GSCI 1050 Final Exam
Determine whether or not a given igneous rock sample is intrusive/volcanic/mafic/felsic.
Intrusive (crystals) vs. Volcanic (pretty much solid color) Mafic (darker) vs. Felsic (lighter)
Explain how a foliation is formed in a metamorphic rock.
Result of metamorphism - due to the pressure.
Describe the process of lithification.
(1) Compaction: pore spaces lefts between grains become smaller (2) Cementation: minerals deposited from water flowing through rocks, binds grains together
Describe the three Milankovitch Cycles and how they change Earth's climate.
(1) Eccentricity (2) Tilt of axis (3) Precession (wobble of Earth) - changes timing of seasons throughout the year
Describe the 3 ways to melt a rock.
(1) Increase temperature (2) Decrease pressure (3) Add volatiles (example: water)
Explain the 3 primary ways in which minerals form.
(1) Precipitation from a solution (example: seawater evaporates) (2) Cooling of a melt (example: most rocks in Earth's crust; Earth formed as a fiery inferno, once it solidified it cooled and certain minerals formed) (3) Metamorphism (example: carbon -> diamond)
Determine how many plates are present in a plate tectonic diagram.
(four plate tectonics in this diagram)
Identify the depositional environment of common chemical and biochemical sedimentary rocks (rock salt, travertine, coal, chalk, limestone).
Rock salt: (ocean?) Travertine: water springs or walls of caves Coal: swamp Chalk: deep marine Limestone: shelf/platform, reef, deep marine
Explain how chemical sedimentary rocks are formed, and differentiate between the formation of rock salt and travertine.
Rocks formed by chemical reactions. Precipitate from a solution as a result of changing physical or chemical conditions. Precipitation of minerals from chemical-rich waters.
Describe Earth's structural layers, including how that are arranged and what they consist of (the general composition only - for example, core consists of iron).
(in order of inner to outer layers) (Earth has big core, thin crust; like an apple) - Core: both inner and outer core are made of iron; inner core is much denser than outer core - Mantle: largest layer; iron, silicate metal compounds, magnesium, silicon, oxygen; denser than crust; composed mainly of very hot, solid rocks that flow - Crust: thin layer; made mainly of oxygen, silicon, aluminum
Explain how the characteristics of an igneous rock (color and texture) provide information on its cooling history (volcanic vs. intrusive) and silica content.
*Volcanic are dark and smooth, intrusive have lighter color and more crystals developed* Lighter color = higher silica content Bubbles = volcanic
Explain what unconformity is and what it represents.
- An erosion surface representing a gap in time between the formation of two sections of rock
Identify and describe the three types of unconformities.
- Angular = change is geometry - Disconformity = gap in time - Nonconformity = non layered rock (igneous, metamorphic) (involves non sedimentary rocks)
Given a specific depositional environment, name the rock that would likely form if the sediment found there were lithified into rock.
- Beach sand: quartz - Mountain cliff: large and angular pieces - Swamp: coal
Discuss the features, processes, and relative plate motions associated with a divergent plate boundary.
- Boundary at which two plates move apart from each other - Marked by mid-ocean ridges - New ocean floor forms
Describe how a clastic sedimentary rock is formed.
- Breakdown of rock to form sediment - Transportation of sediment - Deposition of sediment - Lithification
Discuss at least four factors that influence global temperatures over various timescales.
- Changes in Earth's orbit around the sun - Changes in the locations of continents - Changes in volcanic activity - Changes in oceanic circulation
Explain the process of metamorphism in general terms.
- Changes in the mineral composition and texture that can occur in any solid rock. - Changes due to increasing temperature and/or pressure.
Differentiate data vs. an interpretation.
- Data = facts and statistics collected together for reference or analysis - Interpretation = explaining the meaning of something; interpretations are made when data is deduced
List major events in Earth history in the proper order (Ex. first evidence of life, oxygenation of atmosphere, complex life evolves, life on land evolves, dinosaurs evolve, large mammals evolve, etc.)
- First evidence of life = 3.5 billion years ago - Oxygenation of atmosphere = 3.5 billion years ago - Complex life evolves = Cambrian Explosion; 542-530 million years ago - Life on land evolves = 400 million years - Dinosaurs evolve = Mesozoic - Large mammals evolve = Cenozoic
Provide three explanations why sea-level rises and falls throughout Earth's history.
- Glaciers (bigger = fall in sea level; smaller = rise in sea level) - Spreading rate (slower seafloor spreading = colder ocean floor = drop in sea level) - Temperature (oceans cools = drop in sea level)
List and describe common earthquake hazards.
