Geology 101 Geology 101
Cal State Fullerton
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This 12 page Study Guide was uploaded by Michelle Ibrahim on Tuesday January 26, 2016. The Study Guide belongs to Geology 101 at California State University - Fullerton taught by R. Henderson in Winter 2016. Since its upload, it has received 149 views. For similar materials see Understanding The Earth in Geology at California State University - Fullerton.
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Date Created: 01/26/16
dStudy Guide for Exam 2, Geo 101 Henderson This list of terms is meant to crossreference your notes. It is not meant to supplant your notes (including videos shown) or the textbook. It is critical to read your text and attend lecture. This test will deal with recent chapters, but will assume a basic knowledge of the first four chapters. For example, you should know that rocks are made up of minerals, that granite is a continental igneous rock, what the shelf, slope, and abyss are, etc. In these chapters several terms not covered by me in lecture will be discussed but, if it is a term I haven’t covered specifically in class, then do not worry about memorizing that term. If you need any help studying please feel free to contact me at email@example.com or after class. Earth History Powerpoint Geologic Time Scale a relative scale, been around 100 years longer than absolute ages (ages from radiometric dates) uniformitarianism, geology gave Darwin time for natural selection (Hutton & Lyell) early age estimates of Earth from seawater & rx cooling(Kelvin’s based on cooling and sediment accumulation) Sediment Accumulation: >10^9 , Salt Accumulation (10 100 million) Cooling Rates 10100 million years, radioactivity 10 billion can be traced back to Nicholas Steno = father of stratigraphy Stratigraphic Record from Steno Stratification = layering that is diagnostic for sed. rxs I. Principle of Original Horizontality(states that most sedimentary layers of rock are deposited in a horizontal position.) II. Principle of Superposition (This principle states that in a sequence of undisturbed sedimentary layers or lava flows, the oldest layers are at the bottom) III. Crosscutting Relationships (the principle of crosscutting relationships states that the geologic feature which cuts another is the younger of the two features.) IV. Role of fossils Fossils show same age; certain fossils only at certaiMatching of rocks of similar ages in different regions is known as correlation which is typically done using fossils I & II = stratigraphic succession (chronology of geologic history which gives geologic time) Make sure you can complete block diagrams from homework/classwork Order of sed. rxs tells us if sea level changes Sea level changes Caused by large glaciers, plate tectonics or both Unconformities = a broken sequence between 2 rx layers or a gap in geologic time: if btwn 2 sed rx layers then and rock layers on either side of the unconformity are parallel disconformity if btwn a sed rx and underlying ign. Or meta. rx anmetamorphic or igneous rocks in contact with sedimentary strata then nonconformity if 2 rx layers (regardless of rx type) are not ll then angular unconformity EARTH HISTORY POWERPOINT SLIDES 3435 Formation = a series of rx layers that have the same physical properties & possibly the same fossils; gives a period of geologic time. Radiometric Dating = the use of naturally occurring radioactive elements to determine age U 238> Pb206 4.5 BA ½ life = time required for onehalf of the original number to 40 > 40 K Ar 1.3 BA decay see Fig. 9.15 Rb > Sr 47 BA C > N 5,730 What is the Importance of Geologic Time? ABSOLUTE DATING same thing as radiometric for igneous rocks. • Precambrian before 544 ma • Earliest fossils primitive bacteria 3.5 byr • Soft shelled organisms in ocean • First life at midocean ridges • Bacteria? Paleozoic 544251 ma o Before dinasaurs o Shelled organisms st o 1 in Cambrian Seas o Fossil trilobites from Europe and North America are the same showing they used to touch 400 MA Mesozoic 251 65 ma o Age of Reptiles o Not always fighting o notice these animals more familiar than those of the Paleozoic (crabs, conch, seasnail, o Cenozoic life (65mapresent Age of Mammals Human ancestors – 3 ma Paleogene Titanoboa Regression vs. Transgression rapid transgressions(faster) often associated with unconformities (water erosion) regressions contract the marine shelf realm so extinct more likely eustatic events are global changes in sea level. Large eustatic rises result in a large amount of marine sediment deposited on the continent (sequences) and the formation of epicontinental seas (ex. Cretaceous Interior Seaway of North America). eustatic changes from rate of tectonic activity (rising SL) a. seafloor spreading producing submarine mountain changes b.tectonic uplift of coast eustatic changes from glaciers and subsidence (falling SL) POWER POINT MASS WASTING Mass wasting =the downhill movement of geological materials due to gravity Angle of repose = maximum angle at which a slope of loose material will lie without cascading down. Differs whether wet or dry or whether sand or clay Sediments either Consolidated (cemented) or Unconsolidated (loose & uncemented) UnSaturated water in some pore spaces binds particles Saturated water between all particles, keeps them apart and allows them to flow. Mass Movements from fast to slow: a) Rock falls – rapid, rock leaves surface b) Rock slides – rapid, like rx fall over 100 mi/hr but rx still on surface (can become frictionless but still a connection to land surface c) Landslides – same as rockslides but with soil & rock d) Mudflows – heavy precipitation liquefy ground (soil only) earthflows same as mudflows but soil & regolith e) Slumps – pieces of a hill slide down a little bit and form a depression. Scarp above and bulge beneath f) Hill creep – the very slow to almost unobserved movement of materials down a slope. Usually measured as a fraction of an inch. apparent in all hills, seen from trees Rock slides are all similar: 1) need a valley 2) stratified rocks 3) abundant water, precipitation 4) triggering mechanism, i.e., earthquake 5) Water bedded shale helps lubricate base of slides (Ex Gros Ventre 1952) What are ways slope can become less stable or more stable? More water more likely it will make it less stable, also height and weight of the rock on top of its base. Triggers – Excess rainfall (or water leaks from pools, excess watering) – Earthquakes (plate tectonics) – Loss of vegetation (fires, logging) – Rapid accumulation of materials • For example, lahars from Pinatubo • Adding fill (weight) to roads, building sites POWER POINT STREAMS Streams = major geological agents operating on the land surface average velocity of a stream not constant. Streamany flowing body of water (rivers big ones) v increases towards center & surface, v=0 at the bottom discharge = total volume of water flowing past a point in a given time period. D= v * A D= discharge; A=area (ave width * ave height) D and v increase downstream with increasing water from tributaries Competence vs. Capacity Capacity (how much) the total amount of sediment that a stream can carry. Capacity increases with discharge (direct relationship) Stream transport Competence = (how big) refers to the size of a particle a stream can carry. Direct relationship with discharge, increase together. • Streams transport material in 4 ways: – Solution • Dissolved particles (calcite) – Suspension • Solid particles carried in water – Saltation • Skipping along the bottom – Bed load • Pushing and rolling along on the bottom, but never rising up into the fluid 1) large pieces roll & slide = bed load transport 2) materials move by sudden jumps = saltation 3) small grains suspended, usually clay & silt particles down the length of river/stream = suspension 4) dissolved materials in water, i.e., iron oxide or 3aCO = solution. Makes hard water. – Floodplain = flat area on either side of channel within val The relatively level area surrounding the flowing water Area where river meanders. Differs depending on – Amount of water – Amount of sediment – Gradient (slope) of land point bar (deposition) vs. cutbank (erosion); oxbow lakes = when cutbanks cut themselves off; natural levees Drainage basin = area of land that a river & tributaries drain Grades beds (fine = point bar; coarse =delta) • loss of elevation = loss of potential energy. Floods: Where can they occur? Usually? Flood Plain recurrence interval or 100year flood is the height to which a river will rise, on average, every hundred years. What is the 50year flood? Probability of the 50 yr flood each year is 2% Dams 6000+ large dams in US alone Water resources and uses: Dams block sediment transport & alter the base level & store tremendous potential energy Waterfalls caused by one rock below eroding faster than the rock layer above Mudstone Erodes Faster Than Dolostone =Waterfall. Same goes for rapids DELTA’s (most active area compared to rivers because it: has a loss of river power, more flooding & more sediment) Streams point slide 51, difference. For rivers: the higher the current speed, the less the sediment load, ex: Colorado Ground Water Power Point Groundwater How it flows? Uses? Flows just like surface water just slower, 50% of drinking water from Groundwater, 40% of water for irrigation Porosity = total void space within a rx; given as percent groundwater stored in small spaces btwn grains; Vol. of void space/ Rx Vol. = % porosity Permeability = interconnectedness of all the pore spaces Igneous Rxs 0% porosity Metamorphic Rxs 010% porosity Most Sedimentary Rxs (lime&sandstone) 1050% porosity Shale 510% porosity Shale also 0% permeability so no fluid (caprock) Aquifer = bed (layer) of rx (typically sed.) with high porosity and high permeability Aquiclude = bed of rx with 0 permeability, i.e., shales Groundwater table takes place between unsaturated zone (air& water filled pores) and saturation zone (zone with completely watery pores) Groundwater mimics topography of the land. (discharges through riverbeds ect.) Flows much slower than surface water, impermeable ROCK SHALE Contamination: leachate, undetachtd leak, spray leads to contaminated aquifer (buried gasoline and industrial chemical storage tank., wastedisposal well, pesticides) Problems associated with its used: drawdown due to pumping allows saltwater to rise, the solution to this drawdown problem is barrier wells. Wind and Deserts * Different amounts of solar energy are absorbed at different latitudes. * Interaction of the ocean and atmosphere moderates surface temperature, shapes Earth’s weather and climates, & creates waves and currents. * Earth’s rotation causes the Coriolis effect(the observed deflection of a moving object, caused by the moving frame of reference on the spinning Earth.), the apparent curvature of the path of moving air. * Large storms are spinning masses of unstable air that develop between or within air masses Atmospheric motion driven by temperature gradient from equator to poles. The lower atmosphere is a fairly homogeneous mixture of gases. Water vapor occupies up to 4% of the volume of the atmosphere The density of air is