Exam III Review Flashcards
Age of the earth
4.565 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.
How fast do plates move?
1-15 cm/year
Types of plate margins and most highlighted examples of each
Convergent: north american plate meeting pacific plate
Divergent: mid atlantic ridge, east african rift
Transform: fracture zones around mid atlantic ridge
In what tectonic environment are volcanic arcs formed?
Convergent boundaries/subduction zones
Mariana Islands, Cascades, Andes
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
What are the four components of the definition of a mineral used in lecture?
1) solid
2) naturally occurring
3) crystalline structure
4) definable composition
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, hornfels
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?
What group of minerals is a product of weathering and common in soils?
Clay minerals (Kaolinite?)
Key nutrients in soil
Nitrogen, Phosphorus, and Potassium
How is metamorphism different from igneous processes?
It recrystallizes in the solid state, not the liquid state
How does foliation orientation relate to directions compressional tectonic stresses?
Foliation orientation forms perpendicular to tectonic stress
Epicenter vs focus (hypocenter)
Focus/hypocenter: the place inside Earth’s crust where an eq originates
Epicenter: The point on the Earth’s surface directly above the focus
Difference between magnitude and intensity
Magnitude: measure of energy
Intensity: measure of the effect on humans
how much more energetic is an earthquake 1 magnitude than another? Difference of 2? etc
32x increase per magnitude (going up twice would be 1000x, 32 x 32)
What does the S wave shadow zone tell us? why?
that s waves can’t pass through the core/liquid/fluid because of their lower velocity/shear motion??
What does seismic tomography tell us?
it creates a 3D image of variations in seismic-wave velocities within the earth to understand where waves will speed up and slow down (with anomalies of course)
Types of Faults (identify in photos)
normal (hanging wall block goes down, foot wall block goes up)
reverse
thrust
strike slip
Stress versus strain
strain: change in object’s shape in response to application of stress
stress: force applied to a surface which causes strain/deformation
Brittle vs plastic deformation
brittle: cracking and fracturing (faults and joints)
plastic: becoming flattened or elongated without cracking/breaking (folds and foliation)
What are strike and dip?
Strike: a line where a geologic plane intersects a horizontal plane
Dip: the angle at which the plane enters the earth
What do plunging folds look like on a map or aerial photograph?
looks like flattened fold patterns on surface (if you can see folds on a geologic map, it’s plunging)
Sheep Mountain, Wyoming
What kind of stresses cause folding?
Reverse/thrust faults, convergence
Recognize the five kinds of folds
1) anticline (like an A, old rocks on peak)
2) syncline (like a V, young rocks in pinched bottom)
3) Monocline: one sloping surface between the horizontal
4) Dome: upward focused on a point
5) Basin: downward focused on a point
Recognize map patterns of synclines and anticlines based on ages of rocks and/or strike and dip symbols
Remember: old in middle is anticline, young in middle is syncline
study strike and dip maps
Stresses responsible for normal vs reverse faults
Normal faults produced by divergent/extensional stress
Reverse faults produced by convergent/compressional stress
How are joints and faults different?
Joints: planar fractures in rocks along which no movement has taken place, caused by divergent tension?
Faults: fractures/break in rock along which movement has taken place
What kind of structure is responsible for the Basin and range landscape in the western US?
horsts and grabens (ranges and valleys)
Tectonic divergence/extension
What are thrust faults? Where are fold and thrust belts found in the US (two examples)
Thrust faults are reverse faults with a low angle
Fold and Thrust belts: form during continental collisions and subduction zones
Ex: Appalachians, Rockies, Black Hills?
What does the term orogeny mean?
Orogeny: mountain building event
What modern technology can track deformation in ‘real time’? at what rate?
GPS (mm/year)
Difference between relative and numerical age
relative: describes ages of features with respect to another but doesn’t directly involve a numeric age
numeric: specific age dating based on radioactive decay
highlighted techniques other than radiometric dating that yield numerical ages
tree rings, varves (lake beds), annual ice layers in glaciers
principles used to document relative age and correlation of geologic units (there’s 6)
"principle" of superposition "" cross cutting relationships ""inclusions "" original horizontality "" lateral continuity "" fossil succession
be able to interpret the relative ages of two geologic features in a photo or diagram
practice
the geologic time scale: knowing geologic time scale elements requested in class (look at photo)
look at photo, cuz I’m struggling lol
Ugh, now I gotta pull up that photo
Yeah. Sorry bout that lol
Three kinds of unconformities (recognize in pictures)
angular unconformity
nonconformity
disconformity
How are unconformities interpreted?
They’re interpreted as breaks in the geologic record; missing time
Concepts of radioactive decay, parent/daughter, half/life
radioactive dating: utilizes time dependent decay of radioactive isotopes
parent: isotopes of elements that are unstable and undergo spontaneous change, releasing energy
daughter: the new isotope of a new element created by the decaying parent
half life: the time required for 1/2 of a quantity of an isotope to undergo decay
1/2, 1/4, 1/8
know parent-daughter element pairs highlighted in class that are used for age dating
K > A
C > N
U > Pb
eon during which most continental crust formed
Archean eon
general term for old cores of continents
cratons
eon of most of the rocks at the core of the black hills
Proterozoic eon
era and period that life diversifies and there was improved preservation of fossils, and the name given to this “event”
Era: Paleozoic
Period: Cambrian
Cambrian explosion
era that the Appalachians were built
Paleozoic era
era in which the rockies, including the black hills, popped up (and name of orogeny)
Cenozoic era (laramide orogeny)
in what era and period did a great inland sea last cross most of South Dakota?