- Ground shaking - After shocks - Landslides - Elevation changes - Liquefaction (loosely packed grains of soil are held together by friction; pore spaces are filled with water; shaking destabilizes the soil by increasing the space between grains; soil flows like liquid) - Tsunami
Pinpoint on a map of plate boundaries where you are likely to find more and less explosive volcanoes.
- Hotspots = less explosive - Lower in the Earth at subduction zones = felsic and intermediate rocks (more explosive)
Compare and contrast igneous, metamorphic, and sedimentary rocks.
- Igneous and sedimentary rocks formed in the crust; metamorphic rocks formed in mantle - Rock melted= igneous - Rock metamorphososed = metamorphic rock - Rock sedimented together = sedimentary rock
Identify the range of temperatures in which lithification, metamorphism, and melting at likely to occur.
- Lithification: < 200 degrees C - Metamorphism: 200-1100 degrees C - Melting: 1100-2000 degrees C
Describe the type of magma that drives volcanism on Hawaii, and why magma forms here.
- Mafic magma - Hawaii is an island arc created by a hotspot
Describe multiple reasons why Earth is hospitable to life, but other planets are not.
- Magnetic field protects the Earth from harmful radiation. - Liquid water - Earth has an abundance of water. - Habitable zone - just close/far enough away from the Sun. - Gravity and a protective atmosphere. - Life-sustaining gases. - Strong magnetic field. - Biosphere - removes CO2 and adds O2.
List the most common gases found in Earth's atmosphere and their relative proportions.
- Nitrogen @ 78% - Oxygen @ 21% - Other @ 1% (many of which are greenhouse gases)
Distinguish between observations, hypotheses, and predictions in the context of a scientific investigation.
- Observations: facts, measures, information, data collected using the senses - Hypothesis: a testable explanation or interpretation that can be verified or falsified - Prediction: a statement of what will happen in a given situation or set of circumstances
Describe the principles of original horizontality, superposition, cross-cutting, and inclusions and use them to interpret the relative order of events on a rock sequence diagram.
- Original horizontality = sediments are deposited in layers - Superposition = older rocks are at the bottom, younger rocks are at the top - Cross-cutting = faults and igneous intrusions; something cutting across rock layers is younger than what it is cutting across - Inclusions: if one rock has inclusions of another in it, we know that the inclusions come from the older rock
Pinpoint on a cross-section (side view) of plate boundaries where you are likely to find the different types of igneous rocks, where/how magma is formed, and whether the magma is felsic/mafic/explosive/non-explosive.
- Partial melting of continental crust = felsic - Partial melting of mantle = mafic - Subduction zone = felsic and intermediate magma
Compare and contrast plate tectonics with the continental drift hypothesis. (Ex. What information led to the acceptance of plate tectonics?)
- Plate Tectonics = Earth's surface divided into "plates" based on tectonic activity - Plate tectonics provided the continental drift hypothesis with the means as to how the plates moved - After rejecting Wegner's theory, scientists noticed underwater mountain ranges. Heat was forming from the underwater mountain ranges. As this magma and lava was cooling, it was creating new ocean crust. The idea of seafloor spreading proved there could be moving continents. *Evidence for seafloor spreading = plate tectonics is born*
Explain the motion associated with a transform boundary and where they can be found on Earth.
- Plates slide sideways past each other; lithosphere is neither created nor destroyed - Examples: San Andreas Fault, Alpine Fault/Macquarie Fault Zone (New Zealand)
Briefly describe the differences between the Precambrian, Paleozoic, Mesozoic, and Cenozoic divisions of the geologic timescale with respect to the evolution of life/species.
- Precambrian = life begins @ 3.5 billion years; early bacteria; no life on land - Paleozoic = insects and early reptiles on land; age of fishes; first land plants; first common organisms with hard skeletons - Mesozoic = first grasses and flowering plants; first birds; early dinosaurs and age of reptiles - Cenozoic = large mammals abundant
List (roughly) the time intervals that the Precambrian, Paleozoic, Mesozoic, and Cenozoic divisions of the geologic timescale represent.
- Precambrian = time before 543 million years ago - Paleozoic = 534 million - 299 million years ago - Mesozoic = 251 - 146 million years ago - Cenozoic = 65.5 years ago - modern day
Describe the ways in which rocks respond to metamorphism (Ex. recrystallization, neocrystallization, foliation, etc.)
