Exam IV Review Flashcards
Age of the earth
4.56 Ga
What distinguishes the mechanical layers? How do they relate to the compositional layers?
Lithosphere: rigid solid (crust and upper mantle, including Moho)
Asthenosphere: weak solid (mantle)
Outer core: liquid (core)
Inner core: solid (core)
The lithosphere is primarily oxygen/silicon/aluminum/magnesium, the asthenosphere is primarily oxygen/silicon/magnesium, the outer core is mostly liquid iron, and the inner core is mostly solid iron.
Which are most appropriate units for plate tectonic motion, cm/yr, m/yr, km/yr?
cm/yr (1-15 to be exact)
What is the difference between a theory and a hypothesis?
Hypothesis: An explanation for observations to be tested (may be supported, not confirmed)
Theory: An explanation for observations that have been tested numerous times and is supported by evidence
Most abundant mineral in crust of the Earth
plagioclase feldspar
What are the three rock types, what differentiates them, and what are their rock forming processes?
1) Igneous: made from magma
2) Metamorphic: recrystallizing in solid state
3) sedimentary: rock fragments/dissolved rock components compacted on surface
Common examples of igneous, sedimentary, and metamorphic rocks
Igneous: Obsidian, tuff, scoria, pumice, breccia, granite, diorite, gabbro, rhyolite, andesite, basalt, “porphyritic ____”
Sedimentary: coquina, fossiliferous limestone, oolitic limestone, chalk, rock salt, gypsum, coal, conglomerate, breccia, sandstone, chert, mudstone, shale
Metamorphic: slate, phyllite, schist, gneiss, quartzite, marble, amphibolite, hornfel
What is the concept of uniformitarianism; what are simple examples of its application?
Definition: processes we see active today were active in the past and explain analogous characteristics observed in rocks
ex: crossbedding=sand dunes, poor sorting and striations=prolly glaciers?
Difference between magnitude and intensity
Magnitude: measure of energy
Intensity: measure of the effect on humans
Recognize synclines vs. anticlines in photos or diagrams
1) anticline (like an A, old rocks on peak)
2) syncline (like a V, young rocks in pinched bottom)
Remember: old in middle is anticline, young in middle is syncline
Recognize faults: normal, reverse, left-lateral and right-lateral strike-slip in photos or diagrams
normal (hanging wall block goes down, foot wall block goes up)
reverse
thrust
strike slip
Stresses responsible for folds, normal faults, and reverse faults
Normal faults produced by divergent/extensional stress
Reverse/thrust faults produced by convergent/compressional stress
be able to interpret the relative ages of two geologic features in a photo or diagram
practice
The geologic time scale: know the order of the three eras of the Phanerozoic eon and the general term for the time before that.
Phanerozoic eon’s eras: Paleozoic, Mesozoic, Cenozoic
Time before that: Precambrian
Eon of most of the rocks at the core of the Black Hills
Proterozoic
Era that the Appalachian mountains were built
Paleozoic era
Which came first, uplift of the Rockies, including the Black Hills, or deposition of the sedimentary rocks in the Badlands?
Within the Cenozoic Era, Paleogene period: Rockies/Black Hills are uplifted…then their shedded sediments + ash from distant volcanos form Badlands
Epoch of glaciations and name of most recent glaciation
Pleistocene epoch (Quarternary period, Cenozoic era)
Wisconsin Glaciation, 21 ka
Epoch used to describe time since the end of the ice ages
Holocene epoch
Recognize photos of clear examples of different types of mass movement highlighted in class
rock fall, rock slide, debris flow, mud flow, creep, slump, solifluction, lahar
Three kinds of stream channel patterns: what makes them different? where do they occur in stream systems?
straight: confined by topography/bedrock in mountain stream systems
braided: smaller, weaving channels that clog themselves with sediment, found near mountain fronts
meandering: large loopy bends across floodplains
Recognize in photos, and understand the origins of, point bars, cut banks, natural levees, alluvial fans, deltas, terraces, and ox bow lakes
point bars: inner sides of bends
cut banks: outside of bends
natural levees: created when a stream floods
alluvial fans: created when a stream gradient decreases
deltas: created when stream hits still water
terraces: stream floods, creates floodplain, then starts to down cut and create stream terraces
oxbow lakes: meandering stream cuts through a meander neck (cutting off its loops)
What distinguishes a glacier from a permanent snow or ice field?
