Study Guide for Exam 1
Study Guide for Exam 1 Geo 102
Popular in Principles of Geology
Popular in Geology
This 14 page Study Guide was uploaded by Marley Thomas on Tuesday September 8, 2015. The Study Guide belongs to Geo 102 at Illinois State University taught by Bill Shields in Fall 2015. Since its upload, it has received 102 views. For similar materials see Principles of Geology in Geology at Illinois State University.
Reviews for Study Guide for Exam 1
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
Date Created: 09/08/15
Notes for first exam Minerals Isotopes elements with different numbers of neutrons in the nucleus Ions atoms with excess positive or negative charge gain or loss of electrons from the outermost shell Ions dissolved in water will combine to form compounds Cations positive charge lose electrons Ca Anions negative charge gain electrons C03 39 Compounds combination of atoms of one or more elements in a specific ratio Types of Bonds 1 Van der Waals weakest bond weak attraction Graphite 2 Ionic transfer of electrons between cations and anions Sodium Chloride salt NaCl 3 Covalent strongest bond electrons are shared between atoms Oxygen 02 Most Common Elements the most common elements on our planet by weight are Oxygen and Silicon They combine and become part of the largest family of minerals the SILICATES 1 Oxygen 47 2 Silicon 28 Five Requirements to be a mineral 1 Naturally formed Solid Formed by inorganic processes Specific chemical composition Characteristic crystal structure 9593 Properties of Minerals 1 Crystal form The shape of an individual mineral crystal and is a re ection of the internal arrangements of atoms 2 Habit The shape of a single or group of mineral crystals 3 Cleavage a smooth break producing what appears to be a at crystal face This break is along a plane of weakness in the crystals atomic structure 4 Luster a description of the way light interacts with the surface of a crystal For your class we will define a luster as being metallic or nonmetallic 5 Color Not good for identifying minerals Trace amounts of impurities can give a mineral different colors 6 Streak The color of the mineral in its powdered form This is a true indication of a minerals color Density The weight per volume of a mineral 8 Hardness The resistance of a mineral to be scratched The stronger the bonds the harder the mineral gt1 Mohs Hardness Scale unit less this scale is used to determine the RELATIVE hardness of minerals helps in their identification The scale is numbered 110 With small numbers being soft minerals and large numbers being hard minerals Igneous Rocks Rock a coherent naturally occurring solid consisting of an aggregate of one or more minerals or a mass of natural glass or organic matter Basic Rock Classi cations OIgneous Sedimentary Metamorphic Igneous Rocks a rock that forms when hot molten rock magma or lava cools and freezes solid Two types of igneous rocks Plutonic cools underground Volcanic cools above ground Factors controlling Melting 1 Temperature Melt at 8000C and IZOOOC Source of heat radioactive decay Partial Melting Some minerals melt at a lower temperature than others Geothermal Gradient the rate at which temperature increases with depth in the Earth 2 Pressure as pressure increases melting temperature increases Lowering pressure causes melting in divergent margins 3 Water content as water content increases melting temperature decreases Water in rocks causes melting in convergent margins Bowen s Reaction Series There in an order in which different minerals crystallize Usually the dark coloredmafic minerals crystallize first as a magma freezes Likewise they are the last to melt as a rock heats up Types of Molten Material 1 Magma molten material below the Earth39s surface 2 Lava molten material above the Earth39s surface Magma Chemistry Molten material can consist of liquid rock mineral grains and gases H20 C02 SOZ Silicon and oxygen SiOZ make up the majority of a magma 45 SiO2 quotlowquot silica content 75 SiO2 quothighquot silica content OMafic low SiOz high iron and magnesium 0FelsicSilicic high SiOz low iron and magnesium Magma Viscosity Viscosity resistance to ow honey high viscosity water low viscosity Viscosity increases as silica content increases Igneous Rock Types Intrusive plutonic rock cools and solidifies below the Earth39s surface Extrusive volcanic rock cools and solidifies above the Earth39s surface Textures of Igneous Rocks Texture overall appearance related to size shape and arrangement of minerals Texture is related to cooling history of an igneous rock not its chemistry There are two main terms for igneous rock textures Phaneritic Slow cooling that results in crystals big enough to see with the unaided eye Aphanitic Rapid cooling that results in crystals too see with the unaided eye Two special Aphanitic textures are Vesicular this rock contains small cavities left as gas bubbles froze Glassy this rock looks like dark brown or black glass and is