Geology Study Guide PDF

Scientific process: Step 1: Observe a problem or research a question typically a phenomenon that is not well explained. Step 2: Form a hypothesis- something that can be proven or disproven Step 3: Experiment and hypothesis revision develop an experiment that may support or refute it Step 4:Peer...

Scientific process: Step 1: Observe a problem or research a question typically a phenomenon that is not well explained. Step 2: Form a hypothesis- something that can be proven or disproven Step 3: Experiment and hypothesis revision develop an experiment that may support or refute it Step 4:Peer review, publication, and replication. Before the hypothesis is widely accepted it must be replicated and peer reviewed Step 5: Theory development on accepted scientific idea that explains a process using the best available information Uniformitarianism: “The key to the past is the key to the present” Geologists understand ancient rocks by studying modern geological processes. (James Hutton) Nicholas Steno: Proposed that Earth’s surface could change overtime and that sandstone and shale found in layers with the oldest on the bottom and the youngest on the top Chris Lyell: Supported Hutton’s idea on uniformitarianism and proposed the Earth was 300 M years old Alfred Wagner: Proposed the plate tectonic theory Earth’s Sphere’s Geosphere: Solid body of Earth Atmosphere: The gas surrounding Hydrosphere: Water in all forms on Earth’s surface Cryosphere: Water in frozen form Biosphere: Life in all forms Reservoir: Rocks which allow petroleum resources to collect or move Transport pathways: Routes which sediments and water and other materials travel. They can travel by rivers, streams, wind, glaciers, landslides and ocean currents Earth’s Layer (outside to inside): Crust, mantle, outer core, inner core Hydrologic Cycle Evaporation: Heated bodies of water turn into vapors Transpiration: Water released into the atmosphere from plants Condensation: Water forms into clouds/fog Precipitation: When there’s too much moisture in the atmosphere, it is released through rain/sleet/snow Infiltration: When water soaks into the soil into groundwater reservoirs Runoff: Water that flows back into the body (stream, river, lake, ocean) Percolation: The formation of groundwater Earth’s 3 Main Layer Crust: Outermost layer composed of oxygen, aluminum, iron, and magnesium. Continental crust is thick and oceanic crust makes up most of the ocean floor. Mantle: Below the crust, mostly solid, and comprised of peridotite (silica, iron and magnesium) Core: Iron/nickel, liquid outer core, solid inner core, Rotations generate Earth’s magnetic field. Rock Categories: -Igneous -Metamorphic -Sedimentary 1.Magma is formed in Earth’s surface 2. Magma cools solidifying during crystallization (forming igneous rock) 3. Igneous rocks face weathering, erosion which produces sediments 4. Sediments are broken down and transported through rivers, glaciers and wind 5. Sediments begin to layer on top of each other and fused by groundwater 6. The compaction and cementation are called lithification (sedimentary rock) 7. Metamorphic rock can be formed from pre-existing rock by changes such as high temps/pressure Isostasy: The relative position of Earth’s crust. The “thicker” the layer, the deeper it is Objective observation: factual statement Subjective observation : An opinion Qualitive: Descriptive data that does not involve numbers Quantitative: Numerical data Precambrian Eon: Oldest and longest eon 88% of Earth history Phanerozoic era- 541 million years ago Paleozoic era- 252-66 million years ago Cenozoic era- 66 million years ago to present Relative dating – relies on principles such as superposition (old on bottom, young on top) and cross cutting (features cutting through rocks are younger) Absolute dating- Assigns numerical value using radiometric dating techniques Superposition : (old on bottom, young on top) Original horizontality: Sedimentary layers are initially deposited horizontally. Tilted layers indicated later deformation Lateral continuity: Sedimentary layers extend laterally until they, thin out or terminate against a barrier Cross cutting relationships: A geological feature that cuts another is the younger of the two features. Faults/intrusions/erosion surfaces Inclusions : Fragments (inclusions) within a rock layer are older than the layer itself Fossil succession: Fossil organisms succeed one another in a definite and determinable anytime period can be recognized by its fossil content Radioactive isotopes are unstable atoms that decay at predictable rates 1 half life 50% 2 half life 25% 3 Half lives 12.5% Radiocarbon Dating: -14 (14C) half life is 5,730 year U-pb and A-kr dating are applied to igneous rocks: Body fossils are bodily remains of an organism (bones, shells, and fossils) direct evidence Trace evidence (footprints, burrows) indirect evidence Actual preservation: Original material is preserved (e.g., insects in amber). Several processes can preserve fossils: Permineralization: Minerals fill pores and spaces in organic material (e.g., petrified wood). Molds and casts: Original material dissolves, leaving a cavity (mold) that may be filled with sediment (cast). Carbonization: Organic matter is compressed, leaving a carbon film. Replacement: Original material is replaced by another mineral (e.g., bone replaced by silica). Rapid burial: Protects the organism from decay and scavenging. Hard parts: Bones, shells, and teeth are more resistant to decay than soft tissues. Anoxic environment: Lack of oxygen inhibits bacterial decay. Lithostratigraphic correlation: Matching rock units based on lithology (rock type and characteristics). Chronostratigraphic correlation: Matching rock units based on age, even if lithologies differ. Biostratigraphic correlation: Matching rock units based on fossil content (index fossils). Nonconformity: Sedimentary rocks overlying igneous or metamorphic rocks. Disconformity: Parallel sedimentary layers separated by an erosional surface. Angular unconformity: Tilted or folded sedimentary rocks overlain by younger, horizontal layers. 