GeologyFinal - Definition of a glacier o Large mass of...

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Unformatted text preview: Definition of a glacier o Large mass of slowly moving ice o Ice sheets are glaciers that cover large areas of continents o Form above the snowline, confined to high altitudes o Higher part of glacier gets thicker with snow each year o Ice flows downhill under its own weight, combination of plastic deformation, some melting at the base o Abalation- balance between accumulation of snow and melting snow, if net accumulation is larger than net abalation the glacier grows and pushes its front downhill. Greenhouse gases o Keep earths temp warm o Increased CO2 in last 100 years from burning coal, natural gas, and petroleum o Clearing forests helps increase CO2 o Long term effect- greenhouse gases remain in atmosphere for decades Location of deserts and causes of aridity o Deserts are defined by a low amount of precipitation and cover 19% of land surface o Deserts are found in both cold and hot environments o Mechanical weathering is dominantsparse vegetation o Water is the main weathering agent with wind o Nile, uadi, arroyos Beach erosion o Sloping portion of the coast composed of sediments and moved by waves, tides, and currents o Sediment comes from rivers and wave erosion on cliffs o Human impactriver damming reduces sediment supply- the dam stops water and blocks sediment Types of fossil fuels o Coal is solid o Petroleum is liquid Formed in shallow basins within continents, lagoons, or continental shelves Mainly composed of fossil plankton and organic material Natural gas usually found on top of petroleum reservoirs. o Asphalt is a thick petroleum Petroleum because of plate tectonics Petroleum forms traps with folds and faults where petroleum and gas are captured and preserved until we get them out through wells. Definition of mineral resources o To have an economic value, a mineral resource must be concentrated and easily extractable o Ore is a naturally occurring material from which an economically valuable mineral can be extracted o Grade of an ore: concentration of material o Low grade is less valuable because of high concentration costs Geologic time scale and main milestones of life evolution o 4.6 billion years old o Oldest rock=3.9 billion years old o First abundant life= 570 million years o Largest mass extinction=250 million years o Extinction of dinosaurs=65 million o First humans= 2 million years o Precambrian- 85% of earths history o Precambrian Internal heat production was 4-6 times higher than today Plate tectonics more active Rate of volcanism, subduction and plate production much higher than today o Phanerozoic- visible life, started 570 million years ago, covers most of the evolution of life Paleozoic- era of trilobites Mesozoic- era of reptiles Cenozoic- right now, era of mammals Relative geologic time and laws of stratigraphy o Relative time tells me that A is younger/older than B o Principles: Uniformitarianism- physical processes we observe...
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