Geology
GEOS 2104 – Final study guide
I. Terms to know (you will not need to write out definitions, but known the meaning of the terms so you can use them and answer questions about them). Your non-top Hat final will be pulled entirely from these terms, so know them! The Top Hat questions are essentially a selection from this list.
Intro and planet formation
Big Bang red shift nucleosynthesis
nebula protoplanetary disk planetessimals
chondrite meteorites planetary accretion geomagnetic dynamo
iron meteorites differentiation core
inner core outer core refraction
P-wave S-wave P-wave shadow
S-wave shadow
Plate Tectonics
peridotite mantle convection
distillation partial melting sea-floor spreading
oceanic crust continental crust subduction zone
volcanic island arcs plate tectonics hypothesis
theory paleomagnetism magnetic lineations
lithosphere asthenosphere mantle convection
plate boundary mid-ocean ridge rifting
trench subduction zone Ring of Fire
strike-slip boundary oceanic transform passive margin
collisional plate boundary Wegener Glacial striations
Glossopterus Geosynclines
Minerals
Silicate silica tetrahedron crystal lattice
Mineral definition atomic structure Cation
Anion Coordination polyhedral Oxide
Carbonate Common mineral family decoder list
Igneous rocks
intrusive igneous rock extrusive igneous rock felsic
mafic granite basalt
dike sill pluton
batholith volcanic ash lava flow
viscosity shield volcano strato (composite) volcano
rhyolite andesite diorite
differentiation
Sedimentary rocks
physical sediment chemical sediment fluvial erosion
erosion lithification compaction
cementation deposition talus
clay minerals conglomerate sandstone
shale biochemical sediment limestone
chert evaporite organic sediment
sediment sorting cross bedding bedforms
Halite Gypsum
Metamorphism
metamorphism diffusion foliation
metamorphic grade slate phyllite
schist gneiss migmatite
geothermal gradient Index minerals Facies
Weathering
weathering Delta oxidation
mass wasting hubris floodplain
meandering avulsion debris flow
landslide acid-mine drainage hydrolysis
physical weathering chemical weathering
Geologic time
Geologic Timescale relative geologic time absolute geologic time
stratigraphy superposition original horizontality
faunal succession radioactive decay isotope
half-life Absolute dating Relative dating
superposition Uniformitarianism Hutton
Relative dating Lateral continuity Cross cutting relationships
Role of fossils in correlation
Geological time scale
Relative order/sizes of Eons, Eras, Periods, Epochs, Stages
Ages of start of Proterozoic, Paleozoic, Mesozoic and Cenozoic Eras
Breaks in deposition (unconformities)
Angular unconformity
Disconformity
Non-conformity
Geology of Virginia
Blue Ridge Piedmont Valley and Ridge
Pangaea Rodinia Alleghany Plateau
Coastal Plain Wilson cycle Grenville
Appalachian collisions Taconic Radon
Deformation and mountain building
thrust fault folding stress
ductile deformation brittle deformation strain
earthquake epicenter focus
elastic rebound seismograph magnitude
Normal fault Strike-slip fault Joints
Faults Fractures Foliation
Is foliation the same as bedding? Strike
Dip
Earthquakes
P waves S waves surface waves
tsunami forecast probability map Earthquake hazards
precursor liquefaction Forecasting
Prediction Building structure types that are good for seismic resilience
Building types that are bad for seismic resilience
Geologic settings that are favourable and unfavourable for building foundations in seismic zones
Seismic wave frequency and impact on structures
Moment magnitude scale
Scale factor for 1 magnitude of increase
Basic physical parts of moment magnitude equation, (NB: not precise factors, so identify equation in words and not numbers)
Groundwater
groundwater porosity permeability
aquifer aquiclude unconfined aquifer
water table saltwater intrusion confined aquifer
artesian well Darcy’s Law
Soils
Soils agriculture classification (sand vs silt vs clay) N-P-K
Leaching O-A-E-B-C horizons Pedon
Role of time Soil thicknesses by latitude USCS
Grain size Soil plasticity Role of clays
Atterberg limits concept
Landslides
Normal stress Shear stress Friction
Pore pressure Mohr’s circle Angle of repose
Oversteepening Adding mass Dynamic triggering
Liquifaction Planes of weakness Recurrence in same places
ii - This is not a list of exam questions, but being able to answer these on a basic level means you will know everything you would need to know. These are questions you should be able to answer to yourself to prepare yourself, or as part of a group.