1. Zircons: Ancient zircon crystals (4.4 billion years old) indicate the existence of continental crust at that time. 2. Greenstone belts: These ancient rock formations contain evidence of early volcanic activity and sedimentary processes. 1. Radiometric dating of meteorites: Meteorites provide samples of early solar system material. 2. Radiometric dating of lunar samples: Lunar rocks provide independent age estimates. 3. Radiometric dating of Earth's oldest rocks: The oldest known rocks on Earth provide a minimum age. Great Oxidation Event (GOE) The GOE, around 2.4 billion years ago, marks the significant increase in atmospheric oxygen. Evidence includes: 1. Banded iron formations (BIFs): These sedimentary rocks contain alternating layers of iron oxides and chert, indicating fluctuating oxygen levels. 2. Red beds: Sedimentary rocks containing iron oxides (hematite), which require oxygen for formation. Role of Cyanobacteria Cyanobacteria (blue-green algae) played a crucial role in the GOE through photosynthesis, releasing oxygen as a byproduct. A second oxygenation event occurred later in the Proterozoic. Phanerozoic Eon: Eras and Organisms The Phanerozoic Eon is divided into three eras: Paleozoic, Mesozoic, and Cenozoic. Each era is characterized by specific organisms: Precambrian: Early life forms, including stromatolites (bacterial colonies) and single- celled organisms. Paleozoic: Marine invertebrates, plants, amphibians, reptiles. Mesozoic: Dinosaurs, angiosperms (flowering plants). Cenozoic: Mammals, birds, primates, humans. Major Extinction Events Precambrian-Paleozoic boundary: The end-Ediacaran extinction. Permian-Triassic boundary ("Great Dying"): Earth's largest mass extinction, caused by massive volcanism in Siberia. Cretaceous-Paleogene boundary (K-T extinction): Extinction of the dinosaurs, likely caused by an asteroid impact. Last Ice Age Megafauna Extinction: Likely caused by climate change and human hunting. Antarctic Circumpolar Current The development of the Antarctic Circumpolar Current in the Cenozoic significantly impacted global climate by isolating Antarctica and leading to its glaciation. Plate Tectonics Plate Tectonics Theory Plate tectonics is the theory that Earth's lithosphere is divided into several large plates that move relative to each other. This movement causes earthquakes, volcanoes, mountain building, and the formation of ocean basins. Continental Drift Hypothesis Alfred Wegener proposed the continental drift hypothesis, suggesting that continents were once joined together in a supercontinent (Pangaea) and have since drifted apart. Evidence included:  Matching coastlines. Similar fossils and rock types on different continents. Evidence of past glaciation in now-tropical regions. The hypothesis was initially rejected due to a lack of a plausible mechanism to explain continental movement. Seafloor Spreading and Magnetic Stripes Seafloor spreading is the process by which new oceanic crust is created at mid-ocean ridges and spreads laterally. The magnetic stripes on the seafloor are formed by the periodic reversals of Earth's magnetic field. The outer core's movement generates Earth's magnetic field. The discovery of these magnetic stripes provided strong evidence for seafloor spreading and plate tectonics. Evidence for Seafloor Spreading Three lines of evidence support seafloor spreading: 1. Magnetic stripes: Symmetrical patterns of magnetic anomalies on either side of mid- ocean ridges. 2. Age of ocean crust: Ocean crust is youngest at mid-ocean ridges and gets progressively older away from them. 3. Sediment thickness: Sediment layers are thinner near mid-ocean ridges and thicker farther away. Plate Boundaries Three types of plate boundaries exist: Boundary Type Plate Motion Characteristics Magma Formation Divergent Plates move apart Mid-ocean ridges, rift valleys, volcanic activity Decompression melting Convergent Plates collide Ocean trenches, volcanic arcs, mountain ranges, subduction zones, accretionary prisms Flux melting (volatiles lower melting point of mantle) Transform Plates slide past Transform faults, earthquakes Generally no magma formation Subduction Subduction is the process by which one tectonic plate slides beneath another. This occurs at convergent boundaries where denser oceanic plates subduct beneath less dense continental or oceanic plates. Wilson Cycle The Wilson Cycle describes the cyclical opening and closing of ocean basins. It begins with continental rifting, followed by seafloor spreading, subduction, and eventually the collision of continents. Mechanisms of Plate Tectonics Three main mechanisms drive plate tectonics: 1. Slab pull: The weight of a subducting plate pulls the rest of the plate along. 2. Ridge push: The elevated mid-ocean ridge pushes the plates apart. 3. Mantle convection: Convection currents in the mantle transfer heat and drive plate movement. Plate Movement Tectonic plates move at an average rate of a few centimeters per year. Direct evidence for plate movement includes: 1. GPS measurements: Precisely track plate motion. 2. Earthquake epicenters: Locate plate boundaries and movement. 3. Hotspot tracks: Chains of volcanoes formed as a plate moves over a stationary hotspot. Hotspots Hotspots are volcanic regions thought to be fed by mantle plumes—columns of hot, upwelling mantle material. They are not associated with plate boundaries and provide evidence for plate movement by creating chains of volcanoes as the plate moves over the stationary hotspot. Volcanic Island Arcs vs. Chains Volcanic island arcs are curved chains of volcanoes formed at convergent boundaries. Volcanic island chains are linear chains of volcanoes formed by hotspots.