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Study Guide, Everything after spring break Material Type: Notes; Professor: Sims; Class: 012 - Earth History and Resources; Subject: Geoscience; University: University of Iowa; Term: Spring 2011;
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Deserts Desert: an area where annual precipitation is less than potential water loss by evaporation. Steppe: semi-arid borders of deserts. *Dry regions (steppes and deserts) cover 30% of Earth’s land surface (~42 million km^2 ) Types of deserts o Hot and Dry: warm all year (very hot in summer). Very low rainfall that often evaporates in air o Semiarid: summers long and dry, winters have low precipitation, rainfall very low but concentrated when it does come. o Coastal: semi-long warm summers, cool winters. Rainfall low and in short bursts. o Cold: short warm summers, long cold winters with snow. High precipitation in winter. Where deserts form o Low-latitude: 20-30 degrees N and S. In high pressure zones. o Mid-latitude: areas by mountains o Rain shadows: winds move precipitation to one side of mountain leaving arid desert on other o Continental interior: inlands of large land masses. *Weathering is mostly mechanical instead of chemical *Most desert erosion is the result of running water *Rain rare but usually very heavy resulting in flash floods and a lot of erosion *Rivers usually form outside of desert in mountains and pass through. Groundwater: water table usually very deep forming oasis where it intersects the surface *Deserts have poor drainage systems; most runoff does not reach sea causing erosion Landscape evolution o Early: often driven by block faulting and tectonic uplift of mountains. Running water and streams also contribute o Late: mountains lower and basins fill with sediment. Alluvial fans: form at canyon mouth Playa lakes: form in flat central area of un drained desert basins Bajada: an apron of sediment along a mount front Inselbergs: isolated mountain remnants Wind o Transport: moves particles and can result in dust and sand storms Suspended load: fine particles transported within the air Saltation: transport of particles through a series of bounces Bed load: particles moved along the ground surface by wind (creep) o Erosion: Deflation: wind lifts loose sediment and leaves behind larger grains Blowout dunes: depression excavated by wind Yardangs: wind sculpted ridges Ventifacts: stones with flat ridges o Deposits: form dunes and loess Loess: wind silt accumulates, extremely fertile farm land Dunes: hill or ridge of sand Transverse: series of long rides perpendicular to wind Longitudal: parallel with wind Barchans: shaped like crescent with tips pointing downwind Parabolic: tips point into with instead of with wind
Shorelines Shoreline: line that marks the contact between land and sea (constantly moving) Coastline: coast’s seaward edge; landward limit of the effect of the highest storm Wind-generated waves: provide most of the energy that shapes and modifies coastal zones Crest: high point of a wave Trough: low point between two waves Wave height: distance between trough and crest Wave length: horizontal distance between two crests Formation of waves: wind is primary factory. Energy transfers from wind to water through pressure and friction Oscillation waves: occur in open water, water travels in circular orbits. Rock back and forth Effect of Shallowing: water moves increasingly elliptical towards floor. Crest heights increase and wave length gets shorter. Turbulent water advances up shore and forms surf. Translation Waves: turbulent advance of water created by breaking waves in shallows Shore Zones o Offshore: seaward of where waves break at low tide o Nearshore: zone between where waves break at low tide to low-tide level o Foreshore: area between low-tide and coastline; most active area, typically wet o Backshore: area inland of foreshore, affected by storm waves and high tides. Wind effects Wind Erosion o Wave impact and pressure erode land o Abrasion from rock fragments erode as well Beaches: waves act to accumulated sediment along land o Form from breaking waves moving sediment. Shoreline features: vary by rockiness of shore, currents, wave intensity, and whether the coast is stable, sinking, or rising Terrace: flat area exposed during low tide composed of fine grained sediment Berm: ridge of poorly sorted sediment from waves at upper limit of high tide Dunes: hill of fine grained sand relative to