GEOL204 Final Key Concepts 05 13 2015 Please Review the Exam Review sheets for Midterm Exams 1 2 especially The nature of Science as a field of study Nature of Science Hypothetico Deductive method Role of argument of evidence of uncertainty Define If you were wrong how would you know it The hypothesis stands till it is falsified disproved Argument a connected series of statements intended to establish a proposition consisting of one or more premises which support the conclusion Evidence relies not on argument but independent evidence empirical Physical Evidence and Reasoned Logic PEARL Uncertainty there are limitations of observations for example the accuracy and resolution of instruments so we will not always find the same exact value Hypotheses null hypotheses theories especially scientific theories speculations Falsification parsimony consilience Scientific publications Peer review Hypothesis is NOT an educated guess but rather a formal statement of a pattern that appears to exist in a set of observations Null Hypothesis represents a form of the hypothesis that must be rejected before we even accept a phenomenon exists Theory most simply an explanation Scientific theory is more specifically a comprehensive framework for describing explaining and making falsifiable predictions about related sets of phenomena based on rigorous observation experimentation and logic Falsification testing to see if it s wrong Principle of parsimony Other things being equal choose the claim that is the simplest explanation for the phenomenon Principle of consilience Other things being equal choose the claim that doesn t conflict with well established knowledge Peer review hallmark of scientific analysis edited and judged to see if conclusions are justifiable etc How the geologic and fossil record is formed Sedimentology Earth structure Core mantle crust Lithosphere asthenosphere Core metal Solid crystalline inner core Liquid outer core Mantle rocky but denser and more compact rock than any found on the surface Lithosphere also rocky Contains the uppermost layer of the mantle and the brittle crust Plate tectonics discovery and role in the Earth System Divergent boundaries transform boundaries convergent boundaries Plate Tectonics models of continental drift and seafloor spreading were combined by John Tuzo Wilson and colleagues to form plate tectonics New material generated at divergent boundaries plates slide away from each other mid ocean ridges in sea rift valleys on land Plates slide past each other at transform boundaries Plates come together at convergent boundaries whose type depends on whether or not one of the plates is oceanic crust Rock Cycle and rock classification igneous metamorphic sedimentary Rock Cycle Sedimentary Metamorphic Magma Igneous Sedimentary repeats Igneous Formed by the cooling of molten material Igneous formed by lava cooling on the surface are volcanic rocks also called extrusive because they extrude onto the surface Igneous rocks formed by magma cooling at depth are plutonic rocks also called intrusive because they intrude into previously existing rocks Metamorphic Formed by recrystallization of previously existing rocks due to intense heat and or pressure i e they are baked and or squashed Will often contain unusual minerals that only form at incredible temperatures and or pressures Sedimentary Formed from transported fragments of previously existing rocks Bits of previous rock and or organic matter are called sediment Environments of Erosion vs Environments of Deposition Erosion which breaks rocks down into particles or ions which can then be Deposited forming new layers of rock and removing some material out of the atmosphere hydrosphere or biosphere and adding it to the lithosphere Factors controlling the type of sedimentary rocks produced energy of environment higher the energy the larger the size of sediment moved if energy is too high then erosion can occur instead of deposition silicate sediment most igneous or metamorphic rocks carbonate sediment sea shells carbonate mud formed in warm salty water biogenic input broken parts of sea shells or algal skeletons or coral agent of transport wind deposit uncover redeposit flowing water waves back and forth produces ripples and cross beds glaciers simultaneous deposit of sediment of all different sizes sedimentary structures cross beds horizontal units that are internally composed of inclined layers ripple marks mudcracks form from drying of already deposited sediment anoxic laminations areas of water that are depleted of dissolved oxygen oxygenated bioturbation is the reworking of soils and sediments by animals or plants types of paleoenvironments Sea level changes over time sea level is much lower than before Lithification and diagenesis compaction cementation recrystallization Lithification how sedimentary strata are deposited but it doesn t explain how the loose sediment becomes a cohesive solid aka a rock Compaction as new layers are deposited over older ones the lower layers get squished squeezing out ground water in between the sedimentary particles and causing the stratum to compact In some minerals clays for instance this process may be enough to strongly bind together the sedimentary grains thus lithifying it Cementation minerals in the pore water can precipitate between grains of sediment to bind them together Recrystallization crystals of some minerals esp some carbonates can grow and join together at the pressure and temperature conditions present in burial Fossils and Fossilization Definition of body and trace fossils Body Fossils Specimens which were actually once part of a living thing bones teeth skin shell leaves trunk pollen egg etc Trace fossils those that are marks in the sediment produced by the activities of living thing Examples of trace fossils types of behaviors represented Fossilization potential hard parts vs firm parts vs soft parts lifestyle in marine realm planktonic vs nektonic vs benthic infaunal vs epifaunal number and integration of parts Taphonomy necrolysis biostratinomy rate and medium of burial autochthonous vs allochthonous diagenesis unaltered recrystallized permineralized carbonized replacement mold case Planktonic organisms float above the seafloor normally in the shallow layers of the water regardless of how deep it is Since they don t care about the conditions underneath some of them will settle down onto depositional environments when they die but some might not Nektonic