created when the lava cools so fast the almost no crystals form Volcanoes and Volcanism Volcano a vent through which magma solid rock debris and gases are ejected Classified by the type of eruption Largely a function of viscosity and dissolved gas content of the magma Viscosity the resistance of a liquid to ow MagmaLava With a high silica content have a high viscosity they are thick not runny Felsicsilicic melt has a high viscosity 1 Non explosive low viscosity ows easily low silica content mafic basaltic magmalava Associated Landforms 1 Shield Volcanoes broad at volcano With gently sloping sides built of successive lava ows 2 Basalt Plateaus ood basalts lava emerges from elongate fractures or fissures and spreads Widely to create vast at lava plains sometimes covering 1039s or 10039s of thousands of square kilometers 2 Explosive high viscosity resists ow high silica content intermediate felsic andesitic or granitic magma lava Associated Landforms Composite Cones large nearly symmetrical built by alternating layers of lavas and pyroclastic fragments most violent Mt Saint Helens Mt Rainier Located at converging oceanic continental plate boundaries Crater a funnel shaped depression near the summit of a volcano Caldera a large crater usually greater than a kilometer across Pyroclastic flow hot pyroclastic material and gases Which rush down the anks of a volcano Lahar hot and cold liquid and debris Pyroclastic Rocks Tephera Bombs largest Lapilli intermediate size Ash smallest Lava types pahoehoe pronounced pahhoyhoy relatively smooth skin aa pronounced ahah rough surface jagged blocks Predicting Earthquakes Ground tilt and displacement Increases in surface temperature Monitoring earthquakes Changes in gas composition Why are some explosive while other are not Explosive volcanoes has a magma composition which is high in silica While nonexplosive volcanoes are low in silica High silica magma is thick and allows for more gases to be trapped Within them When the pressure confining the magma is released the gases evolve explosively Hazardous Volcanic Geologic Processes Tephra Fall Mixture of hot gas and fragments less dense than air Maj or Hazards of Tephra Fall 1Impacts 2Buria1 of structures 3Suspension of abrasive aerosols Pyroclastic Flows Avalanches of hot dry volcanic rock fragments and gases Denser than air 600 15000 F 0 Up to 200 mph 0 Tends to channel into valleys Major Pyroclastic Flows Hazards Incineration Buria1 Impacts by rock or ying material 39EXpOSUI G to noxious gases SOX C02 Most deadly kills people Explosive Ejection 0f Ballistic Projectiles Material is projected along arced trajectories 0 Not constrained by Wind direction 0 Not dependent on eruptions Large projectiles thrown 12 mile Lateral Blasts The horizontal projection of material due to pressure release Lava Flows Flow controlled by topography 0 Destructive but not life threatening 0 Speed related to slope and viscosity Lahars Rapid ow of sediment rock and water 0 Channelized Twice as fast as water Plate Tectonics The Prune Effect 1800s The molten Earth cools and contracts The crust wrinkles and crumples Mountains form Problems What about rift valleys What about shape and position of the continents The Expanding Earth 20th century radioactive decay Land masses are ripped apart Explains the continents Problems What about the mountains Continental Drift An idea before its time Alfred Wegener 1915 Processor to plate tectonics Pangaea supercontinent 200 million years ago Land fragmented and oated around Lines of Evidence for Continental Drift 1 Matching Coastlines 2 Matching Geology 3 Glacial Striations 4 Fossil Evidence Glossopteris Mesosaurus links South America and Africa during the late Paleozoic and early Mesozoic eras 5 Apparent Polar Wandering The Earth has a magnetic field This creates an invisible force field in space We can detect this field with a compass a compass needle aligns with magnetic field lines We can represent this field by an arrow that points from the north magnetic pole to the south magnetic pole through the center of the Earth Geologists discovered that rocks contain tiny magnetic mineral grains each of which acts like a tiny compass needle and points to the Earth39s magnetic poles When an igneous rock like basalt forms these needles representing the magnetization of the magnetic grains align with Earth39s field and lock into place The magnetization of recentlyformed lavas points toward the presentday magnetic poles which is near but not exactly at the geographic poles But the magnetization in older rocks does not point toward MNPWhy not One possible explanation would be that the location of the magnetic pole has changed through time an idea known as polar wandering Geologists measured magnetism in rocks of different ages in North America and constructed a polarwander path PWP to show how the pole had moved through time They did the same for rocks in Europe and found that the PWP is different from the PWP for North America