shore. Can go for miles or be stopped by cliffs Emergent coast: when coast rises or sea level drops. Cliffs retreat while beach extends at base o Jagged cliffs, wave-cut notch or platforms. Can form sea caves or sea stacks. Submergent coast: sea level rise or land subsides. o River valleys become estuaries (drowned river mouths), hills become islands. Highly irregular shoreline Factors of erosion and deposition: degree and type of tectonic activity; topography and composition of land; configuration of coastline and nearshore; prevailing wind and weather patterns; proximity to rivers Wave Refraction: waves slow as they enter shallow waters o Concentrated against sides and end of headlands, forms beaches and irregular coastlines. Erosion will eventually straighten out coastline. Oblique Waves: flow parallel with coast instead of perpendicular. Cause current to flow parallel making longshore current. Beach drift: oblique waves and longshore current cause sediment to move along beach in zigzag pattern Baymouth Bar: a sand bar that completely crosses a bay Tombolo: a ridge of sand that connects an island to the mainland or other island Barrier Island: low sand ridges formed parallel to coast Shoreline stabilization: man-made structures that prevent erosion o Sea wall: parallel to shore and close to beach, stops waves from reaching shoreline o Breakwater: parallel to shore: protects from large breaking waves o Groin: short wall built at a right angle to trap moving sand o Jetty: pair of structures built to protect harbors against storm waves and deposition
Composition: created by layers of gases surrounding planet, retained by gravity. Mainly nitrogen (78%) and Oxygen (21%) Origin: gases were trapped from volcanic eruptions. Ancient atmosphere consisted of water vapor and carbon dioxide. Without atmosphere Earth would be 60 degrees cooler. Oceans: started when water vapor accumulated producing precipitation. Rain turned into runoff into large basins producing oceans Hydrologic Cycles: runoff and groundwater dissolved salts and carried into ocean, water moved from oceans to atmosphere by precipitation and salt concentrated in oceans. Atmospheric Layers: denser gases sink, 90% in troposphere, no distinct upper limit. o Layers (top to bottom): Exosphere (600km), Thermosphere (90km), Mesosphere (50km), Stratosphere (10km), Troposphere (where we are, ground level) Ozone: layer within stratosphere with high concentration of ozone molecules, absorbs UV, thickness varies from year to year and is thinner at Poles. Temp of Atmosphere: Troposphere cools with altitude, ozone heats upper stratosphere, mesosphere cools with altitude. Uppermost layer is coldest place on earth. o Thermosphere and Exosphere: oxygen molecules absorb solar radiation, temp increases with altitude until gas is too thin to have effect o Auroras: solar winds drive charged particles into upper atmosphere, colorful lights. o Troposphere: convections moves air here, air parcels displace others. Coastal Breezes: wind direction changes from day to night because of temp differences o Sea breeze: during day, air moves from sea to land o Land breeze: during night, air moves from land to sea because of water’s retention of heat Atmospheric Convection: moving air masses create pressure zone (low where they begin, high where they’re going). Air masses create wind when moving from high to low pressure zones o Barometric pressure: force per unit area exerted by atmosphere on surface beneath or within it. Adiobatic Changes: gas changes pressures so temp changes o Heating: air sinks, pressure increases and forces parcel volume to contract o Cooling: air rises, pressure decrease and parcels expand Cloud Formation: rising air is moist; water vapor condenses to water droplets as parcels cool. o Low pressure zone: converging winds to rising air mass, cloud formation and precipitation o High pressure zone: diverging winds from sinking air, clear and cool weather Cyclones: low atmospheric pressure produces inward spiraling wind. Hurricanes: tropical cyclones, sustained near-surface winds exceed 73 mph Tornadoes: small cyclones with strong winds, tube like condensations funnel from rotation cloud. Weather fronts: transition zone between air masses of different densities. Extend horizontally and vertically and are marked by cloud formation. Clouds: visible mass of condense water or ice suspended in atmosphere o Types are defined by altitude and whether they are layered or convective o Formed by