Geology Notes: Earth Science and Principles - PDF

CH. 1: Understanding Science ​ Geology is the science of the earth ​ Geology studies Earth’s compositions, structure, origin, life forms, physical and chemical processes affecting it, and its history. ​ Geology is interdisciplinary. ○​ It involves the understanding of physics, che...

CH. 1: Understanding Science ​ Geology is the science of the earth ​ Geology studies Earth’s compositions, structure, origin, life forms, physical and chemical processes affecting it, and its history. ​ Geology is interdisciplinary. ○​ It involves the understanding of physics, chemistry, biology, mathematics, astronomy, and other sciences. ​ Geology=unique? ○​ Geology involves time ○​ 4.5 billion years of history ​ Study Geology to: ○​ Locate, extract, and manage natural resources ○​ Evaluate the environmental impacts of using or extracting these resources ​ Geology controls the distribution of resources: ○​ Age and type of rocks, regional geologic history ​ Mineral resources ○​ Iron (banded iron formations) ○​ Copper ○​ Salt ​ Study geology to: ○​ Estimate/mitigate: hazards and risks ○​ Estimate: likelihood of future events ○​ Understand: what happened in the past ​ Geology influences our lives ○​ Natural hazards: ​ Hurricanes, flooding, earthquakes, volcanoes, landslides ○​ Geologic hazards occur in specific locations for specific reasons ​ Geology helps to explain Earth’s features ○​ Like the landscape features of North America ​ Mountain ranges ​ Valleys  ​ Volcano distribution ​ Continental positions ​ Geology provides evidence of ancient life ​ Geology provides evidence of past global climate change ​ What does a geologist do? ○​ Geologist: scientist who studies the Earth’s structure, composition, and history ○​ They play a crucial role in understanding the planet we live on and its resources ○​ EX: ​ Fieldwork and mapping ​ Lab work ​ Computer work ​ Report writing ​ Geologists study ○​ Natural hazards to understand the risks to communities Earth’s resources (rocks & minerals, oil, gas) for economic developments ○​ Rocks, fossils, and structures to understand processes that have and continue to shape the planet ​ Many diff types of geologists ○​ Geochemist ○​ Volcanologist ○​ Env. geologist ○​ Geobiologist ○​ Etc. ​ Modern science is based on the scientific method ○​ Def: : involves systematic observations, measurements, and experiments, and the formulation, testing, and modification of hypotheses. ○​ 1. Make an observation, identify a problem, and/or form a question  ○​ 2. Form one of more hypotheses (explanations) ​ Def: an explanation for an observation that can be tested ○​ 3. Conduct an experiment, hypothesis revision ○​ 4. Peer review, publication and replication ○​ 5. Scientific theory development ​ a hypothesis that has been repeatedly tested for falsifiability through documented and independent studies ○​ The scientific method ​ The scientific method is a continuous, ongoing process. ​ Science is self-correcting process ​ Observations vs interpretations ○​ Observation: a comment/statement about what you see/perceive. ○​ Interpretations: a logical scientific inference based on the observations and numerical data and any prior knowledge, to form a conclusion. ​ Scientists strive to be as unbiased as possible ○​ Objective observation: no personal biases; same for all individuals, based on verifiable facts ○​ Science uses experimentation to objectively reach conclusions. ○​ Subjective observations: biased because it involves a person’s feelings, beliefs; not same for all individuals ​ Quantitative vs Qualitative ○​ Qualitative: descriptions, observation based on non-numerical data (words, sketches, images) ○​ Quantitative: observations based on numerical data using tools, instruments, machines. (measurements collected in the field or samples analyzed in a lab) ​ Geology is based on observations and facts about nature ​ Principle of Uniformitarianism: ○​ Processes at work today are the same as how they worked in the past: “the present is