Geology Exam 1 Study GuideChapter 1- Scientific Method: a sequence of steps for systematically analyzing scientific problems in a way that leads to verifiable resultso Observation: collecting observations on clues that point to an answero Hypothesis: possible explanation that can explain a set of observationso Theory: scientific ideas supported by an abundance of evidence- Principle of Uniformitarianism: The processes we see today like erosion, volcanism, etc. were also present in the past.- Nebular Hypothesiso NEBULA: area of space dominated by “dust”o Starts to collapse under its own gravity, stars form the centero Collapse causes the nebula to spin fastero As it spins faster, it flattens out into a disko The dust starts to clump up into larger pieces “Planetismals”- How was the moon formed? Why is the Earth’s orbital plane tilted?o Sometime during the late stages of accretion a Mars-sized body impacted the Earth, resulting in1. Ejecta of debris into space2. Speed up the Earth’s rotation3. Tilting of Earth’s orbital plane to 23 degrees4. Forming our moon- How old is Earth?o 4.53 billion years old- How did Earth’s continents, atmosphere, and oceans form?o Continents-formed from the lighter molten materials rising to the surface due to differentation and solified as it coolso Oceans/Atmosphere-2 hypotheses Resulted from impact of volatile-rich matter impacting Earth from space early after it was formed such as comets Resulted from volatile tied up in planetismals which formed the Earth Combination of both- Theory of Plate Tectonics/Driving forceo Outer portion of Earth (lithosphere), is not continuous. About 12 larger plates.o Plates move! Act as rigid units that ride on the athenosphere which is also in motion—few cm per year(approx. 5.5 cm/yr)o Most geologic activity is near plate boundarieso Plate interiors are relatively quietChapter 2- Continental Drift Hypothesis (evidence supports Wegner’s hypothesis)o Continental fito Patterns of present day animal lifeo Fossil evidenceo Related rockso Ancient climates1. Wegner lacked a mechanism. He had no way to move the continents.2. Incorrectly believed that only continents were moving.3. Continents are not independent plates. Often made of both continental& oceanic lithosphere- Divergent Boundaries- Plates more away from one another (ocean basins)o Sea floor spreading- new oceanic lithosphere is created where partially molten mantle material rises to fill the gap of the rift.o Rift- a crack like valley which allows molten rock to erupt from belowo Ex. Mid Atlantic Ridge/Iceland/Sea of Cortezo Decompression Melting- as hot mantle material rises the drop in pressure results in melting of the rock- Convergent Plate Boundaries- Plates move toward each other (earthquakes &volcanoes)…Collisions or subduction (one plate sinks under the other, denserone) occurs3 Types of Convergent Plate Boundaries:- Continental-Oceanic Convergence (The Cascades, The Andes):o Deep sea trencho Subduction zoneo Chain of volcanoes along subduction zoneo Accreationary prismo Earthquakes - Oceanic-Oceanic Convergence (Japan, Philippines)o Deep sea trencho Subduction zoneo Chain of volcanoes=Island Arc (igneous rocks)o Earthquakes- Continent-Continent Convergence (Himalayas)o Two continental plates collide (compression)o No subductiono Earthquakeso Rocks of any type may convert into metamorphic rocks from increased temperatures & pressure- Transform Boundarieso Plates shift past one another laterally (generates earthquakes)o Volcanoes presento Commonly offset divergent boundary in the ocean but also form on continentso Ex. San Andreas Faulto Fault: fracture in the crust along which there has been movement- Hot Spots (Hawaii, Yellowstone)o Stationary, surface expression of volcanic activityo Result of thermal plume, a localized source of rising heat energy from the mantle core- How did the crust on the Earth form?o Divergent Boundaries- Decompression Melting-forms oceanic lithosphereo Convergent Boundaries (w. subduction zone)- Both create/destroy- Flux melting-water- New land through volcanoismCHAPTER 3- What is a mineral?o Naturally occurringo Inorganic-no organic carbono Crystalline solid-atoms in a particular structureo Specific chemical compound-particular elements in set ratio- What is an isotope?o Isotopes- # of neutrons may change- Chemical Bonding: atoms combine by losing or gaining or sharing electrons to form mineralso Ionic Bonding (Weak): Transfer of electrons Form when shells are nearly empty or full WEAK BONDo Covalent Bonding (Strong): Sharing of electrons Form when shells are about half full STRONG BOND- What mineral will form?o Available elementso Ionic substitutiono Conditions of crystallization Polymorphs- same composition but diff. crystal structure (Diamond/Graphite)- How do minerals form?o Chemical reactions between elementso Crystallization- the growth of a solid from a gas or liquid whose constituents come together in the proper chemical proportions and crystalline arrangement- Where do minerals come from?o Lower the temperature of a liquid below its freezing point (ex. snow)o Evaporites- liquids evaporate from a solution causing minerals to precipitate. Salt deposits found worldwide.o Hydrothermal- fluids created by the circulation of water through hot rock or near a magma chamber.o Metamorphism-high heat and pressure allows different minerals to formwhile still in the solid state (nothing melts) Garnets and other metamorphic minerals form by diffusion- slow movement of atoms due to thermal energy (heat)- Mineral Properties:o Color Least reliable-do not use alone Color depends on certain ions (iron, chromium, cobalt)o Luster How the surface reflects light Metallic vs. non-metallico Streak Color of mineral in powder state (scratching against white slate)o Cleavage The tendency of minerals to break along the planes of weakness Weaknesses within the structure allows the mineral to breako Fracture Breaks randomlyo Hardness A mineral’s resistance to scratching Moh’s Hardness scaleo Specific Gravity (SG) Ratio of weight to an equal volume of water How heavy it feels to another- Silicates- most abundant mineral group/dominate all three rock types- What makes a GEM? 5 factorso Beauty- as reflected by color or lustero Transparencyo Brilliance- enhanced by cutting or polishingo Durability- based on hardnesso Rarity- Diamonds-Brought up SLOWLY=Graphiteo