orographic uplift, most winds forced up by hills, cool and precipitate on wind side o Convectional lifting: air mass is warmed and rises, then expands and cools higher, clouds. o Frontal lifting: convergence of air masses; warmer, moister air mass will override cooler o Radiative cooling: air above ground cools and turns to fog after sun sets. Precipitation: condensation of atmosphere water vapor that falls to surface Thunderstorms: form when an air mass with a lot of condensation is forced upward rapidly in an unstable atmosphere, where temperature drops. Lighting: electricity resulting from differently charged particles in air. Typical of thunderstorms Global wind patterns: result from temp-driven convection, adiabatic effects, coriolis effect, and seasonal shifts
o Convection: circulates air by the unequal warming at different latitudes o Variation in moisture levels: results from evaporation and condensation. Patters cause cool dry air to sink. o Coriolis: deflects air currents to right in northern hemisphere and left in southern. o Seasonal changes: solar heating of Earth’s surface affects distribution of high and low pressure areas. Seasonal Variations: result from variation in solar radiation reaching ground. The bariation happens when the tilt of earth’s axis rotates. One part of planet gets more sun as result Mid-latitude seasons: seasonal latitude marked by changes in earth’s axis Equatorial seasons: amount of precipitation often varies more than temp resulting in distinct seasons Monsoon: heavy rainy season that lasts for several months with lasting climatic effects *Temperature varies more in continental interiors than on coasts
Distribution of Fossils: may be found in sedimentary rock but most common in rocks formed in environments with rapid deposition and minimal diagenesis. (review map) Process: first something dies, then it is buried, then diagenesis takes over. Remains must survive long enough to be discovered Enemies of preservation: destructive scavenging, transport of organism by wind or water, or slowed delayed deposition of sediment (oxygen = decay). Deposition environment: an organism that dies in a place where it can be immediately buried is more likely to fossilize Autochthonous: organisms preserved in their original position Allochthonos: fossil assemblages preserving organisms that were transported prior to deposition Bioturbation: organisms burrowing through sediments. Dissolution: hard parts can and will dissolve from certain pH levels or other chemicals Diagenesis: physical and chemical changes during lithification of sediment Metamorphosis: folding or heating of fossiliferious rocks Exposure: rock must be exposed or discovered to be studied (erosion, uplift, drilling, etc.) Modes of Preservation: o Body Fossil: preserved remnants of an organism o Ichnofossil: tracks, burrows, or other indications that living organisms were present Trackway: series of tracks or footprints left by a single organism. Can provide info on tissue, movement, and behavior of organism. Coprolites: fossilized feces can show diet of species. Burrows: shows info on behavior, preserved when burrow is flooded and filled with sediment Hard vs. soft parts: soft tissue is less likely to be preserved than bone, shell, wood, etc. Permineralization: pore spaces in hard parts are filled by minerals from ground water Replacement: pore spaces and other parts are completely replaced with minerals (mostly wood) o Petrifaction: Silica binds to cellulose and crystallizes and preserves it. Compression: 2D, often distorted. Physically compressed organism by overlying sediments Impression: organism is lost but imprint is left in sediment, details preserved o Molds and Cast: mold is the impression, it is a mirror image. A cast fills the mold and leaves a replica of the organism Lagerstatte: extraordinary fossil deposit o Conservation: a deposit with preservation of morphology (soft parts that are usually not found) o Concentration: exceptional taxonomic preservation, due to high preservation rates. Resin Fossils: mode of fossilization that often preserves morphological detail. Usually plants or insects are trapped in tree sap or amber and are completely reserved in their original state. Taphonomy: study of all processes that happen between death of an organism and fossilization Preservation rates: used to asses completeness of a fossil record Taphonomic Filters: o Number of parts: the more an organism has, the more are likely to get lost o Population Abundance: the more of an organism that existed, the more likely it is to be fossilized Live-dead study: a census of the organisms living in an ecosystem is compared to the species preserved in the sediment. Life assemblage to death assemblage. Used to find preservation rates *Study slides on page 7 for percentages of organisms fossilized in a certain community Spatial sampling: finding the percent. Most fossil assemblages are part local, part regional Biodiversity and Extinction