the key to the past”. ​ Investigating geologic questions ○​ Observations + measurements questions >> & interpretations ​ Observed rocks at the rim of the crater: ○​ Are angular blocks of fractured shattered limestone and sandstone ○​ Presence of tiny minerals that form under very high pressures ○​ Presence of meteorites around the crater ​ Observed rock layers at the site: ○​ The same type of rock found beneath the region ○​ The crater is within sedimentary layers. ​ Evidence indicates: ○​ Meteor impact ​ Foundation of modern geology: ○​ Began to develop in the 17th and 18th centuries ○​ Nicolaus Steno (1638-1686): studied geology and anatomy ​ Proposed the law of superposition: in undisturbed layers of rock, the oldest layers are at the bottom and youngest at the top ​ Nicolaus Steno's (1667) classic demonstration that fossils represent the remains of ancient animals.  ○​ James Hutton (1726–1797) ​ The “Father of Modern Geology” ​ Theory of the Earth, 1795 ​ rock cycle ○​ Sir Charles Lyell (1797-1875)​ ​ 1830s published: ​ Principles of Geology ​ Elements of Geology ​ Promoted and led to the acceptance of ___ by the scientific community and public ○​ _____ (1880-1930) ​ Proposed hypothesis ____ ​ Theory of ____ ​ Earth in our solar system ○​ Earth is in the ____ ○​ (distance from Sun= temperature just right for H2O to be liquid; ideal for life) ​ How did Earth’s layers form? ○​ By _____: materials separate based on ____ ○​ Primitive planets start off homogeneous (have a uniform distribution of material) ○​ Shortly after a planet forms it will differentiate into layers ​ Dense material sinks to the center, light material floats to the top. ​ Earth’s layers ○​ Chemical layers: defined by average composition ​ ________ ○​ Physical layers: defined by physical properties ​ ________ ​ Earth’s compositional Layers ○​ Crust: ​ ____:  ​ Average composition is ____ ​ Avg. thickness is ______ ​ OC lines the _____________ ○​ _____: ​ Avg. composition is ____ ​ Avg. thickness is ___ ​ CC is our _________ ​ CC is _______ more than OC ○​ _______ : ​ Directly below crust, extends to ______________ ​ Most _______ of layers ​ Average composition is ______________ ​ Mostly solid rock (but _______ _________), some molten due to high temps. ○​ ​ _______ : ​ Directly below the mantle. ​ _______ layer. ​ Mostly ________________ with other trace elements. ​ Earth’s magnetic field ○​ Convection/movement of ______________ produces electrically conducting fluid generating Earth’s magnetic field called the _________________________. ​ Earth’s physical layers ○​ Lithosphere: crusts + upper mantle ​ Outermost layer ​ Strong, rigid, brittle, broken into plates ○​ Asthenosphere: base of lithosphere to 410-660 km ​ Weak, solid but flows (ductile) ○​ Mesosphere: base of asthenosphere to the core boundary ​ More rigid and immobile than the asthenosphere  ○​ Outer core: liquid ○​ Inner core: solid ​ Plate tectonics ○​ The theory that the outer layer of the earth (the lithosphere) is broken in several plates that move relative to one another ​ Why are some regions higher in elevation than others? ○​ Observe: difference of height and thickness of each block relative to other blocks: ​ Thick block is higher than ​ Dense materials (like a ​ the thin block ​ ​ ​ a denser wood) are lower ​ Isostasy: relationship between crustal thickness, density, and elevation ○​ Oceanic crust is denser than continental crust ​ The rock cycle: ○​ The process in which a rock can be moved from one place to another or converted into a different type of rock. ○​ Three major rock categories, base on how the rock is formed: ​ Sedimentary rocks: ​ formed from the weathering/breakdown of preexisting rocks ​ Accumulation of sediments (rock fragments) on earth’s surface ​ Igneous rocks: ​ Formed from the crystallization and solidification of magma and lava ​ Volcanic ignition rocks form on earth’s surface ​ Metamorphic rocks:  ​ Formed from alteration of preexisting rocks due to increase in temperature and pressure ​ Earth’s system: ○​ The sum of