MOD A - Nature of Science.docx

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Earth and Ocean Sciences
EOSC 116
Louise Longridge

Key Concepts Science  Branch of knowledge dealing with material phenomena and based on observation, experiment, and induction; systematic and formulated knowledge; and skillful technique Earth System Science  Views the earth as a working system (each part has an impact/effect on the other)  System includes atmosphere, oceans, tectonic plates, processes deep in the earth, and life Monty Python and the Holy Grail (Witch and Duck Test)  Retarded science and horrible logic does not an experiment make  The witch claims she is not a witch, people burn witches, but they also burn wood, so witches must be made of wood  Wood floats, and so do ducks, therefore, the witch must weigh the same as a duck to be made of wood to be burnt… dafuq The Scientific Method  Science: method of observing and interpreting the physical universe o Every event must have a physical explanation  Process o (1) Observation: detailed and clear o (2) Hypothesis: provisional theory to explain the observations o (3) Test hypothesis: self-explanatory o (4) Repeated testing: raises the hypothesis to the level of a theory  found “true” o (5) If a theory is always observed to happen, it may become a law o (6) Continual re-examination: test and reinterpret Key Geological Concepts The Earth’s Interior (From Exterior to Interior)  Lithosphere: continental and oceanic crust and the uppermost part of the mantle o Fractured into plates o Continental crust is richer in minerals containing silica o Oceanic crust has more iron  Asthenosphere: upper mantle o Acts as a soft, lubricating layer over which the crustal lithospheric plates move  Mantle: relatively hot, viscous layer o In continual motion (hot mantle rises from the depth and cooler upper mantle sinks)  motion known as convection currents  helps move lithospheric plates  Outer core: liquid  Inner core: solid with a metallic composition Theory of Plate Tectonics  Known as the Grand Unifying Theory  Explains how the plates and continents are pushed and pulled Types of Plate Boundaries  Geological activity that occurs at plate boundaries: plate formation, earthquakes, volcanic activity, mountain building Divergent (Constructive) Boundaries  Plates move away from each other and new crust is constructed  Can form within a continental plate to form a new ocean basin  Ex. Mid-Atlantic Ridge Convergent (Destructive) Plate Boundaries  Plates move toward each other and collide (Himalayas)  When two oceanic plates collide or an oceanic plate collides with a continental plate, one is subducted below the other o When two oceanic plates collide, volcanic islands form above the subduction zone o Oceanic plate always subducted below the continental plate (denser) o Mountain ranges that run along the edge of the continent will form (ex. Cascades) Transform Plate Boundaries  Plates move past each other without the creation or significant destruction of crustal material  Ex. San Andreas Fault Rocks are Composed of Minerals  Rocks: tons of minerals piled up on each other (aggregates of minerals)  Mineral: naturally occurring, crystalline, inorganic substance with an ordered arrangement of atoms The Three-Fold Rock Classification System  Igneous o Crystallize (solidification) from a molten material (AKA a melt) to form a rock composed of interlocking crystals o Melt: generated from the “partial melting” of mantle material or rocks deep in the crust  Volcanic/extrusive: if cooled at the surface of the Earth  Plutonic/intrusive: if cooled and solidified inside Earth  Eventually exposed to the surface via weathering and erosion  Cools slowly  possesses larger crystals than extrusive rocks  Metamorphic Rocks o Formed by altering pre-existing rocks via metamorphism o Transform rocks with heat, pressure, and/or liquid that percolates (filters through porous surface) through the subsurface  Sedimentary o Physical erosion and weathering or another rock  forms clastic (composed of broken rocks) sedimentary rock (ex. Sandstone, siltstone, mudstone)  Composed of fragments/grains of rocks that were being eroded o Chemical precipitation to form an evaporite  Forms when water evaporates to form layers of salt (ex. Commercially mined salt) o Biological precipitation of minerals  Coral reefs, sediments composed of shells, clams, or the skeletons of microscopic plankton (ex. Limestone), and deposition of plant material (ex. Peat and coal) o Sediments transformed into rock via diagenesis or lithification (physically cements the sedimentary grains together) o Involves heat, pressure, and percolating fluids The Rock Cycle  How rocks can be transformed by various Earth processes into any other rock in the 3-fold classification Geological Deep Time  Helps us understand continent drift, mountain formation, erosion, dinosaur evolution/extinction  If you compress Earth’s 4.5 billion year history into one calendar year… o Jan 1: Earth forms o November 18: first creatures with shells evolve o December 25: dinosaurs go extinct o Dec 31, 11:59:57: humans An Introduction to Geological Time The Age of the Earth: Early Estimates  James Ussher: used the Bible to estimate the age of earth  6000 years old  George Louis De Buffon: thought the earth solidified from a molten state  tested how long it took iron to cool to room temperature  75,000 years old Stratigraphy  Study of rock strata (layers of sedimentary rock), layer sequence  tells geologic history and relative ages of a region  Each sedimentary layer represents an instant in time  Errors o Cannot assume a constant rate of deposition of sediment o Erosion o Deposition of large volumes of sediment causes compaction (squashing) of the sedimentary pile  underestimate of total amount of sediment Relative Dating  Technique that relies on Laws of Stratigraphy (way in which strata are laid down over time)  Very reliable (used with radioactive dating) Principles of Stratigraphy  Nicolas Steno  The Principle of Original Horizontality o Rocks that are currently folded or tiled were once deposited as flat horizontal layers  Principle of Superposition o In a stack of sedimentary rocks, the layers (beds) at the bottom will be the oldest  Biostratigraphy and the Principle of Faunal Succession o Biostratigraphy: based on the principles of stratigraphy, relates to the passage of geological time o Leo da Vinci: understood that fossils were the remains of once living organisms o William Smith: recognized the importance of ^ in stratigraphy o Smith’s Principle of Faunal Succession: different types of fossil can be found in a regular order through sedimentary rock layers
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