Taxonomy: the classification, identification, and the naming of organisms. Started by Carl von Linne o Linnean Taxonomy: a method of classifying living things in a ranked hierarchy. Similar organisms are a species, similar species are a genus, and similar genus is a family. o Binomial nomenclature: species get a two part name. Genus name and species name ( Homo sapien ). First name capitalized, second not. Always italicized or underlined. Describing species: scientists write a summary of new taxon’s characteristics such as traits it shares and those that make it unique. Peer-Review system: to publish, a scientist sends work to an appropriate journal, 2-4 other scientists review the topic, and author accepts/rejects changes. Type Specimen: a specimen identified as the example of the taxon illustrated by the formal description Taxonomic Relationships: species with common ancestors and similar traits are categorized together Phylogeny: relationship among species. Closely related species are branched together while others are branched apart. Stratigraphic Range: the duration of time between the oldest occurrence of a fossil species (origin) and the youngest occurrence of that species (extinction). Basically duration of a species Phanerozoic marine animal biodiversity: graph on page 5, slide 4 Diversity turnover: average stratigraphic range is 5-20 million years. About 99% of all species that have ever lived on Earth are now extinct Origin of Atmosphere: gases were trapped from volcanic eruptions. Ancient atmosphere consisted of water vapor and carbon dioxide. Without atmosphere Earth would be 60 degrees cooler. Precambrian: spans first 4 billion years of Earth’s history. Hadean (4600 to 4000mya), Archean (4000- 2500mya), and Proterozoic(2500 to 542mya) o Physical and Chemical Weathering: out gassing produced acidic conditions (accelerated chemical weathering). Precipitation and runoff increases physical weathering, sediment deposits and salinity Precambrian Oxygen: photosynthetic organisms started producing oxygen about 3.5bya. o Banded Iron Formations: early iron oxide deposits accumulated on the seafloor as alternating layers of iron-rich rocks and chert. o Stromatolites: distinctively layered mounds of calcium carbonate and filamentous bacteria o Red Beds: evidence of chemical oxidation (especially iron) in continental sediments Great Oxidation Event: 2.4bya excess oxygen released in atmosphere, became toxic to dominate organisms (anaerobic bacteria), and led to ecological crisis then metabolic revolution. Ozone in Atmosphere: harmful to most cells: ocean water shields marine organisms. Formed in UV radiation. Became protective layer allowing organisms out of Deep Ocean. Prokaryotes: organisms lacking nucleus or other membrane-bound organelles. Mostly unicellular. Eukaryotes: cell that engulfs another cell. Membrane bound organisms o Grypannia: multicellular eukaryote. o Bangiomorpha: sexual eukaryote. Intercalary pattern of cell division. Vendian biota: oldest fossil evidence of multicellular organisms. (Algae, lichens, etc.) Doushantuo Microfossils: from late Proterozoic marine rocks in southern china. Appear to preserve embryos of ancient organisms. Embryos: go through a rapid series of cell divisions, without cell growth or cell differentiation cleavage. Burgess Shale: rocks that preserve a 500ma ecosystem from the sea floor. Paleozoic invasion of land: animals and plants evolved to protect against solar radiation, dehydration, and breathing oxygen. Insects and plants eventually moved to shore. Lobe-finned fishes adapted and became first amphibians. Iowa Carboniferous. About 300mya Iowa was warm and humid. Extensive swamps and tree ferns. Swamp plants became coal deposits over time after compression Mass Extinctions: an event when there is a massive decline of life and biodiversity. 5 in Phanerozoic. Causes of Cretaceous/Tertiary Extinctions: probably asteroid impact accompanied by volcanic eruptions, climate change, and wildfires.