the physical, chemical, and biological processes operating on and within the Earth. ○​ Geosphere: solid Earth (rocks and soil) ○​ Atmosphere: gaseous envelope surrounding the Earth ○​ Biosphere: all living organisms ○​ Hydrosphere: all water on Earth ○​ Cryosphere: all frozen water ○​ The earth’s spheres are a combo of systems that interact and influence one another via complex relationships ○​ The Earth’s spheres interact and influence one another via: ​ Cycling of Elements ​ Oxygen ​ Hydrogen ​ Carbon (chapter 15 lecture) ​ Nitrogen ​ Phosphorous ○​ Cycling of elements by: ​ Biogeochemical processes: biotic; involves organisms ​ Geochemical processes: abiotic ​ Reservoirs and transport pathways of Earth’s System ○​ Reservoirs are places where elements are stored in the Earth system. ​ Rocks, oceans, atmosphere, plants, animals, etc. ○​ Transport pathways are the mechanisms/processes that move elements between the reservoirs. ​ Processes: evaporation, precipitation, chemical weathering of rocks, volcanic outgassing, photosynthesis, etc.  ​ Hydraulic cycle ○​ The movement of H2O (liquid, solid, gas) through Earth’s 5 spheres. ○​ precipitation= amt/type of vegetation ○​ volcanoes= gasses into atmosphere CH. 7 Geologic Time Scale and Earth History: ​ Geologic Time Scale ○​ Reflect major episodes in Earth’s development ​ Continental positions (plate tectonics ​ Life ​ Climate ○​ First built using ​ Fossils ​ Relative dating methods ​ Then numeric ages applied ​ Concept of Geologic Time: ○​ Geologists are Earth’s historians strive to establish order of events throughout Earth’s 4.6 billion years ○​ William Smith, 1790s ​ Observed similar rocks in different areas ​ Observed consistent sequences of rock layers that recorded the progression of time ​ 1 st geologic map of Britain ​ Noted different fossils in different rock layers ​ The layers contained a predictable succession of fossils ​ The Geologic Time Scale ​ ○​ A 4.6 Ga calendar if Earth’s history ​ System for organizing Earth’s history into units of time ​ Eons >> Eras >> Periods >> Epochs >> Ages ​ Division of the Geologic Time Scale ○​ Eons: Precambrian Eon:(4.6 Ga-541 Ma) ​ 88% earth’s history ​ Very early Earth: ​ hellish/alien environment ​ molten ball of rock (magma ocean) ​ first crust by 4 Ga: ○​ greenstones → ○​ shattered rocks from impacts ○​ lots of meteorite impacts ​ First atmosphere (toxic/anoxic) ○​ Mantle a lot hoƩer = Lots of volcanism ○​ Outgassing = volcanic gasses formed early atmosphere ​ First atmosphere was toxic & anoxic atmosphere ​ H2 , CH4 , NH3 , H2O, CO2 , N2 , SO2 ​ lighter gasses escaped Earth’s atmosphere, while heavier gasses prevented from escaping into space by gravity ​ Precipitation: source of water and salts (dissolved minerals from weathering of crust) in early oceans ​ Major Oxygenation Events: Free oxygen spiked ~ 2.4-2.3 Ga = the Great Oxygenation Event ​ 2nd oxygenation event, larger than first, ~ 0.7-0.6 Ga ​ Evidence of 1st indications of free oxygen: ​ Banded Iron Formations (BIFs) ○​ Increase in oxygen caused dissolved iron to deposit on ocean floor ○​ Mostly found in rocks between 3.6-1.9 Ga ​ Continental red beds; oxidation ○​ Well-oxidized, iron-bearing sediments ○​ Appearance in the rock record after 2.3-2 Ga  ​ Earth’s first life began in the oceans oldest fossils 3.5-3.6 Ga - simple, tiny cells or strands of cells of cyanobacteria ​ ^fossil evidence from Australia ​ Algae added oxygen via photosynthesis ​ Cambrian Explosion(~542-541) ​ The boundary between the end of the Precambrian Eon and start of Phanerozoic Eon = Cambrian explosion ​ Refers to the sudden appearance of numerous and diverse complex marine animals with mineralized skeletal remains (hard parts) in the fossil record ○​ Phanerozoic (meaning “visible life”): ​ 12% earth’s history ○​ Three Eras of the Phanerozoic ​ Paleozoic era (541 Ma- 252 Ma) ​ Paleozoic is known for the 1st fish, amphibians, insects, reptiles, land, plants to evolve, break up of Rodinia supercontinent and then beginning of Pangaea supercontinent. ​ Early Paleozoic: corals, crinoids, mollusks, trilobites, snails, shelled creatures with tentacles ​ Middle Paleozoic: fish became diverse, large reefs of coral 1st on land: plants included ferns and seedless trees, then insects appeared ​ Late Paleozoic: ○​ First vertebrate animals on land ○​ amphibians and early reptiles ○​ Gymnosperm plants(flowerless plants) became widespread on land ○​ Insects diversify Marine life continues to diversify  ​ End of the Paleozoic: ○​ The Great Dying (252 Ma) ○​ ‘Permian-Triassic Extinction Event’ ○​ Deadliest mass extinction event in Earth’s history ○​ Estimated 96% of all life perished ​ long recovery time: 4-6 million years before diversity increased ​ up to 30 million years for full recovery of terrestrial vertebrates ○​ Cause and duration of the extinction event remain uncertain. ​ Volcanic activity in Siberia and China = Siberian Traps ​ Put massive amount of CO2 in the atmosphere (greenhouse gas) ​ sea level dropped ​ reduced the area of shallow seas ​ Aridity on continents increased ​ Meteorite impact (3He extraterrestrial) ​ Deep sea anoxia ​ Mesozoic era (252 Ma – 66 Ma) ​ Known most for Reptiles (dinos), and Angiosperms(first flowering plants) ​ Along with Dinosaurs, first birds and mammals appeared ​ Pangaea supercontinent forms and starts to break apart ​ Early Mesozoic (Triassic): small dinosaur-like creatures, early mammals, seed-bearing conifers  ​ Middle Mesozoic (Jurassic): dinosaurs diversified, seas flourished with ammonites, star fish, large marine reptiles ​ Middle Mesozoic (Jurassic): dinosaurs diversified, seas flourished with ammonites, star fish, large marine reptiles ​ Late Mesozoic (Cretaceous): flying reptiles, larger dinos, flowering plants (angiosperms) ​ End of the mesozoic ○​ KT Extinction ○​ Non-avian dinosaur became extinct ​ Terrestrial and marine ○​ Late Cretaceous dino population declining ○​ Deccan Traps: extensive volcanic activity ○​ Change in continental configuration and ocean circulation ○​ Global temperatures falling ○​ Sea level drop ○​ Impact of the Chicxulub meteorite ​ Shocked quartz ​ Concentrated iridium layer ​ Crater site of impact ​ Cenozoic era (66 Ma- present) ​ Known for major diversification of Mammals ​ All non-avian dinosaurs extinct and left a large niche open ​ Mammals diversified and dominate the animal kingdom ○​ Mammals take to the oceans: dolphins and whales ​ Diversification of plants, insects, and other animals  ​ Terrestrial life ○​ Appearance of carnivorous mammals (early wolves, cats, bears…) ○​ Early primates (small, arboreal) were around ​ Lemurs ​ Monkey and ape-like primates African & Eurasian forests ​ Terrestrial plants ○​ Great diversification angiosperms(flowering plants) ○​ Grasses appeared appeared as global climate cooled and became more arid ○​ Evolved to have continuous growth ○​ Could recover quickly after being grazed upon ​ Late Cenozoic Ice Ages (antarctic glaciation) ○​ Antarctic circumpolar current established ​ Late Cenozoic: ○​ Modern taxa: familiar creatures ○​ Late Ceno, Ice Ages (Antarctic Glaciation) ​ Large bodied animals ○​ Appearance of humans! ​ 1 st hominin ~7-6 Ma; bipedalism ​ Homo sapiens (us) ~300,000 yrs ago ​ Late Mesozoic-Cenozoic paleoclimate record  ○​ -zoic = life, Ceno- = newMeso- = middle , Paleo- = ancient ○​ Jurassic Park ​ Tyrannosaurus Rex ​ Lived in Cretaceous period ​ Feathered, slower (10-25 mph), better sight ​ Biggest: Up to 30 ft long, 3,000lbs ​ Velociraptors ​ Smaller (turkey sized) ~30lbs and feathered ​ Weren't particularly big, smart, or speedy ○​ Fossils and film ​ Mary Anning (1799 – 1847) was a British fossil collector and paleontologist, major contributor to Jurassic marine fossils and modern paleontology ​ Plesiosaurus: large extinct marine reptile ​ Ice Age Megafauna (125,000-14,500 years ago) ○​ End of the last Ice Age (10,000 yrs ago) ​ Extinction of the megafauna, 11,000 years ago ​ Cause of extinction ​ Overkill hypothesis or climate change hypothesis ​ Development the Geologic Timescale ○​ Geologic Time