Introduction and planet formation
What is the evidence for the Big Bang?
What does the Big Bang theory really explain?
Explain the history from the Big Bang to formation of the Solar Nebula and the role of gravity.
Why are the planets close to the sun (4) rocky, while those farther away are gaseous with rocky cores?
How do chondrite meteorites form and what they tell us about the age and composition of the original Solar System material (pre-planets)?
Earth structure
Be able to explain what the major concentric layers of the Earth are, including whether they are liquid or solid and what they are made of, plus anything else special about them.
How do seismic waves help define the inner structure of the Earth? Explain where the seismic waves come from, why some are unable to transmit through liquid, why they curve in the Earth, and how this creates "shadows".
What is the difference between the composition of the core and mantle? What does the mantle have, that the core doesn't, in terms of elements?
Why did the Earth's core form? What is important about this in regards to the abundance of different elements on Earth? (i.e. how common is Fe?)
How do iron and pallasite meteorites form and what they tell us about the process of planetary differentiation?
How is the Earth's magnetic field created and what does it have to do with the core? Why does this support the model of the inner and outer core being different phases (i.e. liquid vs. solid)?
Explain how the Moon formed from the Earth.
Plate tectonics
Explain the key differences between oceanic and continental crust in terms of thickness, density, and composition.
How does the oceanic crust form from the mantle? Why does the mantle melt? How much of the mantle melts? Where is oceanic crust made and how does it lead to sea-floor spreading?
How is it possible for the mantle to convect and transfer heat, when it is still a solid?
Why are the continents higher than the sea floor? Is it just that water pools in the oceans, or is the sea floor significantly and systematically a different elevation? Why? What adjusts to the differential weight from continental/oceanic crusts?
Where does continental crust form? What melts to produce continental crust and how does it accumulate above into volcanoes? How do these pieces or slivers of crust then get amalgamated into continents?
What is the timeframe of creating continental crust and how does it differ from oceanic crust? Which is old, and which is young?
How is plate tectonics the "unifying" theory of geoscience?
Why did it take so long (until the 1960s) for plate tectonics to go from a loose hypothesis to a theory?
Explain the data that Wegener had for his hypothesis of continental drift and the data that were needed to elevate the idea to a scientific theory in the 1960s.
In addition to data, how else were Wegener's ideas limited? What was he really missing? How does this make his career story different than, say, Charles Darwin's?
Explain how the magnetic signature of oceanic basalt can be used to map out the age of the sea floor. Why do rocks get magnetized and what are the alternating signals (positive and negative) due to? How come the signature ends up as lineations or stripes on the sea floor? Which direction do lineations get younger relative to the mid-ocean ridge?
What is the difference between lithosphere and asthenosphere based on? How does the lithosphere differ from the crust, and which of these are the "plates" in plate tectonics?
About how many plates are there on Earth and about how fast do they move relative to each other (on average)?
What are mid-ocean ridges like? Explain some of their characteristics and what happens at them.
What are subduction zones like? Explain some of their characteristics and what happens at them.
What types of plates subduct and which don't?
How old can oceanic lithosphere get? What does this mean for recycling of oceanic lithosphere and where does this occur on Earth?
What kind of boundary exists between North America continental lithosphere and the Atlantic oceanic lithosphere? Where is the closest active plate boundary from our location?
Why do secondary plate boundaries, like strike-slip and collision, exist on Earth? Why can't it all just be mid-ocean ridges and subduction zones?
What kind of motion occurs at a strike-slip plate boundary, and what is an example of one?
Deformation and mountain building
Why are continent collision and mountain building important processes for the Earth?
What is the origin of the Alpine-Himalayan mountain chain? What continents are colliding and what has been the tectonic history?
