Geology Unit 3 Notes
Geology Unit 3 Notes GEOL 1610
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This 9 page Class Notes was uploaded by Olivia Brooksbank on Friday April 15, 2016. The Class Notes belongs to GEOL 1610 at University of North Texas taught by Johnny Byers in Spring 2016. Since its upload, it has received 22 views. For similar materials see Physical Geology in Geology at University of North Texas.
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Date Created: 04/15/16
Notes: Earthquakes 4/13/16 What is an Earthquake - Rapid release of energy from a source or (focus) - Bedrock moving against each other - the friction builds up when rocks cannot slide past and eventually there is a release in energy Cause of earthquakes - Plate tectonics - Volcanism (Magma chambers, increased pressure below surface) - Meteorite Impact - Atomic Explosions - Dam building - Injecting Fluids into the Ground Early earthquake warning systems - Chinese jar of water (Vibration would cause the marble to drop into frogs mouth) - Chickens - dogs - Elephants Waves - Surface Waves (Across/near surface of earth - Body Waves (within the earth) - Primary: Compress and pull thus changing both shape and volume of intervening material (P, push- pull, Granite moves 6 kmps, 10mph. water 1.5kmps, 1.5mph) - Secondary: Only change shape if intervening material (S, shake) Calculating distance - looking at the time interval between when the primary wave arrives versus the secondary wave because they are traveling at different speeds - Triangulation Richter Scale Measures two things: 1. Amplitude of the wave 2. Increase in energy released Occurrences of earthquakes - Quakes are predictable with respect to physical location - All FAULTS are where earthquakes can occur - Earth is highly faulted and they change with any change in pressure regime Tsunami: - Resulting form underwater earthquake or plate tectonic activity Notes: Glaciers 3/23/16 Reverend professor Buckland - 1784-1856 - Paleontologist - Shown in the field in Top Hat and Robes - Starting point for glacial studies - Looking far away for features Ignaz Venetz, 1788-1859 - Swiss engineer - Looking up close to glacial features St. Johns Bay Newfoundland - grooved and polished by glaciation LouisAgassiz - Father of modern glacial theory - Set out to prove Ignaz theory - proposed theory of great ice age Milutin Milankovitch, 1879-1958 - SiberianAstrophysicist - Suggested three astronomical events. TQ Three things that cause Glaciation: - Eccentricity (Change in shape of earths orbit - Obliquity (tilt) - Precision (Wobble) - (Procession shows the movement) 1. Variations in the Earth’s orbital eccentricity - the shape of the orbit around the sun 2. Changes in obliquity changes the angle that earths axis makes with the plane of earths orbit 3. Procession changes in direction of the earths axis of rotation Past major glacial Episodes Snow: - Snow forms from condensation of water vapor temperature below freezing - Internal arrangement of hydrogen and oxygen = Hexagonal symmetry - Stages of snow: Snow > granular > firn > Glacial (ice) What is a Glacier - Mass of ice, formed by the recrystallization of snow that has flowed under the influence of gravity - 100 feet of snow will compress into 10 feet of ice TQ -one ofACCUMULATION TQ More material is added by new deposition annually than is lost by melting Zone of ablation or melting TQ - More material is lost by melting and evaporation and deposited as snow - equilibrium line - upper and lower zones of an alpine glacier Two types of Glaciers: WETAND DRYTQ - Glacial Creep (Plastic flow): Move downhill by force of gravity. Fastest slow is at top middle.As glacier move over bumps, deformation causes crevasses to form in the rigid zone - Glacial sliding (Basal slip): Heat is generated at bottom of glacier due to friction and ground heat. Plastic zone of glacier is more fluid due to pressure Notes: Glaciers 3/23/16 Plastic slip: Occurs in exceptionally cold regions where glaciers basal ice is frozen into ground basal slip: occurs melted water caused at glaciers base Rates of Glacial Movement TQ - Imperceptible 8-76 mm per 1000 years in the sub polar region - Variegated Glacier