Scale first built based on: ​ Relative dating principles: determining a sequence of events (oldest to youngest) based on relative positions/relationships of features ​ Use of geologic principles (relative dating principles) along with Law of Uniformitarianism ​ Used to reconstruct the geologic history and order of events ​ Investigating the geologic history of an area ○​ Stratigraphy: study of rock layers and their relationships  ○​ Geologists use relative dating principles (principles of stratigraphy) and the Law of Uniformitarianism to help reconstruct geologic history. ○​ Accompanied by use of absolute dating methods to know when events occurred in Earth’s history! ​ Development the Geologic Timescale ○​ In late 1800’s discovery of radioactivity ​ radioisotopes decay at a constant rate ○​ Absolute dating method: a way to calculate timing of events and rates of geologic processes ​ assigning a numeric age to an event, rocks or other geologic material. ​ Quantitative method ​ Methods include: Radioisotope dating, cyclical features (tree rings, varves, layers of ice forming thick ice sheets) ​ Relative vs. absolute (numeric) methods ○​ Relative: Which unit is older than the other? ○​ Absolute: How long ago did the event occur? ​ Why do we investigate geologic history as an area? ○​ To understand Earth history ○​ Understand the geologic processes that have occurred in the past and that are occurring today ○​ Helps in exploration for natural resources ​ Like determining whether oil is trapped at depth or would have escaped to the surface ○​ Helps to evaluate geologic hazards ​ Volcanic eruptions: last erupted, eruption history ​ Flooding: recurrence of flood events ​ Earthquakes: rupture history, recurrence rate ○​ Six key relative dating principles:  1.​ Principle of superposition: states that in an undisturbed succession of strata, the oldest layers are at the bottom, and successively younger layers are above. 2.​ Principle of original horizontality: states that sedimentary layers were deposited nearly horizontally and parallel to the Earth’s surface. 3.​ Principle of lateral continuity: strata layers are continuous in all directions until they thin out at the edge of that basin 4.​ Principle of cross-cutting relationships: a rock unit, sediment body, or fault that cuts another geologic unit is younger than the unit that was cut. [youngest feature cuts older features] 5.​ Principle of inclusions (included fragments): fragments of rock within a larger rock unit are older than the rock it’s enclosed within. 6.​ Principle of fossil succession: systematic change of unique fossils through time due to evolution. a.​ Fossils occur in definite, determinable order because evolution is linear. b.​ Observations of fossils changing upward from older to younger rocks, helped to build the geologic timescale. ​ Unconformities ○​ Unconformity: a surface between rock layers of greatly differing ages, which represents ‘missing time’ in the rock record. ○​ Two causes that form unconformities: ​ A period of time when there was no deposition ​ Rocks were removed (erased) by erosion) ○​ Unconformities form as a result of sea level change, surface uplift and subsidence, or tectonic forces. ○​ Types of unconformities: ​ Angular unconformity  ​ Erosional surface with flat/horizontal rock layers above and tilted rock layers below ​ Horizontal sedimentary rock layers ​ folded/tilted rock layers ​ Nonconformity ​ Erosional surface between sedimentary rocks and crystalline rocks ​ Horizontal sedimentary rock layers ​ Igneous or metamorphic rock (Non-layered) ​ Disconformity ​ Visible, uneven or irregular erosional surface between parallel sedimentary rock layers of different age ​ Horizontal sedimentary rock layers ​ Younger horizontal sedimentary rock layers ​ Absolute Dating ○​ Absolute dating: assigning _______________ ○​ Used to know how long ago a rock formed or when a geologic event occurred ○​ Used to calculate the rate of geological processes ​ seafloor spreading, mountain building, erosional events. ○​ _______________ : the science of determining the age of rocks, sediments, fossils through various absolute dating methods. ○​ Geologists whose research work focuses on geochronology are called: Geochronologists ○​ Most common absolute dating technique: __________________ ○​ Radioactive isotopes (radioisotopes) are unstable isotopes. The atoms of some elements have different forms when they have ______________________________________________. ​ Stable isotopes and unstable (radioactive) isotopes ​ Radioactive Decay ○​ Radioactive isotopes break down, spontaneously decay, over time in a process called ____________________. ​ Radioactive isotopes decay to more stable isotopes ○​ Exponential decay of radioisotopes (parent atoms) to stable isotopes (child-daughter atoms) ​ Decay rate; half-life radioactive isotopes ○​ Each original unstable isotope, called the __________, gradually decays to form a new isotope, called the ____________ ○​ Before decay, all unstable parent atoms ○​ After __________, __ the parent (green) atoms decayed to child (purple) atoms (time = half life) ○​ After a _____ _____________of the parent atoms remain ​ Radiocarbon Dating ○​ decay of ____________ ____________ ○​ Organic materials in sediment, like _______________________________ ○​ ___________: used on material no older than 60,000 years old because of half life rate if relatively fast ​ Common radioactive decay series ○​ Isotopes are important: each radioisotope decays at a ________________ __________, unique to that radioisotope. ○​ To determine when a rock formed: ​ need to know ratio of ______________________in the sample ​ using the known __________________for the analyzed radioisotope to calculate how many years of decaying has occurred ​ Use of Multiple Radioactive Decay Series and on different minerals ○​ Several methods can be used on a rock to determine when it formed and how fast it cooled Lecture 10-Plate Tectonics: ​ 3 types of relative plate motions 1.​ Move apart: divergent boundary 2.​ Move toward each other: convergent boundary 3.​ Move horizontally past one another: transform boundary ​ Convergent boundaries: ○​ Where lithospheric plates move towards each other and the crust is deformed or destroyed (when subducted). ○​ Converging of plates causes: ​ Shortening and thickening of crust = mountain belt ​ Faults and rock deformation (folding, tilting of layers) ○​ Two types: ​ Both types have trench, accretionary wedge, and volcano 1.​ Subduction a.​ Oceanic-oceanic convergence i.​ Volcanic island arc b.​ Oceanic-continental convergence i.​ Continental volcanic arc 2.​ Continental collision ○​ Subduction zones: ​ Def: when the denser plate is pushed beneath the more buoyant plate and into the mantle ​ Subduction zones can produce the largest earthquakes and tsunamis ○​ Continental collision ​ Two continental lithospheric plates converging ​ No subduction = continental crust too buoyant ​ Region that’s experiencing crustal thickening, uplift of crust, mountain building ​ Characterized by ​ Tall, broad mountain w/high plateau on one side ​ No volcanism  ​ Earthquakes ​ How continental collision forms ​ Subduction closes oceans leads to joining of continents ​ Ex. supercontinents (Pangaea) When continental edges touch: ○​ Subduction stops, ending volcanism ○​ Suture zone and fold-and-thrust belt forms ​ Material from the accretionary prism, continental shelf, and ocean floor scraped up and squished becoming part of the mountain belt. ​ Divergent Boundaries ○​ Where lithospheric plates move away from each other ​ Caused by tensional forces and/or mantle upwelling ○​ Diverging plates have: ​ Crustal stretching/extension and thinning ​ Faults and rift valleys ​ Moderate shallow earthquakes occur ​ Volcanism common ○​ Two types 1.​ Continental rifts 2.​ Mid-ocean ridges ○​ Continental rift zones ​ Mantle rising = pressure lowering, results in magma ​ Narrow rifts ​ Broad rifts ​ Failed continental rifting ​ Large scale rifting produce multiple rift branches, Some branches die out >> failed rift arm