Midterm Study Guide
Midterm Study Guide GEOL 306
Popular in Volcanoes and Earthquakes
Popular in Geology
This 7 page Study Guide was uploaded by Maddie Evans on Wednesday October 28, 2015. The Study Guide belongs to GEOL 306 at University of Oregon taught by Dr. Bindeman in Summer 2015. Since its upload, it has received 127 views. For similar materials see Volcanoes and Earthquakes in Geology at University of Oregon.
Reviews for Midterm Study Guide
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: 10/28/15
Geology Midterm Study Guide Lecture and Discussion Notes General Information gt The Earth is everchanging and is never in a state of sameness gt Some structures like the Grand Canyon and Yellowstone would still be there 200 million years ago as the Earth is nearly 6 billion years old gt The continents are never in xed locations and always moving gt Plates have the potential to collide creating mountains or larger continents as well as split apart and create seas and oceans gt The movement of plates can cause climate changes volcanoes mountains earthquakes extinctions fossil distribution General Information about Plate Tectonics gt The globe is divided up into an in nite number of plates that which the continents and land masses sit upon gt The ocean is getting simultaneously created and consumed by other plates gt Mountain belts are created by continental land masses plates that land masses sit on colliding into each other and pushing matter upwards gt The motion from plates can cause earthquakes and volcanoes Theory of Plate Tectonics gt Earthquakes tend to occur at plate boundaries where plates are shifting and creating tension and friction on one another they can be divergent or transforming gt Volcanoes tend to occur at plate margins where heat is excessively produced gt Plates are always moving hence the almost constant earthquake activity gt The evolution of ora and fauna could be due to the plates moving as they grow but separate from each other causing changes in species that resemble one another at plate bounda es Three Theories of Tectonics gt Continental drift hypothesis 19121960 5 gt Fixed land masses before 1960 s gt Modern plate tectonics 1960current 1912 Continental Drift Theory gt gt gt Matching Continental Plate Boundaries if one was to cut up continents and paste them together as puzzle pieces they would match up almost perfectly aside from slight erosion Similarities of oras and faunas animal and plant species are similar at continental boundaries see puzzle analogy above Alternative Explanations 0 Ice or wood rafting animalsplants could have been transferred from one land to another by raft 0 Land bridges small portions of land may have been connected to continents and allowing ora and fauna to relocate Ocean Floor Discoveries gt gt gt gt Central rift valleys indicating tension between plates Central rift valley having high heat ow and having volcanism Deep ocean trenches are usually the deepest parts of the ocean and are usually long and narrow Unable to determine ocean ooding older than 200 million years by drilling and dredging Paleomagnetism gt gt gt Magnetic eld changes with time Magnetic pole and rotational pole are averaged to change over thousands of years Magnetic reversal happens roughly every 5 to 1 million years Switching North and South poles Polar quotWanderingquot gt gt gt From 1950 to 1960 The magnetic eld in young lavas in Eurasia pointed toward our North pole but in older lavas would point to other locations or South pole This caused poles to quotwanderquot or assume continental movement Spreading and Subduction gt gt VVV Explained by Henry Hess from Princeton When oceanic crust is slowly pulled apart from the middle magma and molten rock seeps in between the cracks and fractures to create the new oceanic crust Convection cells move downward and bring the plate down and the sea oor is gradually deepened Ocean oor always young because always renewed DivergentExtensional spreading ConvergentCompressional Subduction gt Slip Transform Plate Boundaries gt Earth s surface area is never increasing only renewing gt Spreading and subduction are both faults Geometry and Kinematics of Plate Motion gt Poles of rotation are when the plate s angular velocity remains the same but linear velocity increases away from the pole of rotation gt Triple junctions are where convergent divergent or transform plate boundaries meet in various combinations to accommodate movements on a sphere s surface 0 The Earth could not only be made up of one type of faulting has to adjust to the crust and area gt The Atlantic Ocean is a largely passive continental margin gt The Paci c Ocean including the Ring of Fire is an active continental margin gt The Indian Ocean is both passive and active Subduction Zones gt Three kinds of convergent margins o Oceanic to continental ocean crust meeting continental crust o Oceanic to Oceanic ocean crust meeting ocean crust 0 Continental to Continental continental crust meeting continental crust gt The density of the subducting plate will always be greater than the underlying plate 0 Asthenosphere 325 gcm3 0 Continental Lithosphere 310 gcm3 0 Old Oceanic Lithosphere 328 gcm3 0 Young Oceanic Lithosphere 326 gcm3 gt Continental Crust is rarely subducted Volcanoes and Earthduakes at Converdent Boundaries