvium if water transports and deposits the debris farther away from the slope base 1. Alluvium: sediment laid by a stream that is found in a stream channel or in low parts of a stream valley subject to flooding iii. Angle of repose: maximum angle at which debris, sand, or rock of a given size can rest before the force of gravity causes it to slide downslope b. Forces on Slopes i. Climate

1. Amount and timing of water that infiltrates or erodes slope 2. Type and abundance of hillside vegetation a. Arid regions prone to rock falls, debris flow and soil slips b. Humid regions prone to complex landslides, earth flows, and creep ii. Vegetation 1. Function of climate, soil type, topography, and fire history 2. Vegetation provides protection cover that slows surface erosion 3. Roots add strength and cohesion to slope materials 4. Vegetation adds weight to slopes iii. Water: 80% of landscape you see 1. Water saturates soil causing soil slips and debris flows 2. Slumps develop after deep infiltration of water 3. Water erodes base of slope to decrease stability 4. Water can cause spontaneous liquefaction or quick clay a. Fine grained material that loses strength when disturbed and flows like liquid iv. Time 1. Forces change with time 2. Driving and resisting forces change with season due to change in moisture content or water table 3. Chemical erosion occurs slowly over time a. Carbonic acid from plants dissolves limestones 3. Mass Wasting a. Earth materials moving down slope due to gravity i. Factors such as the steepness of the slope, type of material, and water content determine whether the material 1. Creeps 2. Falls 3. Slides 4. Flows downhill b. Creep i. Soil creep: the extremely slow downhill movement of roil and regolith 1. Slowest form of mass wasting ii. Solifluction: a type of earthflow, found in arctic permafrost regions caused by soil that is saturated with water and then deformed into terraces 1. occurs when soils become thoroughly saturated with water and slowly flow downslope by gravity 2. may occur in periglacial environments

c. Falls i. Rockfall: the most visible form of mass wasting, in which rocks fall down steep slopes or cliff sides, bringing with them soil or regolith ii. Talus: (scree) an accumulation of rock fragments falling from a rock face or cliff, collecting at the bottom in a cone-shaped pile d. Slides i. Landslide: a rapid sliding of large masses of bedrock on a steep mountain slope or form a high cliff 1. Rotational and directional displacement 2. set off by earthquakes, sudden rock failures, steep slopes ii. Effects of landslides 1. Can do significant damage a. in united states 25 people are killed each year, damages>$1 billion b. people hit with or buried in falling debris c. slides may damage homes, road, and utilities d. slides may block roads, impeding travel or block streams causing flooding e. disease iii. Snow Avalanches 1. Loose-snow avalanches a. Widen as move downslope 2. Slap avalanches a. Move as cohesive block b. More dangerous and damaging c. Triggered by overloading slope or zones of weakness in the snowpack 3. Avalanches move down chutes a. Avoiding these areas can minimize hazard e. Flows i. Mass wasting of earth materials with high water content results in flows ii. May occur in deserts and after wildfires 1. Rotational 2. Transitional iii. Rotational slide: a type of landslide in which the mass rotates as it slides downslope, resulting in displacement of soil from the top of the rupture iv. Transitional slide: a type of landslide in which the mas moves out and down the slope with little or no rotation v. Earthflow: the moderately rapid downhill flow of water-saturated soil, regolith, or weak shale

vi. Mudflow: a flowing mixture of water and soil or regolith that flows rapidly downhill vii. Lahar: mudflows on the slopes of erupting volcanoes 1. See Volcanic Eruptions notes 2. Mudflow or debris flow composed of slurry of water, pyroclastic material, and water- flowing typically from a volcano viii. Debris flow: a stream-like flow of muddy water heavily charged with sediment of wide range of size grades, including boulders, generated by sporadic torrential rains upon steep mountain watersheds f. Induced Mass Wasting i. Mass movements produced by human activity ii. Scarification: a general term for artificial excavations and other land disturbances for extracting or processing mineral resources g. Identifying potential landslides i. Crescent shaped cracked or terranes on hillside ii. Tongue-shaped area of bare soil or rock on hillside iii. Large boulders or talus piles at base of cliff iv. Linear path of cleared vegetation extending down a hill v. Exposed bedrock with layering parallel to slope vi. Tongue-shaped masses of sediment at base of slope vii. And irregular land surface at the base of a slope viii. Information can be used to create slope stability map or hazards map h. Prevention of landslides i. Drainage control 1. Keeps water from infiltrating a slope 2. Drains can divert water 3. Impermeable layers can keep water from infiltrating ii. Grading can increase slope stability 1. Material from upper slope can be moved to base iii. Slope supports 1. Retaining walls: concrete or filled wire baskets

Chapter 12 1. Erosion, Transportation, and Deposition i. Erosional and depositional landforms 1. Peaks (E), ravines (E), fans (D), canyons (E), floodplain (D) b. Slope Erosion i. Rills: a small channel in the soil or regolith caused by erosion from heavy rain ii. Gullies: a deep, V-shaped trench carved by overland flow and/or headward growth of a small stream during advanced stages of accelerated soil erosion iii. Deposited particles accumulate in a thickening layer called colluvium iv. In arid and semiarid climates, erosion can be more rapid or severe v. Forest fires and areas with no foliage can speed up soil erosion vi. Erosion rate is slow in humid climates vii. Vegetation needed to resist erosion c. Stream Erosion i. Hydraulic action: stream erosion by the force of impact of flowing water upon the bed and banks of the stream channel 1. Water drags on the bed 2. Can rapidly erode loose alluvial materials such as gravel, sand, silt, and clay when the river flow is high ii. Abrasion: the erosion of bedrock of a ...