Are all mountains on Earth formed by continent collision?
Why is deformation an important process for continental crust?
How does the type of strain during deformation differ among the types of plate boundaries?
Describe the processes that occur in a fold-thrust belt. In addition to deformation, how does the continental crust change as a result (i.e. in geometry)?
Earthquakes
What factors control the nature of deformation, and specifically what kind of deformation results (i.e. brittle vs. ductile)?
How are earthquakes a side-effect of plate motion, not a primary process or a cause of faulting?
Where are earthquakes distributed on Earth and why can they occasional occur within plates?
What is the source area of an earthquake shaped like (i.e. not a point)?
Explain the theory of elastic rebound and how it explains rare, sudden movements on faults while the plate motions are continuous in the background.
How are earthquakes located?
What is earthquake magnitude based on and why is it calculated using a logarithmic scale?
How does the frequency of global earthquakes vary with earthquake magnitude?
What is an active fault and are all faults active? Where can dead faults be found?
Why are so many more people killed by earthquakes today than hundreds of years ago? Provide an example to support your idea.
How does the intensity of shaking change with distance from an earthquake source and where is the intensity (and damage) most intense? At long distances, what type of seismic wave causes most of the shaking and damage?
How does the ground affect shaking intensity during an earthquake and what kind of ground (e.g. bedrock or soft sediment) is more stable?
Why do many earthquakes in global south countries cause more fatalities than in the U.S.?
What kind of building is the most stable to be in during an earthquake? Which is the worst?
Can earthquakes be predicted using precursors? How can earthquakes be forecast and how good are these forecasts? What are forecasts useful for, even if they are not accurate enough to trigger evacuations?
What are earthquake early warning systems and do they really help?
How are tsunami created during earthquakes? Explain how tsunami waves are different from normal beach waves and why they are considered a "surge" and last so long.
Minerals
What are some of the different properties that are used to describe and differentiate minerals?
Be able to explain why atomic structure is important to defining a mineral, and give an example of different minerals that have the same composition but different atomic structure. What is this called?
How is a mineral's atomic structure reflected in its properties?
What other factors of a mineral's chemistry can affect its physical properties?
What controls which elements from the periodic table will join together to form minerals?
Igneous rocks
How are igneous rocks made?
What is the difference between intrusive and extrusive igneous rocks, in terms of where they form, but also their appearance?
Where and how are rocks melted in the crust, to form new igneous rocks?
How are igneous rocks classified?
What are some forms of igneous intrusive rocks, and what do their geometries say about the physical processes of intrusion?
How does volcanic ash in a column differ from smoke from a fire?
How does volcanic eruption style depend on viscosity, and what controls viscosity of magma?
Why do mafic magmas form shield volcanoes and result in "effusive" eruptions?
Why are eruptions of stratovolcanoes so explosive? Why are these volcanoes steep sided?
Where tectonically do the different types of volcanoes occur?
Under what conditions are erupted ash columns or ash deposits dangerous to people?
What are the characteristics of pyroclastic flows and why do they occur?
What is the kind of rock that is deposited by a pyroclastic flow?
How is the relative size of an eruption characterized, or by what metric are they compared?
The largest volcanic eruptions are invariably caused by what kind of event?
Be able to explain how moderate eruptions and specific hazards like flows can result in thousands of fatalities, yet the truly giant eruptions (calderas) are capable of destroying entire civilizations or even causing extinctions.
What is the typical sequence of a caldera eruption, in terms of how long it lasts, how it ramps up, and what occurs during the climax?
What are the two ways in which location may be taken into account to assess volcanic hazards?
Can volcanic eruptions be predicted? What kinds of precursory observations would be used to do this?
Metamorphism
Why do minerals change (metamorphose) into new minerals? What factors cause this, and what does equilibrium of the mineral have to do with it?
How is it possible for atoms to rearrange in the solid state to form new minerals via metamorphic reactions? What process allows this to occur?
How do pressure and temperature change with depth in the Earth's crust? Which of these changes instantaneously and uniformly from spot to spot?