influenced by temperature & water content Nitrogen 78, oxygen 20, argon .9, Carbon .033% composition of atnospohere Air moves from high pressure(dry and hot) to low pressure (stormy, windy cold) but complicated on Earth because it is in motion. In the Northern Hemisphere air turns to the right. In the Southern Hemisphere air turns to the left. Wind belts: trades (surface winds of the Hadley cells), westerlies (Surface winds of the Ferrel Cells), polar easterlies; what causes? Coriolis effect (in N. Hemisphere deflect to the right or eastward). Strongest at equator; weakest poles. High (stable) vs. Low pressure. Warm air/ Cold air/ Cold air Warm air Storms associated with low pressure (counterclockwise in N. Hem. and clockwise in S. Hem.). Where winds come together L pres. = rainfall; where winds diverge H pres. = deserts & polar deserts Jet Stream strong western winds at top of temperate zones (due to high air density & air temperature gradients). Rain to Seattle not here. Storms always with Low Pres. Hurricanes biggest Storms= regional atmospheric disturbances. Storms have high winds & precipitation ( Low pressure and air rising from the ground) Updrafts (where the storms hot air rises), cyclones = rotating masses of LOW Presure Air moves in cells. A large circuit of air is called an atmospheric circulation cell. Three cells exist in each hemisphere. Hadley cells are tropical cells found on each side of the equator. Ferrel cells are found at the midlatitudes. Polar cells are found near the poles. The doldrums are calm equatorial areas where two Hadley cells converge. L The horse latitudes are areas between Hadley and Ferrel cells. There is little surface wind in this area. H Deserts = area with low annual precipitation <25 cm/yr. Wind can dominates sed. Transport most deposits come from water » At the midlatitudes, cooling, dry air from the Equatorial regions create semipermanent high pressure that prevents moist air from entering these areas. » In the western US, mountainous regions collect moisture leaving dry air masses moving eastward, thus producing deserts. Desert pavement Over time, the surface becomes smooth interlocked stones: desert pavement. can’t be transported by wind. Deflation removes finer particles and leaves a desert pavement. Loess deposits blanket of finegrained sediment particles, fertile but easily eroded, prone to flash floods • DesertificationTransformation of productive land to nonproductive land • Factors: – Poor farming practices – Overgrazing – Drought – Result is vegetation gone, nothing to hold finer materials & they blow away – Ex: Dust Bowl in 1930’s, China, Africa Dry wash Playa lakes • Alluvial fans – mixtures of gravel, sand and silt that are deposited along mountain fronts. • Evaporites – halite, gypsum and calcium carbonate deposited on playas due to the evaporation of water. Glaciers = An accumulation of ice that is thick enough to move under its own weight, occurs when ice reaches 300 feet in thickness, maximum thickness of ~ 11,000 feet. Ice originates from snow: partially melted & refreezes (compacted & dense) to create fern that compacts & becomes a mass of ice • Glaciers grow at high elevations (cold, wet) and melt at low elevations. • Glaciers occupy former river channels and move downslope due to gravity. • Rocks are picked up and transported by the moving ice – Transported rocks grind and erode the rock over which the glacier travels. – Transported rocks may be deposited when ice melts. – Poorly sorted deposits • alpine: restricted to mountainous systems (photo below) • continental: covers extremely large areas 2 • Antarctica: 12,500,000 km up to 3 km thick, 80% of the ice on earth, 65% of the fresh water Glacier came down from north plowed through south, 30 glacial events occurred. 100 years to form, 10 to melt 59 average temperature of the entire planet, ice age 54 degrees F Glaciation in North America Thicker in NOrth Albedo(reflecting of snow) Ice crystals similar to igneous rock. Why? Glacier can mimic underlying topography: crevasses open at a drop in a glacier down to 50m (why only this depths). Close after flowing over topographic change. Types of glaciers Continental glaciers (aka ice sheets or ice caps) vs. Valley (alpine) glaciers Landscape features of glaciers Erosional widens & deepens valley from river V to glacial U much steeper so w/out glacier more prone to landslides Depositional Moraine = a landform comprised of till, unlayered transported material that is deposited by a glacier, which has undergone no sorting. Dumped like a truck: Lateral, End (types), & Medial. Erratics – ice results in very poorly sorted deposits, large boulders w/ clay. Pleistocene Glaciation Never Kick Idle Workers Afterwards You’ll be Sorry Glacial vs. Interglacial Nebraskan (~300,000 yrs ago) Aftonian Kansan (Biggest more south) (~200,000) Yarmouthian Illinoisian (100,000) Sangomonian Wisconsinian (10,00030,000) lot of small & large advances & retreats throughout Pleistocene (last 2 MA). Earlier in Geologic Time? Milankovitch cycles: 1. Eccentricity (orbit shape0 0 2. Tilt (axis shift from 21.5 to 24.5 ) 3. Precession (wobble of rotating Earth) Snowline; Zone of ablation; Flow line Causes: sliding of ice sheets? Ocean circulation & plate tectonics Most glaciers are melting Dangers of climate change Coasts Humans try to influence coastal processes: Groins Seawalls Importing sand largely ineffective in solving beach erosion shorelines and beaches Running Refrigerator affect made antartica MORE GLACIER QUESTIONS EARTH HISTORY MOST nd Atmosphere 2
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