O law of uniformitarianism the physical processes

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o Law of Uniformitarianism: the physical processes that form the sedimentary rock in the past are the same as those working today and the rate at which they operate has not changed The Result - Due to slow rate of lithification, processes of forming sediment into rock and due to the number of different strata, Earth must be very old. - By the end of the 19 th century: geologists, paleontologists and biogeographers concluded Earth was several hundred million years old - 20 th century developments in radioisotopic dating has extended that age to 4.6billion years - This has all led to the formation of the geologic time scale Geologic Time Scales - Extends back over 4 billion years - Phanerozoic Eon (the time since the Cambrian period – period of abundant plant and animal life) o Cenozoic area Quaternary period Holocene Epoch Significant Moments in Earth History How species biodiversity expanded over time Anthropocene functional changes associated with human impact - biota extinction Density increases as you go down, inner core is cold Plate Tectonics - Towards the center of the earth, gets hotter Table 2.1 look at Results, what kind of topographic features are being created Magnetic Evidence - The earth’s magnetic field is going north to south, shifts and switched periodically overtime - Magma comes up, when it cools the iron molecules line up the direction of the earth – different orientations Biological Evidence for continental drift – biological dispersal - Fossil records existed simultaneously in different areas e. Rhea, Emu, Ostrich Paleoclimatic Evidence – glaciation - Glacial striations in the bedrock show the flow od ice originating from the oceans?? - Remnants – glaciers erode Stratigraphic evidence – basalt floods form volcanic sources
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- Really large single deposits, massive amount of basalt same type of sediment surrounding volcano. Changes in Distribution of Land Area - Continental drift has altered the latitudinal distribution of landmasses which has resulted in dramatic changes in regional and global climates Milankovitch Fluctuations - Natural and periodic variations in orbital geometry cause changes in the seasonal and latitudinal distribution in incoming solar radiation (cause of really warm and really cool periods) What Drives these Fluctuations - Major shifts in climate, glaciation in the past - More CO2 from the soil, feedback cycle Principle Drivers of Climate Change (Historically) Some impacts of glacial advance and retreat - Climate change far from the glaciers - Prevailing winds o Very similar to what we see around Antarctica, central storm systems, periods of dry and wet Impacts of Glaciation - Pluvial lakes – where glaciers retreat and climates became wetter. Cooler, leaving vast areas of water - Sea level changes (not climate change) o Isostatic sea-level down in one area, up in another o Eustatic sea level Glaciation and Sea Level changes: note rate of change!
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