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Unformatted text preview: Introduction -How to estimate: Recurrence interval: average number of years between disasters Probability of a natural disaster: 1/recurrence interval Potential financial risk from a natural disaster: the probability of a disaster multiplied by the expected financial loss -Understand that geological processes that cause disasters is the first step to mitigating their effects For example: knowing that faults cause earthquakes helps to identify potential areas of quakes and helps to determine dates of past quakes Earth Materials Isotopes- have the same number of protons but a different number of neutrons Some isotopes are radioactive (they decay), can be used to get timing and ages of events Mineral- natural, inorganic, have a specific chemical composition, and possess a crystalline structure -Quartz and feldspar hard, strong silicate minerals Primary constituents of the rock granite -Clay weak silicate mineral that is found as very small platy particles. Like mud Primary constituent of the rock shale -Calcite (calcium carbonate) weak, soft (you can scratch it) Makes up limestone and marble Rock- made up of minerals Igneous rocks form when magma solidifies o Magma molten rock, actually a liquid (lava is magma on the surface of the Earth) o i.e. Basalt Sedimentary rocks made up pieces and parts of weathered rock (sediment) o i.e. conglomerate Metamorphic rocks formed when u squeeze or heat up a rock o Occur somewhere deep where there are pressures and higher temperatures o i.e. when mud (a sediment) is buried it becomes shale which is pressured deeply with high heat to become slate which when pressured further becomes gneiss Dating and the Geologic Time Scale Relative dating- establishes the order or sequence of events -Principles of relative dating Law of original horizontality- sediments are deposited in horizontal layers Law of lateral continuity- unless something happens, those layers continue horizontally forever Law of superposition- younger layers are deposited on top of older layers Law of inclusions- inclusions are older then the rock that contains them Law of cross-cutting relationships- geologic events that cut across pre-existing rocks are younger than the rocks they cut o Most typically were looking at faults, volcanic events, and erosion Absolute dating- gives a numerical time or date half-life : time it takes half of parent to decay to daughter constant rate of radioactive decay...
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- Spring '08