inAlaska surges at regular intervals once every 17-20 years Glaciers erode rock in two ways: Plucking (Quarrying): Bedrock is pulled out by ice - proces a rock knob or ROCHE MOUTONNEE TQ - Abrasion: rocks and debris moved within the glacier cause linear erosive features, striations TQ Two primary controls on the formation of Glaciers - Latitude and Elevation determine glaciers TQ Glaciers: Two major types TQ - Alpine Glaciers (valley and mountain glaciers) occur in highland areas and flow down slope - Continental glaciers (ice sheets) occur at high latitudes and during ice ages at lower latitudes Formation ofAlpine Glaciers - Snow line = line above snow accumulates all year - Above the snow line snow accumulates thickens and changes form to a granular form called FIRN TQ - As the snow/firn is buried deeper it is compressed and recrystallized into glacial ice (deep blue form) - Cirque - where snow accumulates compresses and turns into ice - Valley glacier - moves down from - Cirque is the beginning of alpine glaciers Alpine glacier features TQ Glacial Creep: tresses cause the surface to crack (crevasses) Hanging valley TQ Smaller glacier rose less material so after glaciers retreat upon climate change hanging valleys waterfalls appear on the sides of the main valley Notes: Glaciers 3/28/16 TQ… Acirque is where the glacier forms Three or more intersecting glaciers on a mountain leaves behind a horn Ridges between glaciers are called aeries Acol is formed when the rock separating two adjacent cirques erodes, resulting in an ice field Glacial Milk: - runoff from glacier - milky because it has fine grain sediments in there - Minerals released - When water melted it left Loess - loess: Fine grain glacial product left behind Types of Moraines TQ: - - Terminal moraines: Furthest extent of glacial advance Recessional moraines: Left behind as glaciers retreat - Moraines that may be seen on the glacier as far bands… Later moraine (EDGE) mEDIAL mORAINE (MIDDLE) Continental Glacier - Also called an ice sheet - Covers LARGE areas - Extend over a body of water, we call them an ICE SHELF - Enormous weight causes land to subside in a process called IsostaticAdjustment - 70% Of earth is fresh water Evidence of ice age glaciations - Glacial drift = unsorted till + stratified drift - Till: Material Deposited in an unsorted mass at base of glacier - Stratified drift: sorted, layered debris carried by meltwater - Moraine: Ridges or mounds of glacial debris - Water flows through ice tunnels of base of glaciers and carried deposits forming structures called Eskers Saturated zone: Where groundwater is stored and can flow in aquifer Zone of aeration: Vadose one or unsaturated zone contains mixture of water and air Capillary fringe marks the lower boundary of the zone of aeration Permeability Permeability: Want permeable rock with high porosity…How well the pores and other empty spaces in the rock or sediment are connected: In other words how easily water can flow between the empty spaces in the rock An impermeable rock or mud layer is known as a confining layer, aquaclude or aquatard Confining layer - Stops water movement Aquaclude - Completely stops movement of water Aquatard - Slows down water The stream in the figure is called a effluent stream losing water is influent Notes: Glaciers 3/28/16 Confined vs Unconfined aquifer - Doesn't have a confining layer above it >>>Unconfined - Confined:An aquifer is sandwiched between two confining layers - Head pressure: How far up the water will travel on its own Darcy’s law Henry Darcy, mid 1800s Steeper the slope: The faster the water can run down the profile Velocity of ground water is proportional to slope of water table Hydraulic conductivity: flow varies with permeability of sediments and viscosity of fluids Notes: Movement of Water 4/1/16 Industrial Contamination - Solid Waste landfills: Seeping into the nearby water - Waste Pond - Factory Saltwater contamination: - Saltwater intrudes into fresh water aquifer HighPlains Aquifer is known as the Ogallala Aquifer, partially located in Texas Higher the mountain = More weathering Ogallala or High Plains Aquifer is the Largest in North American and possibly the world Seawaters are creeping