geology midterm 3

geology midterm 3 - Emsellem 1 Geology study guide...

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Emsellem 1 Geology study guide Midterm #3 Chapters 14, 19, 11 Chapter 14 Earth’s resources Earth resources: energy, mineral, water Fossil fuels = oil, gas, coal, oil shales, tar sands, gas hydrates o Non –renewable energy resource (created by processes that take long spans of time to form) o Combustible materials derived from organisms that lived in the past and stored solar energy o Formed as the result of the burial and subsequent transformation of organic material Gas hydrates: chemical compound consisting of a methane molecule surrounded by a cage- like arrangement of water molecules, under the sea floor o 1. Potential energy source because of the great volume of methane Crystalline solid Similar to ice because its building blocks consist of a gas molecule surrounded by a cage of water molecules but is stabilized o Form: when anaerobic bacteria eat organic matter such as dead plankton that have been incorporated in the sea floor, when the bacteria digest the organic matter they produce methane as a byproduct Methane then bubbles into the seawater that fills the pore spaces in the sediments Methane dissolves in water and produces gas hydrate molecules only at a narrow range of pressure and temperature – depths greater than 300 m (can occur at shallower depths at colder or polar latitudes) THEREFORE changes in pressure and temperature is a disaster, along with sea-level fluctuations caused by glaciers because its breaks down and the methane is released into the atmosphere (because hydrate is a gas concentrator) Break down of 1 unit of methane hydrate produces 160 volumes of gas World amount of methane gas hydrates is about 2x the amount of carbon held in all fossil fuels on earth Stable at pressures and temperatures that occur in ocean-floor sediment at depths greater than 500 m, there the temperature is above those for ice stability o Form as cement in the pore spaces of sediment as well as in layers and nodules of pure hydrate: capacity to fill sediment pore space therefore reducing permeability = seal for gas traps Formation is influenced by porosity, permeability and degree of lithification o Huge reservoirs off the east coast a little off shore o 2 . Effects of gas hydrates: atmosphereic methane may influence the global climate by modifying the global greenhouse Methane is 20x as effective as a greenhouse gas as carbon dioxide o 3. effects sediment strength :
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Emsellem 2 Because gas hydrates cement sediment its formation and breakdown may influence the occurrence and location of submarine landslides (which release methane gas into the atmosphere and affect climate) Occurs when sea level changes which alters the water pressure: initiates a landslide by converting the hydrate to gas + water = weakening of sediment = rise in pore pressure Temperature stability is between 0 and 20 degrees Celsius Occur at continental shelves o Yes it is an energy resource but it is very dangerous
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geology midterm 3 - Emsellem 1 Geology study guide...

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