geol 5 final
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What is the difference between ductile and brittle deformation?
- ductile: permanently deforming, bending
- brittle: breaking failure, snap
What factors determine how a rock will respond to stress?
- rate of strain
From a bird’s eye view, are older or younger rocks exposed in the core of an anticline? What about a syncline?
- Anticline - older in middle
- Syncline - younger in middle
Be able to draw a normal fault, a reverse fault, and a strike-slip fault, label the foot wall and hanging wall (for normal and reverse faults). Show the relative motion along the fault (i.e. hanging wall up or hanging wall down?).
Do normal faults occur under compression or tension? What about reverse faults? What about strike-slip faults?
- Normal: tensional
- Reverse: compressional
- Strike-Slip: shear
How do basins and domes form? Where are the oldest rocks in a basin? In a dome?
- Basin: bed dips inward, youngest in middle
- Dome: bed dips outward, oldest in middle
Describe the elastic rebound theory for how earthquakes are generated.
- Plastic strain builds up along fault
- Strain exceeds elastic limit
- Brittle failure
- Sides snap to new low-strain positions
What is the difference between the measures of earthquake magnitude and intensity
- Magnitude: measure of energy released in EQ, only 1 mag, Richter scale
- Intensity: measure of ground shaking in EQ, depends on distance & material, many intensities
What factors affect the intensity of shaking felt?
- Distance from epicenter
- Ground material
What is the difference between body waves and surface waves?
- body: move through earth, faster, P & S waves
- surface: move across surface, slower, more damage, Love & Rayleigh waves
What is the difference between P-waves and S-waves?
- P-Wave: primary, high velocity, compressional, back & forth, parallel to direction
- S-Wave: secondary, slower, transverse, side to side, perp to direction
Describe how you determine where the epicenter of an earthquake is.
- Triangulate using the distance and times from 3 stations
- Where all 3 circles overlap is the epicenter
How much bigger than a magnitude 3 earthquake is a magnitude 7?
The 1985 Mexico earthquake caused severe damage in some parts of Mexico City but not in others, why was this?
Different geological materials?
Explain how lithosphere and asthenosphere behave differently
- lithosphere: 100 km thick, rigid/brittle, floats on aesthenosphere
- Aesthenosphere: plastic/fluid
What is a tectonic plate?
Section of earth's crust
What are the three types of plate boundary?
Give one example of a transform plate boundary.
What are the three types of convergent margins?
- O-O - older & colder subducts
- O-C - oceanic subducts below cont
- C-C - no subduction, large mtn ranges
What is the significance of the trench found at subduction zones?
- Large EQs
- Very deep
What geologic hazards are associated with convergent plate margins?
- Large deep EQs
- Large mtn ranges
What types of plate boundary exist in Mexico?
Outline three different lines of evidence that was used to support continental drift
- Fit of continents
- Matching rocks
- Alignment of mountain ranges
Know what a hot spot is and an example of one
- Hot spot: plume of heat rising from mantle
- Hawaii, Yellowstone
What is an island arc and an example of one?
- Islands formed by tectonic process, convergent boundaries
Why wasn’t continental drift taken seriously when first proposed in the early 20th century?
No driving mechanism
What are two characteristics of mountain ranges?
- size & alignment: long and parallel to other ranges
- age: taller ranges tend to be younger
What is the relationship between how high a mountain range is and its relative age?
Taller = younger, not yet eroded
What is a craton?
- region of continent that has been structurally stable for prolonged period of time
- thin layer of sed rock
- same density rocks at mtn range
Be able to explain the term isostacy in terms of a mountain range.
- balance rock masses within earth
- heavier rocks sink
- lighter rocks float
- isostatic rebound
What is the atmosphere?
- envelope of gases surrounding the planet
- 78% nitrogen, 21% oxygen
What is the difference between weather and climate?
- weather: daily, given time and place, temp/precip/wind
- Climate: comp of weather patterns over long time, regional, seasons, years
What were the findings of the IPCC?
- Intergov Panel on Climate Change
- assessment of climate change
- human impact on climate
- emission of GHG highest in history
What do we know about temperature changes over the last century?
What are the probable consequences of climate change?
- sea level rise 23 inch by 2100
- 100M ppl live within 3 feet of sea level
- glaciers melt
- strong hurricanes, droughts, heat waves, fires
- deserts and food shortages
- mass extinction
- ocean conveyor belt altered
- positive feedback effect
When air sinks and heats up which is more likely, evaporation or precipitation?
How much have global climate temperatures increased over the past 100 years?
What causes waves to form?
strong winds blowing across the ocean
What is the difference between a summer beach and a winter beach?
- Summer: gentle waves, wide beach
- Winter: storm waves, small beach
What is longshore drift and how does it affect the coastline?
- Sand being transported along the beach
- Moves sand by striking at angle
- causes erosion and deposition
What are groins, jetties and breakwaters and how do they disrupt longshore drift?
- groin: object sticking out from beach, blocks sand from moving, causes dep & erosion
- jetties: extensions from land to prevent waterways from being blocked by deposition
- breakwater: object offshore to break waves early
What is wave refraction and how does that relate to coastal straightening?
- slowing & bending of waves in shallow water
- one side hits first, starts to bend
- wraps around headlands to hit on both sides
What man-made measure are used to combat coastal erosion?
Describe two landforms found along an erosional coastline.
- marine terrace - bedrock lifting up
Describe two landforms found along a depositional coastline.
- barrier island
- tombolo - sand bar connecting land & island
- lagoon - isolated by barrier island
Know the difference between an emergent coastline and a submergent coastline
- emergent: drop in sea level relevant to sea level fall or tectonic uplift, marine terrace
- submergent: rise in sea level relevant to sea level rise or tectonic downthrow, estuaries
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