What does an increase in pressure actually do to force metamorphism (i.e. at the atomic level)?
What does an increase in temperature do to force metamorphism (i.e. chemical reactions)?
Be able to explain how certain minerals have stable "regions" of temperature and pressure (i.e., grade) and thus can be diagnostic of the depths they formed at, like organisms can be diagnostic of ecosystems. Know an example or two.
How do metamorphic rocks change (i.e. layering, size of crystals, foliation) with increasing "grade" of pressure and temperature?
Why is it useful to be able to estimate how deep a metamorphic rock was that is now at the surface? What can this tell us about collisions and mountain building, for example?
Sedimentary rocks
Why are sedimentary rocks important?
What are the steps in making sedimentary rocks?
What happens during burial of a sediment, that transforms it into a sedimentary rock?
How are physical sedimentary rocks classified?
How are chemical sedimentary rocks classified?
What are the three ways of making chemical sedimentary rocks?
Be able to explain how both rock type (e.g. for chemical sedimentary rocks) and features of physical sedimentary rocks can be diagnostic of the environment in which they were deposited.
What changes occur to physical sediment as the distance and duration of erosive transport (e.g. by water) increase?
What are examples of other sedimentary features that are helpful in determining the depositional environment of a sedimentary rock?
Geologic time
How is the relative order of geologic events in a given suite of rocks determined using the geometry and structure of sedimentary rocks?
How does the resolution of the Geologic Timescale change going back in time?
Why was the original Geologic Timescale organized by odd names, rather than numbers? Where did the names come from?
In what two ways is the timescale based on relative dating incomplete?
What features were critical for identifying gaps in the rock record, as well as for correlating sections of rock that are not connected (i.e. around the world)?
Why is radiometric dating performed on minerals specifically, not necessarily rocks?
What happens to atoms when they radioactively decay? (e.g. think of what happens during beta decay; how does the resulting "daughter" atom differ from the original "parent" atom?
Why is "half-life" a good approximation for how a radioactive isotope decays over time?
Why is radiometric dating better suited to igneous rocks than for physical sedimentary rocks?
Virginia Geology
Explain the tectonic history of eastern North America, including collision and rifting and formation of the Appalachian Mountains in Virginia
What happened in Virginia after the Appalachian mountain building episode?
Groundwater
Be able to describe the hydrologic cycle, including the reservoirs and their relative sizes and the main inputs and outputs to each (the process, not the rate of flux). No need to memorize numbers, but what are the major parts/players?
Is water in the hydrologic cycle created, or just transferred? Could there be any situation in which it's created?
Why is most of the water in the hydrologic cycle liquid?
How does the total volume of water in the hydrologic cycle vary with time? What about the reservoirs; are the constant volume? Under what conditions can the volume of reservoirs change? (be able to give an example)
Be able to explain how heat and salinity (both factors that control water density) drive 3D ocean circulation like convection currents. How does this pattern then get affected by wind, and then melting sea ice?
Geography of continents to shape the major ocean currents? What is the turnover time for the oceans due to this mixing?
How do geologic structure, rock type, and topography result in things like artesian wells or oases, or situations in which groundwater can travel very far from the site of infiltration in the ground to where it is removed?
How is it that the deep groundwater often used by communities in arid locations can be considered "old", "relict", or even "non-renewable"?
Describe the different types of contaminants to groundwater, how contaminants move, and how they are removed.
Why is water often considered the most important natural resource?
Where do people living in arid and semi-arid regions generally get their water from?
What are example rock types that make up good aquifers, versus aquicludes?
How fast does groundwater move?
Why is the top of the unconfined aquifer often somewhat parallel to the surface of the Earth?
What is Darcy’s Law?
Soils
How do engineers describe soils?
What physical property controls how coarse-grained soils behave
What physical properties control how fine-grained soils behave? Why?
Landslides
In physical terms, why do slopes fail?
What human actions can cause landslides?
What natural dynamic triggers can cause landslides?
What role does pore fluid pressure play in controlling landslides?
What conditions can change pore fluid pressure?