- Recrystallization: changes size and shapes of grains - Neocrystallization: creating new minerals with different chemical compounds or crystalline structures - Foliation: a fabric defined by parallel surfaces or layers that develop in a rock as a result of metamorphism
Explain the process of partial melting and how that can change the composition of a magma.
- Some minerals melt, others do not (Felsic minerals = lowest melting temps.; mafic minerals = highest melting temps.) (Mafic minerals will crystallize first when magma cools)
Describe how stream flow characteristics change as a river flows downstream.
- Streamflow gets higher with more precipitation
Explain how oxygen isotopes and their ratios are used to infer past climate, and be able to interpret a graph of changes in the ratio of oxygen isotopes over time.
16O = lighter, evaporates more easily 18O = heavier, remains in oceans During warmer periods the ratio stays the same. During colder periods, there is less 16O. (16O is trapped in glaciers)
Differentiate between active and passive margins, and locate examples of each.
> Active Margins = plate boundaries > Passive Margins = not plate boundaries
Identify and describe these four common clastic sedimentary rocks: conglomerate, breccia, sandstone, shale.
> Conglomerate: coarse-grained; rounded clasts > Breccia: coarse; angular fragments > Sandstone: consisting almost entirely of quartz; lighter brown/yellow color > Shale: very fine-grained sedimentary rock that breaks into thin sheets
Explain the difference between contact and regional metamorphism, and where each is likely to occur.
> Contact = occurs due to increasing temperature (near magma) (no foliation) > Regional = occurs due to increasing temperature and pressure along plate boundaries
Describe how the locations of Earth's features and hazards are related to plate tectonics.
> Features often found near/on plate tectonics: island chains, mid-ocean ridges, ocean trenches, mountain ranges, continents, shelves > Most of the major geologic processes occur along the boundaries between plates.
Identify the 3 major rock types and where they can be found on (or in) Earth.
> Igneous Rocks: found in Earth's crust; near volcanoes; oceanic crust, subduction zones, hotspots > Sedimentary Rocks: found in/on Earth's crust > Metamorphic Rocks: found in the brittle-ductile transition zone, convergent and divergent boundaries Layers of Rock Formation (upper to lower): Lithification (sedimentary) Metamorphism (metamorphic) Metamorphism or Melting (depends on silica content of rocks) Melting (magma forms)
Explain how melting occurs at divergent and convergent boundaries.
> Melting at divergent: seafloor spreading, space is created for the asthenosphere to come up to the surface; temp. decreases slightly but the pressure decreases a lot and allows the asthenosphere to melt; decompression melting > Melting at convergent: partial melting
Compare and contrast the three types of convergent plate boundaries. Describe the geologic processes that characterize the three major types of plate boundaries.
> Oceanic/Continental: oceanic crust is more dense than continental crust, therefore oceanic crust will always subduct below continental crust; forms mountain ranges and volcanoes on the edge of the continent (example: Andes in South America, Cascade Mountain Range) > Oceanic/Oceanic: forms oceanic trenches, the result of one plate going below, deep, into the Earth; island arcs form (example: Mount Fuji, Japan's Island Arcs) > Continental/Continental: used to have an ocean basin that was subducted, but at some point the ocean basin ran out, and the continent began to subduct instead; subduction eventually stops because there is no more dense oceanic crust; forms the thickest crust on Earth (example: formation of the Himalayan Mountains)
Explain the difference between shield volcanoes and composite (strato) volcanoes, and where to find examples of each (ex. convergent boundary, divergent boundary, hotspot).
> Shield: subaerial volcano with a broad, gentle dome; formed from low-viscotiy basaltic lava or from large pyroclastic sheets; example = volcanoes of Hawaii; largest volcanoes; main product is lava; low silica magma > Stratovolcanoes: large, cone-shaped subaerial volcano consisting of alternating layers of lava and tephra; example = Mt. Fuji; subduction zones; pyroclastic flows; pose greater hazard
Sketch and label the three major types of faults.
> Strike-slip: motion along strike line; left lateral, right lateral > Normal fault: hanging wall moves down (extension) > Reverse fault: hanging wall moves up (compression)
Distinguish between the crust, mantle, lithosphere, and asthenosphere.
> lithosphere = crust and upper-most solid mantle > asthenosphere = part of the mantle below the lithosphere
Describe how the greenhouse effect works, and list the major greenhouse gases in the atmosphere.
Absorbed radiation from the Sun is usually reflected back out, but the greenhouse gases emit absorbed radiation that warms the Earth and its atmosphere. Major greenhouse gases: water vapor, carbon dioxide, methane
Define the term "albedo" and explain how it influences Earth's climate with respect to feedback loops.