In a glacier, the burden of additional snow without much seasonal melting forces crystals to compact into thick masses that flow under their own weight
~maximum thickness of North America’s past continental ice sheets?
3,000 m/10,000 ft thick
Ice shelves vs sea ice
Ice shelves source from ice sheets that have extended over onto the ocean
Sea ice is ocean water that has frozen
Be able to recognize different types of glaciers shown in class.
Mountain: cirque, valley, piedmont (think alluvial fan), ice caps (not topographically confined)
Continental: ice sheet, ice shelves (basically ice sheet but over the sea…NOT sea ice)
What percentage of fresh water is in glaciers? What percent of that in the two main ice sheets?
70% of fresh water is in glaciers
85% of that in Antarctic ice sheet
10% in Greenland ice sheet
What is the equilibrium line? what are the zones on either side, and what distinguishes them?
the line above the zone of accumulation and below the zone of ablation
accumulation: more snow/ice falls than melts per year
ablation: more snow/ice melts than falls in a year
Processes of glacial advance and retreat
advancing: zone of accumulation overpowers zone of ablation (when flow exceeds melting)
retreating: zone of ablation overpowers zone of accumulation
- glaciers don’t move backwards, they just stop flowing or melt faster than they flow
About how fast do glaciers usually move?
10-300 m/yr
What are the two ways that glaciers move?
Internal flow + basal sliding
What is distinctive about glacial deposits?
It transports material of all grain sizes, making for distinctly poor sorting
Two ways glaciers erode, and the nature of sediment produced by both
Abrasion - creates fine sediment
Plucking - creates course sediment
What makes drumlins different from roche moutonnée?
Bedrock vs sediment
Steep vs gradual down flow side
Four kinds of moraines?
lateral medial end recessional ground
Be able to identify the following glacial features discussed in class on photographs: lateral moraine, medial moraine, end moraine, drumlin, roche moutonnée, cirque, tarn, horn, hanging valley, arete, kettle
lateral m: on the sides
medial m: in between multiple glaciers
end m: at the end, obvi
drumlin: sediment hill thingy
roche moutonne: bedrock hill thingy
cirque: glacier that’s carved the bedrock into a bowl
tarn: meltwater lake in cirque
horn: sharp peak carved by glacier
hanging valley: created when a smaller, shallower glacier intersects with a bigger, deeper one
arete: bedrock ridges
kettle lake: chunk of ice breaks off and melts
Be able to determine ice flow direction from a photo or diagram of a drumlin or roche moutonnée
Remember:
rouch moutonee: bedrock, steep on the downflow side
drumlin: sediment, gradual on the downflow side
What is an esker (from reading)
A ridge of sorted sand/gravel that snakes across a ground moraine
Sediment was deposited in subglacial meltwater tunnels
What kind of streams flow from glaciers
braided streams (outwash)
Significance of pluvial lake
show cooler/wetter climage of ice ages + location of old glaciers bc these are lakes in now arid regions
Name of highlighted pluvial lake and highlighted meltwater lake, and what kinds of lakes occur all over eastern SD and Minnesota?
Pluvial lake (ice age lake now in arid area): Lake Bonneville in Great Basin
Meltwater lake: Glacial Lake Agassiz
-kettle lakes (prairie potholes)
What is loess, and how does it relate to glaciers?
It’s fine sediment/silt deposited by glaciers into braided streams, picked up by wind, and then deposited elsewhere.
How does the land surface respond when a continental ice sheet melts away? (uplift, subsidence, or stays the same?) (from reading)
Gradually, the surface rises back up (aka post glacial rebound). The lithosphere/asthenosphere rises up at millimeters per year, so it takes years for ice-depressed continents to rebound.
Difference between zone of saturation and the unsaturated zone, and why it matters
saturated zone is where all available voids are filled, sitting below the unsaturated zone.
Wells can only pulls water form the saturated zone; if they tried to pull the water from the unsaturated zone, they’d only pump up air (think of a slurpee)
What is groundwater
water occupying void spaces in the solid earth in the saturated zone (where all available voids are filled)
How is the water table defined?
the surface at the top of the saturated zone
How does groundwater flow relative to contours of the water table?