Mesozoic era, Cretaceous period
what event frequently marks the boundaries between units of the geologic time scale?
extinctions
highlight mass extinction, timing, and cause
K-Pg extinction (end of Mesozoic, start of Cenozoic era) 66 Ma
meteorite impact in Yucatan peninsula in Mexico
eon of oldest fossils
Archean Eon (3.2 Ga)
era of dinosaurs
Mesozoic Era
era that the badlands rocks were deposited?
Cenozoic era, Paleogene period
significance of banded iron formations in history of planet?
Indicates the oxygenation of atmosphere which causes the iron to settle out of the water and into banded formations in the ground (happened in Archean eon)
epoch of glaciations and name of most recent
glaciation
Pleistocene epoch (Quarternary period, Cenozoic era)
Wisconsin Glaciation, 21 ka
epoch since the ice ages
holocene (most recent epoch)
eon of oldest rocks in SD
Archean eon (millbank granite)
name of most recent glaciation
Wisconsin Glaciation, 21 ka
three aspects of mass movements that bear on their classification
material, velocity, type of movement
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
what effects might you see in an area where creep has been occurring?
cracked roads, cracked parking lots, tilted power poles, bent tree trunks, tilted vertical sedimentary beds
equation for force
force = mass x acceleration
with respect to forces associated with mass movements, under what conditions will mass movements occur?
increasing mass: add more geologic material, water, or construction
increasing acceleration: earthquakes
(decreasing resisting forces: steepen slopes, weaken slopes, decrease friction)
why does a modest amount of water actually increase the strength of sand?
Surface tension causes cohesion between water and grains
Under what condition does water allow unconsolidated material to flow?
liquefaction!
extreme saturation + shaking decreases friction between grains and weakens the material
What is solifluction?
slow flow of saturated soil (like creep but with a bit more flow)
happens due to ice deep within soil that thaws and expands/contracts, making lobes
Parts of a slump?
scarp/head scarp + slip surfaces + toe
ways in which human activities promote mass wasting and increase exposure to the hazard
we build right up to the edge of steep surfaces (both at bottom and at top) water mismanagement (farms) construction
what is the term for a volcanic mudflow/debris flow?
lahar
What is a stream?
water flowing downslope in a channel (rivers, creeks, &c)
Three geologic functions of a stream
Erosion
Transportation of sediment
Deposition of sediment
different ways that streams erode
scouring (eroding), plucking (breaking and lifting), abrasion (abrading bedrock)
Recognize in photos or diagrams the regional stream patterns and what simple geology causes them
dendritic (homogenous geology)
rectangular (jointed)
radial (volcano)
trellis (folded)
Be able to calculate discharge and gradient
Discharge: width x depth x velocity
Gradient: drop in elevation (top – bottom) /distance
Major watersheds (3) which are partly in SD (eg Missouri River)
Missouri River, Mississippi River, Minnesota/Red/Hudson?
Three types of load, how is material moved in each?
Bed load (rolling and saltation)
Suspended load (small particles stay off of bed)
dissolved load (transported as ions in solution)
What is the shape of a graded stream profile? straight, concave-up, or convex-up
Concave up
What is base level?
the elevation below which a stream cannot cut (sea level is ultimate base level)
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)
compare and contrast regional and flash floods
flash floods: in upper parts of basins, caused from intense downpour in small area but may not cause flooding in large rivers downstream, causes largest number of deaths
regional/seasonal floods: produced by storms of long duration or periods of sudden snowmelt, causes most damage
know the basics of the floods discusses in class (China 1931, Rapid City 1972, Vermillion 1881, Midwest 1993, Johnstown 1889 [reading])
China 1931: 3.7 million killed (worst nat disaster ever)
Rapid City 1972: 500 yr flood, 238 killed, 3,057 injured, $160 million in damage, Rapid Creek reached 50K cfs
Vermillion 1881: 3/4 of town destroyed, ice dam in yankton broke, town relocated to top of bluff
Midwest 1993: 50 killed, $15 billion in damage, happened between June and August, >190 days
Johnstown 1889: 2,300 dead, poorly made dam collapsed
How does development change flood behaviour?
examples of development: paving, building, destroying wetlands, reducing forest
effect: allows water to move more rapidly through system, duration of floods is shorter but the peak intensity is higher
Can a record of flooding be used to analyze floods of greater recurrence interval than the length of the record?
Yes (38 yr record can predict 100 yr flood)
What is the recurrence interval used by FEMA for floodplain mapping?
the average time between a flood and next occurrence of a flood of the same or greater magnitude
1/RI (x 100 for %)
The probability of having a 100 year flood in any given year is 1% (1/100 x100)
Determine probability of an RI-year flood in any given year (simple ones, so as to not require a calculator)
1/RI (x 100 for %)
The probability of having a 100 year flood in any given year is 1% (1/100 x100)