Albedo = the fraction of radiation that is reflected by a surface or body - High albedo at the poles because of reflective snow; makes climate cooler
Explain the difference between the brittle and ductile zones in Earth, and at roughly what depth the transition takes place.
Brittle zone = low temperature, low pressure Ductile zone = high temperature, high pressure Transition is between 15-20 km.
Explain multiple reasons why locations with similar latitudes can have vastly difference climates.
Climate is not just dependent on latitude - also depends on amount of precipitation, altitude, proximity to the ocean, ocean currents, topography, etc.
Explain how sediment changes as it moves from its source toward its place of final deposition.
Closer to final deposition = smaller, rounder, sorted
Explain how marble is formed.
Contact metamorphism
Confirm understanding of continental drift hypothesis, including the lines of evidence that supported it.
Continental-Drift Hypothesis: the idea that continents have moved and are still moving slowly across the Earth's surface. Evidence: - the fit of the edges of the continents - paleoclimate data (especially data on glacial deposits) - the distribution of climatic belts - the distribution of fossils on different continents - match of mountain belts between different continents
Explain what climate models predict for Earth's future.
Continued warmth of climate unless something is done.
List the top 3 most abundant elements in Earth's crust vs. the entire Earth.
Crust: oxygen, silicon, iron Entirety: iron, oxygen, silicon
Explain the distribution of shallow and deep earthquakes with respect to the different types of plate boundaries.
Deeper: convergent boundaries Shallower: divergent boundaries; transform boundaries
Explain how the source of a magma controls its initial composition.
Depending on what type of rock/crust/land melts, determines the composition of the rock that will eventually be formed. Partial melting of mantle forms mafic magma. Partial melting of continental crust forms felsic magma.
Discuss how stream discharge is calculated and why communities value this information.
Discharge (m3/s) = width x depth x velocity - Helps to predict hazards like flooding.
Draw a simple hydrograph showing how discharge would vary before, during and after a storm.
Discharge on y axis; time on x axis Streamflow gets higher with more precipitation.
Determine the best radioactive to use when trying to date a rock, given the half-lives of various isotopes and a guess for the age of the rock.
Divide age of rock by half-life of isotope.
List the age of the Earth and what this age is based on.
Earth is about 4.5 Ga years old. The age is mainly based on fossil records.
Describe multiple observations of recent climate change.
Earth is getting warmer with the rising concentration of greenhouse gases. Amount of precipitation changing in different areas. More extreme weather.
Describe the basis for the Geologic Time Scale.
Earth's history is divided up, mostly based on fossils (biological evolution). Earth was a hostile environment for most of its history - only evidence of primitive life in the early eons.
Explain the distribution of volcanoes and earthquakes and how that relates to the three boundary types.
Earthquakes and volcanoes tend to be found at the plate boundaries because of the movement of the plates. Magma coming out of the volcanoes is sourced from the melting of the asthenosphere.
Explain the various factors that control the discharge of a river.
Factors: - rainfall - groundwater input - amount of evaporation - melting snow or ice - vegetation - dams or other structures
Explain why, in general, average yearly temperatures decrease with distance from the equator.
Farther from the equator = sun is low in the sky, solar radiation travels farther to you
Explain how magma composition controls the explosiveness of a volcanic eruption.
Felsic magma causes larger volcanic eruptions because it is colder. Mafic magma causes more flowing volcanic magma because it is warmer, and there is less silica.
Discuss the steps communities take to prevent or adjust to floods.
Flood control: levee undermining, floodways Evaluating flooding hazard Flood-hazard maps
Explain how flood probabilities are calculated.
Flood probability = 1 / recurrence interval Example: for any given river, what is the probability that a 20-year flood will occur in 2018? -> 1/20 = 0.05 = 5%
Describe (and be able to identify) the difference between foliated and non-foliated metamorphic rocks, and provide examples of each.
Foliated rocks have horizontal indentations.
Explain how magma composition controls the type of volcanic eruption. Specifically, how do magma viscosity, gas content, and temperature relate to how explosive an eruption is?
Good lava: mafic, gases escape easily, low viscosity, lava flows smoothly, forms shield volcanoes and volcanic cones Bad lava: intermediate or felsic, gases cannot escape, high viscosity, explosive eruptions
Differentiate between hanging wall and foot wall.
Hanging wall = above fault Foot wall = below fault
Explain why oceans have a smaller yearly temperature range than continents and how the oceans influence global climate.