Perpendicular to contour
Top three overall water uses in U.S. (in order)
#1 thermoelectric power #2 irrigation #3 public supply
What % of U.S. public water supply from groundwater?What % of South Dakotans get their water from groundwater?
39% of US public water supply is groundwater
78% of South Dakotans get water from groundwater
Porosity vs. permeability?
porosity: amount of open space in a rock/sediment
permeability: ability of a rock/sediment to transmit water
What is an aquifer
a rock/sediment unit from which groundwater can be extracted
What kind of rocks or sediments makes the best aquifers?
sand, sandstone, limestone, well sorted gravel
Basics of two highlighted aquifers in South Dakota discussed in class
Big Sioux: east river, in glacial “outwash” and other stream sediments
High Plains: in Miocene-Pliocene stream deposits, south-central part of state, extends into Texas, severely overdrawn
Clay & shale has have high porosity; why can’t these make good aquitards?
They have high porosity but LOW permeability because their pore space is small
What is a confined aquifer?
an aquifer with a capping, confining layer
What creates a perched aquifer?
a shallow aquitard of limited extent
What is the zone of recharge?
where the water enters the aquifer
How does a cone of depression form, and what are the potential consequences?
when the hydraulic gradient changes directions and contaminants are transported into groundwater (wells are drilled where the gradient is declining instead of where it is rising)
Difference between stalactites & stalagmites
stalactites: deposited from ceiling
stalagmites: deposited on floor
What term describes a landscape created by groundwater dissolution?
karst/tower karst
In what rock type does groundwater most commonly create a distinctive landscape?
limestone
How do sinkholes form? and where, in the U.S., are they most abundant?
Dissolution creating caves causes collapse at the surface
most abundant in Florida….?
% of earth covered by water? What % of that is oceans?
71%
97% of that is oceans
% salt in saltwater
3.5%
Relationship between wavelength and depth at which waves “feel bottom” and term for this depth
The depth is called the wave base and is about 1/2 a wavelength (one crest to another)
displacement of water particles happens in orbital motion
How does sediment get transported parallel to shore?
via the longshore current
How do waves refract? Effect on headlands and coves
Waves slow as they reach shore. some parts are closer to the shore than others so they bend/refract to approach more directly
Energy lessened on coves; energy concentration on headlands straightens coastlines
Difference between longshore current and longshore drift
The current is the motion of the crashing waves along the land
The drift is the moving sediment
How do we attempt to control longshore drift?
Groins (curved on one side), jetties (straight on both sides), and breakwaters (curved on both sides)
Recognize in photos/diagrams spits, baymouth bars, barrier islands, marine
terraces, tidal deltas
sand spit: longshore current comes from the side the sand spit is connected to
baymouth bar: comes form both sides
barrier islands: just think of the east coast islands
marine terraces: mountains/shores/cliffs with levels cut into them
tidal deltas: sandy, watery, grassy mess
Be able to interpret the direction of longshore current by examining sand spits and jetties/groins
Look for the direction of accretion
Have a basic understanding of the cause of tides (why two a day?)
Caused by the tide generating force (gravitational and centrifugal forces)
Two high and low tides; once when Moon is on same side and once when Moon is on opposite side
In general terms, how much sea level changed in the last century? Since the last
ice age?
20 cm since 1900
100s of meters since last ice age
In what ways does future sea level rise pose a threat? (two general ways)
1) some areas will become submerged
2) increased impact of storms
Recognize and understand the formation of submergent and emergent
landscapes.
submergent: form when sea level rises and submerges landscaped carved above sea level (estuaries and fjords)
emergent: wave erosion + sea level drop/land surface rise (marine terraces)
What country, where, is most threatened by sea level rise?
Maldives (Indian Ocean)
What officially defines a desert, climatologically?
<25 cm (10 in) of rain per year
How many U.S. states have deserts?
12
% of land in deserts
25% of land surface is desert
Controls on global wind patterns
moisture in air
whether air is rising or sinking
Five different causes of deserts, and highlighted examples
descending air at 30 degrees: Subtropical (Sahara)
moisture lost over mountains: rain shadow (Great Basin)
moisture lost over great distance: continental interior (Gobi)
cold coastal currents, warm air above prevents rising: coastal (Atacama)
cold air holds little moisture + descending air + high pressure?: Polar (antarctica)
How rising vs. sinking air affects atmospheric moisture and precipitation vs. dry
cells of rising/sinking air affect where places are dry wet
rising air carries water and precipitates it as it rises/shrinks
sinking air is dry and carries no water for precipitation
Why are there deserts at 30 degrees north and south?