into the aquifers Subsidence San Joaquin Valley - Lettuce fruit and veggies come from here - Drilling water to irrigate fields and make as much agriculture as we can - Drilling wells to pump groundwater Geologic work of Groundwater Caves (Caverns) and Karst - Accumulate water on surface, the more it stands the more calcium carbonate the more weathering in the limestone and takes advantage of the cracks with weathering, DISSOLUTION of limestone - Cavern: Underground - Cave: surface of cavern - Karst environment: Heavily weathered limestone Caves: - Soda Straw - Stalactites: hang - Stalagmites: floor - ALL DOMINATED BY CALCIUM CARBONATE Karst Formation 4 things: 1. Clean limestone, 80% calcium 2. Complex patterns of joints to form routes to subsurface draining channels (routes for water to make it below surface) Caverns hold more water, more water = more weathering 3. An aerated zone between the ground and the water table, animals contribute (burrows, roots) 4. Vegetation cover supplies varying amounts of organic acids (TREES, ROOTS…) that enhance the solution process Karst named for the Krs Plateau in Yugoslavia where first studied Sinkholes Some sinkholes are created by man Whirlpool: - Coriolis effect: ocean currents and air currents are effected by whirlpool - The whirlpool that developed temporarily reversed the normal direction of water flow Geyser: Magma chamber, superheated fluid ejected into the atmposphere (Old Faithful) Space and hydrologic regime change the geysers movement of water Calcium carbonate built up over opening of geyser Notes: Movement of Water 4/1/16 Faults - earthquakes - volcanoes - earthquakes Geothermal Energy: - Potent source of heat - Large porous reservoirs with channels connected to the heat source - Acap of low permeability rocks Notes: Streams and Hydrologic cycle 4/4/16 Importance of running Water - Greatest Impact = we depend on it for: (Personal use: 3000 gal month per person) Energy Travel Irrigation Hydrologic cycle: - Continually cycling fresh water through the atmosphere and back to the surface of the earth and the oceans - Transport, participate and give back to the cycle Terms: - Hydrologic cycle: the constant circulation of water from the sea, through the atmosphere, to land and its eventual return to the atmosphere by way of transpiration and evaporation from sea and land surfaces - Transpiration: the water infiltrates or soaks into the land and is absorbed by plants, which then release moisture back into the atmosphere (plant sweat) - Evaporation: (vaporization) is the process by which a substance passes from the liquid or solid state to the vapor state - Evapotranspiration:Aterm for the combined effect of transpiration and evaporation Fast water can do more work because it has more energy Streams, Creeks and Cricks - Stream Order: How much stream is being drained, drainage patterns - Rivers flow SOUTH usually - THEAMAZON DUMPS THE MOST MATERIAL BACK INTO THEATLANTIC OCEAN (MORE VOLUME) Stream Velocity: - Controlled by: 1. Gradient: Steeper the slope = fast water / Less steep = slow water 2. Shape: Size and roughness of channel 3. Discharge: How much water do you have to move if you have a lot of volume you will need to carry it faster - Waterfalls and rapids are associated with more stream gradient and increased erosion SLOPE…AND EROSION - Stream Gradient: Drop in elevation over a given distance. It is calculated by DIVIDING THE DROP BYTHE DISTANCE OR (RISE OVER RUN) (ELEVATION / river length) - STEEPER SLOPEAT THE HEAD WATERS -elocity changes with slope and shape of channel Same amount of water…speed up or slow down water depending on channel As the gradient decreases the discharge and overall velocity of the team system increases This has to do with how these drainages are constructed, the gradient is decreasing but the CHANNEL is getting bigger so it can carry more water, Function on how much water is receiving, a lot of volume so it much accelerate to carry the volume. Notes: Streams and Hydrologic cycle 4/4/16 Colorado river, UTAH dead horse point at right study site of John Wesley Powell in the 19th century. Established the concept of Base Level
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