Heat capacity: water has a higher heat capacity; for the same amount of energy it will not heat up as much or cool down as much. Water moderates climates. Role of oceans: - Oceans trap heat and gases - Carry heat from equator to poles - Oceans take longer to warm/cool than ai
Explain how biochemical sedimentary rocks are formed, specifically chalk, limestone, and coal.
Living organisms cause minerals to be precipitated from solutions. Remains of dead plants/organisms (coal, limestone, chalk). > Coal: formed from terrestrial material > Limestone: formed from the accumulation of shells, coral, other marine life debris > Chalk: mineral calcite; forms under reasonably deep marine conditions
Pinpoint on a map or cross-section of plate boundaries where you are likely to find high or low viscosity magma.
Low viscosity = lava spreads out High viscosity = lava piles up in lava domes
Provide the 'type' rocks for oceanic and continental crust (basalt and granite), and comment on their differences with respect to cooling history, silica content, and density.
MORE RESEARCH
Explain what controls the magnitude of an earthquake.
Magnitude = a standard measure of the shaking and/or energy Magnitude is controlled by how much energy is released by an earthquake.
Explain the difference between earthquake magnitude and intensity.
Magnitude: a standard measure of the shaking and/or energy Intensity: a measure of the effects on people and buildings (damage)
Describe examples of modern-day divergent boundaries (Ex. Mid-Atlantic, Africa, Iceland).
Mid-Atlantic Ridge: ridge is high in area compared to the surrounding seafloor East Africa Rift Valley: divergent boundary beneath a thick continental plate
Explain how tsunamis form and at which plate tectonic settings they most commonly occur.
Most commonly occur at reverse faults (compression). Friction/tension caused at subduction zone flips out and water is displaced at a fast rate because of the energy released.
Explain why earthquake predication is essentially impossible.
Movement along fault zones is unpredictable and distributed among thousands of fractures.
Explain the Coriolis Effect.
Northern hemisphere = clockwise Southern hemisphere = counter clockwise If air moves south from the equator, which way will it be deflected as a result of the Coriolis Effect? to the east
Calculate the age of a rock given information on the radioactive isotopes within the rock (basically anything related to the clicker questions about radioactive decay is fair game).
Notes.
Sketch and interpret a graph of flood discharge vs. recurrence interval/yearly probability.
Notes.
Explain the difference in hazards associated with shield volcanoes vs. composite (strato) volcanoes.
Stratovolcanoes = tephra (volcanic ash, debris), lahars (volcanic mudflows), pyroclastic flows Shield = lava (lava flows, cinder cones)
Explain what kind of seismic wave typically causes the most damage, and why.
Surface waves tend to cause the most damage because they are closest to the surface.
Explain how rocks deform before and after fault movements that produce earthquakes.
The stress placed on a rock can cause it to stretch, squeeze, or shear.
Explain what creates Earth's magnetic field and why it is important for life.
The swirling outer core generates the Earth's magnetic field that behaves like bar magnets. Earth's magnetic field is important because it protects Earth (and its inhabitants) from harmful radiation: stray radiation from outer space, directs solar radiation from the sun (solar wind).
Explain what is meant by the terms 100-year flood, 50-year flood, etc.
This describes the flood recurrence interval. Measure of probability. Example: 100 years, have had 1 larger flood = 100-year flood
Describe the difference between high and low viscosity magma (what is viscosity?), and what controls the viscosity of a magma.
Viscosity = the property of a fluid that resists the force tending to cause the fluid to flow - High viscosity = does not flow well - Low viscosity = flows easily Viscosity is controlled by the amount of gases in magma.
Describe the major features of global atmospheric circulation, and how this circulation influences the general locations of humid/arid regions, cloudy/clear regions, and the direction of prevailing surface winds at different locations on the globe.
Warmer around belly, cooler around poles. - Cloud bands @ 60 degrees - more moisture/precipitation
Based on a sequence of sedimentary rocks, determine whether sea level rose or fell in order to produce this sequence.
Water rocks: shale, conglomerate, sandstone, limestone, chalk
Explain the difference between weather and climate, and provide examples of each.
Weather = conditions over short period of time (temperature, humidity, precipitation) Climate = changes in long-term averages of weather
Describe the likely depositional environment of the sediment that makes up a clastic sedimentary rock (based on its characteristics).
Weathering produces individual mineral grains > water carries it away > continue weathering into clay - Larger, sharper, less sorted means closer to mountains/cliff
Sketch the relationship between Earth and the sun to illustrate how the seasons vary by hemisphere.
When the hemisphere is tilted toward the Sun, it is summer in that hemisphere. When it is tilted away from the Sun, it is winter.