Because there are cells of sinking air there that are both dry and warm
Where is the driest place on Earth (non-polar)?
The Atacama Desert in Chile/Peru
On what side are dunes steepest? (upwind or downwind)
downwind
Be able to recognize barchan, and transverse dunes in pictures or diagrams
Barchan (shaped like a parabola/horseshoe)
Transverse (perpendicular to the wind, more long looking)
Be able to determine wind direction based on pictures of dunes
lol good luck
Playas
evaporated desert lake
The role of water in desert landform formation (and examples)
main landscaping agent
often in brief but intense rainfall events
playas, alluvial fans, mesas and buttes, cliff retreats
Material that accumulates to make oil (and natural gas) vs. coal
buried algae and plankton (around.5 mm diameter) accumulated in a basin
Under what conditions does natural gas form? (relative to oil)
What is natural gas made of mostly?
at higher temperatures, associated with crude oil deposits
it’s mostly methane, CH4
Four things necessary to have an economic oil deposit
source, reservoir, seal, and trap
Where is there more high-quality (more efficient, less polluting) coal being mined,
Appalachians or Wyoming?
I think it’s Wyoming?
What is the leading renewable energy technology?
wind power
Fossil fuel resource that the U.S. is the leader in reserves? (but not the leading
producer)
Coal
Two fossil fuel resources that the U.S. is a leading producer, but not the leader in reserves?
Oil and natural gas?
Recent changes in U.S. electricity production. one declining technology, two rapidly growing (using fairly general categories)
Coal is declining
Natural gas and renewables are increasing
What kinds of folds can make traps for oil/natural gas? (2)
domes and anticlines
What is the process of “fracking”?
A means of acquiring shale oil and natural gas by creating artificial porosity to free oil from fine-grained shale
Two states that have greatly increased oil production by fracking
North Dakota + Texas?
Negatives of tar sands as a fossil fuel resource
- destructive mining practices
- requires energy and water to process
- more CO2 released in processes
What are cheapest energy technologies for new electrical power plants?
wind and solar
What is special about energy production in Iceland?
25% relies on geothermal energy (mid ocean ridge AND hotspot)
What is the range of concentration factors of important metals? (two highlighted
elements and concentration factors from lecture)
Aluminum: 3-4
Gold: 4,000-5,000
Highlighted way in which igneous processes create ore deposits
igneous processes: settling of minerals in magma chamber
hydrothermal processes: hot fluids concentrate elements in or near intrusion
How do placer deposits form?
in the beds of streams/lakes/channels
Important material quarried for gravel and dimension stone near Sioux Falls
(southeast South Dakota)
Sioux Quartzite
State whose oil production has declined substantially in recent decades
Alaska
Rock that goes into making cement
Limestone
What greenhouse gas is produced by cement production, and about how much
of it comes from this source?
CO2 (carbon dioxide), about 5-8%
Astonishing fact presented in lecture about cement production in another country
China used more cement in 2011-2013 than the US used in the entire 20th century
What are the differences between unidirectional changes, physical cycles, and
biogeochemical cycles?
Unidirectional changes can’t be reversed
Physical changes happen on a tangible observable level
Biogeochemical cycles happen at the molecular level over great distances
Know highlighted examples of each of the types of global change
Unidirectional: planetary differentiation
Physical: supercontinent, rock
Biogeochemical: hydrologic, carbon
Recognize examples of positive and negative feedback (if I give you a new example, recognize it as positive feedback or negative feedback)
Positive: self-reinforcing/promoting…a thing happening makes the thing happen more, and more effectively in the future (dam failure)
Negative: self-defeating (homeostatic thermoregulation)
What makes a gas a greenhouse gas?
If it can trap long wavelength radiation in atmosphere
Most abundant greenhouse gas
water vapor (but carbon dioxide is the most impactful)
Understand the difference between climate and weather
Climate is the average and range of weather conditions for region
Weather is just what’s happening at a select point in time
aquitard vs aquifer
aquifer: rock that holds the water
aquitard: Layer with low permeability