Energy Resources Nonrenewable: form or accumulate over millions of years, so quantities are considered fixed (Coal, iron, natural gas) Renewable: virtually inexhaustible or can be replenished relatively quickly (sun, wind, tides) Consumption: U.S. energy consumption has increased over last 100 years. Usage of different resources has also changed. Review graph page 1, slide 5 and map slide 6 Fossil Fuel: general term for any hydrocarbon (organic material) that may be used as fuel (coal, natural gas, bitumen from oil sand and oil shale) Coal: readily combustible sedimentary rock formed by compaction of plants over millions of years o Single most used energy resource world-wide o Limited resource, mining can cause major environmental damage and air pollution Oil and Natural gas: consist of hydrocarbons from marine plants and animals. Takes millions of years. Must accumulate between cap rock and reservoir rock. o Cap rock: a rock impermeable to oil and gas o Reservoir rock: a porous and permeable rock. Oil Trap: A geologic environment that allows significant amounts of oil and natural gas to accumulate underground o Anticlinal trap: rising oil and gas collect at a fold apex in an up-arched series of sedimentary strata o Fault Trap: upward migration of oil and gas is trapped where displaced strata bring a dipping reservoir rock opposite an impermeable bed. o Salt Dome: Rising oil and gas accumulate in deformed, upturned sandstone beds adjacent to salt dome. o Stratigraphic trap: trapped by an original sedimentary structure: a sloping bed of reservoir rock thins to point of disappearance (pinches out) Drilling: Cap rock is punctured. Oil and natural gas under pressure migrate from pore spaces to surface. Stored in tanks Oil Sands: a mixture of clay and sand combined with water and bitumen. Several substantial deposits exists but major environmental drawbacks and expenses exist when drilling Oil Shales: fine-grained sedimentary rock with enough organic material to yield oil or gas. Currently too expensive with current technology Gas Hydrates: a solid form of water that contains large amounts of methane within its ice-like crystals. Hydraulic Fracturing (Fracking) process for artificially increasing a reservoir rock’s permeability to get oil and gas. o Fluid is pumped into rock causing it to fracture. High pressure forces gas out o Large amounts exist but can contaminate water and cause earthquakes. Biofuels: fuel derived from biomass (recently living organisms). Renewable but produce greenhouse gases. BioEthanol: most common type of biofuel. Obtained from starch or sugar found in many crops. Switchgrass: a hardy, perennial grass native to North American prairies, considered good candidate for biofuel. Rapid growth and in large quantities. Doesn’t need to be replanted. Wind Energy: wind pushes objects creating kinetic energy. Windmills make this kinetic energy into electricity. Iowa is 2nd^ largest producer of wind energy next to Texas.
Mineral Resources: Mineral Resources: naturally occurring useful and essential minerals from Earth’s crust, ultimately available commercially according to value (iron ore, lead, tin, copper, zinc, mercury, bauxite) o Reserves: already identified deposits of minerals that can be extracted profitable o Known-deposits: exists but are not economically or technologically recoverable yet. Ore: rock containing useful metallic minerals that make it valuable for mining. Magmatic Segregation: local concentration of minerals formed during cooling and crystallization of magma o Separation of heavy minerals that crystallize early o Enrichment of rare elements in the residual melt Diamonds: form of carbon created at great depths under high pressure, once crystallized diamonds are carried up through conduits within ultramafic rock called kimberlite pipes. Hydrothermal deposits: solutions of hot, metal-rich fluids move through rock, depositing metals (usually as sulfides) as the fluid cools. Among best known and important minerals o Vein deposits: solution moves along fractures, cools, and precipitates within cracks o Disseminated deposit: ores precipitated as minute masses throughout entire rock mass o Surface deposit: where magma is near surface, dissolved metals precipitate when water cools in air. Metamorphic ore deposits: many of important deposits are produced by contact metamorphism (Sphalerite, Galena, Chalcopyrite) Produced by Contact metamorphism and regional metamorphism. Secondary Enrichment: concentration of scattered, minor amounts of metals by weathering processes. o Chemical weathering and water percolation remove undesirable elements from decomposing rock o Desirable elements found near surface are carried to lower zones, and concentrated. o Examples: copper, silver, bauxite Bauxite: principal ore of aluminum, formed by secondary enrichment in rainy climates. Placer Deposits: formed when heavy minerals are mechanically concentrated by currents, most commonly streams and waves; typically heavy and durable minerals. (gold, tin, platinum, diamonds) Nonmetallic Mineral Resources: o Building materials: Natural aggregates (crushed stone, sand, gravel) Gypsum (plaster and wallboard) Clay (tile, bricks, and cement o Industrial Minerals: Fertilizers (nitrate, phosphate, and potassium compounds) Sulfur (sulfuric acid to manufacture phosphate fertilizers) Salt (used in chemical industry, softening residential water, and keeping street ice-free)
Earth’s Systems: Geosphere, Hydrosphere, Atmosphere, Biosphere Answers to recent clicker questions (should be recognizable on test)