Geology Facts

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Geology Facts. Earth’s Layers. The Earth consists of a solid inner core (Fe and Ni), a liquid outer core (Fe and Ni), a plastic-like mantle (Si, O, Fe, Ni), and a thin rocky crust (Si, O). The lithosphere is the crust and upper mantle.
Geology Facts Earth’s Layers
  • The Earth consists of a solid inner core (Fe and Ni), a liquid outer core (Fe and Ni), a plastic-like mantle (Si, O, Fe, Ni), and a thin rocky crust (Si, O).
  • The lithosphere is the crust and upper mantle Ocean crust (made of basalt) is thinner, younger, and denser than continental crust (made of granite).Convection currents move tectonic plates. Hot material rises, cools, becomes more dense, and sinksConvergent boundaries are colliding plates which cause folded or thrust faulted mountains, subduction zones, (volcanic and trenches) and reverse faults (thrust faults)Reverse FaultNormal Faulttransform, lateral, slip-strike faultDivergent boundaries are dividing plates and cause sea-floor spreading, mid-ocean ridges, rift valleys, and volcanoes. Normal faults are produced from this movement.Transform boundaries slide past each other and strike slip faults and earthquakes are produced.Earthquakes can result with any plate movementHot spots are not related to plate movementA fault is a break or crack in the Earth’s crust where movement has occurredVolcanic activity is associated with subduction, rifting, or seafloor spreadingAn ocean plate will always sink under a continental plate because it is more dense, creating a trenchAppalachian Mountains are folded mountains3 seismic stations are always needed to find the epicenter of an earthquakeEarthquake Waves
  • P waves travel the fastest and reach the seismic station first. P waves travel through solids and liquids. P waves slow down and bend when they hit the liquid outer core.
  • S waves do not travel through liquids.
  • L waves, surface waves cause the most damage
  • Most volcanoes and earthquakes occur in the “Ring of Fire.”The San Andreas Fault is responsible for the earthquakes in CaliforniaThe North American Plate is traveling in a westward courseThe Pacific Plate is traveling in a northwestern courseThere are 3 kinds of volcanoes, shield, composite (also known as strata), and coneMagma is found underground and lava is above groundMinerals
  • A mineral is found in nature, inorganic, solid, with a definite chemical composition and structure. (crystalline)
  • Mineral properties depend on their atomic structure Ores are useful and profitable
  • Ores of Common Metals
  • Contains: bauxite, bornite, chalcopyrite, chalcocite, pit ore, magnetite, hematite, specular hematite, galena, pyrolusite, garnierite, sphalerite, chromite, stibnite, and molybdenite.Minerals are determined by their streak, cleavage, fracture, hardness, color, luster, and special properties
  • Streak- The color of the mineral in powder form. This test is done by rubbing the mineral across a white streak plate. Several minerals have a streak that is not the same color as the mineral itself. Most metallic luster minerals have a dark colored streak
  • Cleavage and Fracture
  • Cleavage or Fracture- If a mineral breaks along flat, smooth surfaces it shows cleavage. Cleavage can be in one, two or three directions. Some examples are:
  • Mica- cleavage in one direction, see the diagram below (upper right),
  • Feldspar- cleavage in two directions, see the diargam below (lower left),
  • Calcite, Galena and Halite- cleavage in three directions, see the diargam below (lower right).
  • If a mineral breaks along irregular rough surfaces it shows fracture. Quartz shows a special type of fracture called concoidal (shell-like) fracture.
  • Hardness
  • Hardness- The ability of one mineral to scratch another. The softer mineral gets scratched. You test a mineral's hardness by scratching the unknown mineral with an object of known hardness. Moh's Scale of Hardness is used to rate the hardness of a mineral. The chart below shows the ten minerals that make up the hardness scale and some common materials with their hardness to test unknown minerals. One on the scale is the softest and ten is the hardest.
  • To find the hardness of a mineral you first have to find out what it can scratch and what can scratch it. For example, if a mineral can scratch glass but can't scratch a streak plate, the mineral has a hardness of 6 on the Moh's Hardness Scale.
  • Color
  • Color- The most easily observed property, but usually the least useful. A mineral's color can be changed by the impurities that are found in the mineral.
  • Luster
  • Luster- The way light is reflected from a newly exposed surface. Described as either metallic or nonmetallic. Some examples of minerals with metallic luster are pyrite, galena and magnetite. Some examples of minerals with nonmetallic luster are calcite, quartz and feldspar. Nonmetallic luster can also be described as glassy, pearly, waxy and earthy (dull).
  • Special Properties
  • Acid test- This test is performed by dropping weak hydrochloric acid on the mineral. If it reacts (fizzes) then the mineral is calcite. This test will also help to identify the rocks limestone and marble, because calcite is the principal mineral in both.
