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 earth’s 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 dominant—sparse 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 impact—river 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 earth’s 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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