This didn39t make sense So polar wandering does not occur The magnetic pole doesn39t wander The pole stays fixed and continents move So we call the trace of the pole relative to the continent and quotapparent polarwander pat quot The occurrence of apparent polarwander paths means that continental drift does occur Unifying Theory Plate Tectonics Tectonic cycle deals with the movement and interactions of the lithospheric plates The theory describing the movement of the continents and the mechanism which drives them It brings together two earlier theories continental drift and sea oor spreading This is the Unifying theory of geology and explains many of the landforms we see and processes which form them Plate Boundaries Margins Divergent Plate Boundaries l continental rift valleys 2 ocean midoceanic ridge spreading sea oor Transform Plate Boundaries Convergent Plate Boundaries Know these 1 Oceanic Continental 2 Oceanic Oceanic 3 Continental Continental Convergent when two plates move toward one another they form either a subduction zone or a continental collision This depends on the nature of the plates involved In a subduction zone the subducting plate which is normally a plate with oceanic crust moves beneath the other plate which can be made of either oceanic or continental crust During collisions between two continental plates large mountain ranges such as the Himalayas are formed Divergent linear feature that exists between two tectonic plates that are moving away from each other These areas can form in the middle of continents but eventually form ocean basins Divergent boundaries within continents initially produce rifts which produce rift valleys If the rifting process stops a failed rift results Therefore most active divergent plate boundaries are between oceanic plates and are often called oceanic rifts Transform fault a fault which runs along the boundary of a tectonic plate The relative motion of such plates is horizontal in either left or dextral right Typically some vertical motion may also exist but the principal vectors in a transform fault are oriented horizontally Weathering Three Dynamic Processes of Breaking and Removing rock 1Weathering the disintegration and decomposition of rock at or near the surface 2Erosion the movement of weather material Result of Weathering Regolith a loose layer of broken rock and mineral fragments Dissolved ions Bene ts of Weathering Creates soil Produces clay sand and gravel Produces minerals Types of Weathering Mechanical physical breakdown of rocks Chemical decomposition of rocks by chemical reactions Mechanical Weathering Make sure you know these 1Frost Wedging 2Salt Wedging 3Biological Wedging 4Unloading 5Thermal Expansion 1 Frost wedging water penetrates into cracks expands when it freezes Must have Adequate moisture Cracks in rocks 0Freezethaw cycles 2Salt wedging growth of minerals in cracks ODesert environments OWater evaporates ions in solution combine to form minerals 3 Biological wedging plant roots penetrate into cracks causing cracks to widen Must have Climate hospitable for plants Adequate moisture and temperature 4 Unloading removal of pressure of deep burial OExfoliation Domes Sheeting 5 Thermal expansion repeated daily heating and cooling of rock heat causes expansion cooling causes contraction Chemical Weathering Results in new minerals and ions in solution Water and acid are essential Types of Chemical Weathering Hydrolysis any reaction in which water participates Rain water is naturally acidic When you have environmental concern it s 10X more acidic An acid is a liquid with hs oating around in it 1Ion Exchange H replaces other cations 2Dissolution mineral completely dissolves leaving only ions in solution 30Xidation reaction in which elements gain or lose electrons example rust Factors in uencing Weathering Rates 1Rock Structures chemicalmineral composition Physical features 2Topography 3Climate the most important Wet and warm earth material weathers faster Steeper Rate of weathering is increased Cold and dry earth material weathers slower Flatter Rate of weathering is decreased Erosion transport of regolith from one place to another Corners erode faster Modes of Transport 1Water 2Wind 3Ice Transport by Water Saltation particles move downstream in short jumps Bed load material transported by saltation Suspended load material carried in water for long distances Erosion by Wind De ation Loose material can be picked up by wind Abrasion windblown sediments can quotsandblastquot rocks Transport by Wind Same processes as water saltation bed load and suspended load Erosion by Ice Plowing loose material is quotbulldozed Plucking pieces of bedrock are pried loose Abrasion pieces of rock in the ice grind against bedrock below Particle size and method of Transport Water smallest particles to small boulders Wind smallest particles to sand size Ice smallest particles to boulders as big as a house
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'