  • Magnet test- If there is a magnetic attraction between your mineral and a metal object, then the mineral has a high iron content. The mineral magnetite will attract metal objects.
  • Igneous RocksIgneous rocks are classified by their composition and textureIgneous rocks are produced by the cooling of magma or lava.
  • Fast cooling = extrusive, small crystals. Slow cooling = intrusive, larger crystals
  • Extrusive small grains, glassy, air holes present (obsidian, pumice, basalt)Intrusive large grained, graniteMetamorphic formed by heat and pressureMetamorphic classified as foliated (banded) or non foliated
  • Foliated rocks are slate,
  • schist, gneiss
  • Non-foliated include
  • marble and quartzite Limestone morphs into marble. Sandstone morphs into quartziteSedimentary
  • Sedimentary rocks are formed from rock fragments, organic material, or chemical precipitation
  • Sedimentary are classified as clastic, organic, and chemical
  • Limestone is formed both chemically and organically
  • Sedimentary are found in flat layers or strata. Fossils are found in these layers
  • Clastic rocks are made of fragments –conglomerate, sandstone, shaleDestructive Geology
  • Chemical weathering occurs mainly in warm, humid climates
  • Weathering can occur as either a mechanical or chemical processErosion is the process of materials being transported by moving water, ice, wind, or gravityStreams and moving water are the major agents of erosionDeposition is the dropping or settling out of sedimentsHigh erosion= high relief areas, high deposition= low relief areasLarge particles settle out first, sediment size from largest to smallest- sand, silt, clayAs particle size increases, permeability increases (ability to hold water).
  • Permeability is the ability of a material to drain
  • Porosity is the amount of pore space in a rock or sediment
  • Different grain sizes and packing arrangements result in different porosity values.  Top: individual pore spaces decrease in size with decreasing grain size. Bottom: porosity varies with packing (arrangement) of grains.
  • Soil evolution starts with the weathering of bedrock Organic material must be present in order to have soil. (humus)Soil profiles consist of 3 horizons: O topsoil (humus) most evolved, A less humus, leaching of minerals from A, and B weathered rock C These layers are on top of bedrockGroundwater layers from the surface down would include zone of aeration, water table, and zone of saturationAn aquifer is a layer of rock that transports groundwater freely
  • A spring is an area where the water table reaches land’s surface
  • The watersheds of Virginia are the Sounds of North Carolina, the Chesapeake Bay, and the Atlantic Ocean.The Coastal Plain is the flattest area underlain by all the types of sediments produced by the erosion of the Appalachian MountainsPiedmont is underlain by igneous and metamorphic rocks produced by ancient volcanoes. Separated by the fall line from the Coastal Plain.Blue Ridge Mountains are oldest in the state they were produced by converging plates.Valley and Ridge long parallel ridges composed of folded and faulted rocks that occurred during the collision of Africa and North America during the Paleozoic.
  • Karst Topography and fossils are abundant
  • Karst topography has caves and sinkholes produced by acidic groundwater dissolving limestoneAppalachian underlain by sedimentary rocks. Coal resources are found here. Fossils present.Virginia resources include limestone, coal and gravelRenewable resources can be replaced by nature at a rate at which they are used. Includes vegetation, water, and soilNonrenewable resources are renewed very slowly or not at all. Includes coal, oil, and mineralsThe Earth’s water supply is renewable but also finiteA fossil is the remains, impressions, or just the evidence of life preserved in rockVirginia’s fossils are mostly marine and are from all eras in historyThe Principle of Superposition states that the oldest rocks are found on the bottom of strata and the youngest are found on topThe Principle of Cross-cutting relationships state that an igneous intrusion is younger than the layers it cuts acrossFossils, Superposition, and Cross-cutting relationships are used to determine relative agesRelative ages are placing events in sequence without assigning exact numerical agesAbsolute age gives numerical age to an eventRadioactive decay or half-life is used to determine the absolute age of rocksRadioactive isotope Daughter isotope Half-life (Myrs) ApplicationsCarbon 14 Nitrogen 140.0057 Formerly living material less than 30,000 yoUranium 235 Lead 207713 Lunar samples, meteorites, pre-Cambrian rocksPotassium 40 Argon 40 1300 Ocean floor basalts, lava flows, some sediment.Uranium 238 Lead 2064510 Lunar samples, meteorites, pre-Cambrian rocksRubidium 87 Strontium 8747,000 Very old rocks, similar to Uranium
  • Uranium dating is used to find the ages of the oldest rocks.
  • Carbon-14 is used to find the ages of human artifacts.
  • The Earth is about 4.6 billion years oldEnough is enough………..
  • Remember:
  • Make sure you understand the question
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  • Slash the trash, get rid of the ones you know are not the answer
  • When you are left with 2 answers, use the one that was your first choice
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