gt Volcanism happens when the mantle above the subducting plate melts due to dewatering gt Seismicity is when there is friction between the plates that cause earthquakes Transform Plate Boundaries gt No new crust is created gt Usually occurring in ocean basins gt The act of sliding back and forth with no volcanism gt gt Creates the strongest earthquakes with friction San Andreas Fault 0 Has power to offset river deltas o In the future Baja California would be located where Alaska currently sits Plate Tectonics and Volcanism gt gt gt gt gt Melting of the mantle 0 Partial melting usually occurs Melting in midocean ridges and hotspots common and aids in spreading Peridotie is the most abundant rock on Earth and most other planets Makes up the mantle and it s core Not seen often on surface or upper crust Plumes and Hot Spots gt gt gt gt Has a mushroom appearance with a thick and wide head and narrow tail The plume materials at the shallower depths are partially molten Seen on the surface as a hot spot Mantle plumes are narrow areas of hot plastic rock that rise through the mantle Density and Viscosity gt gt Oil is less dense than water and will oat Oil is more viscous than water and doesn t ow as easily Thermal Expansion gt When something is heated it expands and becomes less dense and less viscous Hot Spots gt gt gt gt gt Rocks gt gt Credited with ability to form oceanic islands Appear to move but always staying still and moving plates slide over and form islands Hawaiian Islands Leaving tracks on moving plates Can produce medium to high volumes of basaltic magma Large volumes in the rst 1 2 million years but gets weaker with younger islands Granite Sand Sandstone Quartzite Types of rocks 0 Igneous granite basalt gabbro V VVVV o Sedimentary sandstones limestone o Metamorphic schist gneiss Si02 silica concentration in rock and magma determines the chemical and physical properties of rocks color mineral composition density viscosity etc Peridotite makes up most of the mantle Basalt makes up most of the oceanic crust Andesite makes up most of the continental margins Rhyolite and granite make up most of the continents ldneous Rocks gt VVV Volcanic erupted on the surface 0 Containing glass and vesicles 0 Usually negrained o Effusive lava o Pyroclastic volcanic ash scoria pumice bombs Plutonic cooled and crystallized at depth 0 Contains larger crystals Magma is melted crystals and gas Lava is magma that has lost its gas lgneous rock is solid that was made from cooled and fully crystallized plutonic or partially crystallized volcanic magma Volcanism and Plate Tectonics gt gt gt 5 types of volcanism Midocean ridges basaltic almost completely underwater less viscous shield volcanoes quite effusive eruptions Hot spots when under continents form huge calderas and rhyolitic eruptions Subduction zones above water level viscous explosive pyroclastic eruptions and form island arcs lntraplate volcanism mostly basalt more explosive Magmatism of continental collision zones mostly granite little basalt little volcanism Textbook Notes Chapter 2 gt gt gt Distinction between mantle and crust based on rock composition Lithosphere the stiff and rigid outer rind of Earth containing tectonic plates Asthenosphere has inner hotter and more easily deformed rock VVV Elevation difference between continental and oceanic crusts is explained by isostacy buoyancy Earth s plates move up to 11 cm per year Eruptions occurring daily along oceanic ridge systems Spreading centers in continents pull apart at much slower rates and don t usually form plate boundaries High Cascades volcanoes are an example of Convergent boundaries subduction where the oceanic crust is diving underneath the continental crust San Andreas Fault has moved California at least 350 kilometers so far Transform faults generate the most earthquake and all have potential to be catastrophic 1 to 2 dozen rigid lithosphere plates make up the outer 60 to 200 kilometers of Earth Continenttocontinent collision is where the tallest mountains are formed and largest earthquakes Chapter 6 gt gt Melting temperature controlling when a rock becomes magma Magma chambers are large masses of molten magma that rise through Earth s crust and usually erupt to form volcanoes Rhyolitic magma ows extremely thick and stiff Fissure is when a crack opens in the oor and erupts a large basalt ow Pahoehoe lava is very easy owing Aa lava is blocky and hard owing Volcanic Explosivity lndex VEI quanti es the eruption size volume and violence Phreatic eruptions are violent steamdriven explosions generated by vaporization of shallow water in the ground Strombolian eruption is fed by magma that interacts with groundwater or seawater Vulcanian eruptions include ash falls that dominate Mauna Loa is Hawaii s largest volcano that has erupted 33 times since 1843 Etna s eruptions feature occasional violent episodes Cinder cones are basalt but characterized by small size low viscosity steep sides and moderate volatile content Stratovolcanoes have moderate volume and size moderate viscosity and slope and moderate volatile content The tectonic environment dictates the volcano distribution type composition and behavior gt Volcanoes that are not near plate boundaries are generally situated over hotspots
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'