ESCI 111 Exam 3 flashcards |

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What is the Law of Superposition? Why is it important?

the youngest layer is at the top, and the oldest layer is at the bottom
relative age may be determind

What is the Principle of Horizontality? Why is it important?

Layers are parallel to the Earth's surface

What are unconformities, angular unconformities, nonconformities, and disconformities?

1. unconformities- sequence of rock contains gaps, record change in environment that affect deposition
angular
2. angular unconformities- underlying layers are not parallel to the strata above it

Compare the meanings of relative (comparative) age/dating and absolute (numerical) age/dating with examples from geology ~ SHORT ANSWER

absolute aging- determining absolute time is important to understanding the rate of geologic processes ex) determining age of the earth

Why is the discovery of radioactive decay important in geology (two reasons)?

atoms may change into another element
half lives

What is radiometric dating? What is it based on? Why is it important?

determination of parent and daughter isotopes may be used to calculate age.

What does "half-life" mean?

The rate of change of radioactive nuclei

The time required for one half of the original mass of an isotope to undergo radioactive decay

What are some other methods of getting absolute ages (dates)?

Tree rings (ring thickness gives info on climate and time), Varves (rhythmic changes in sedimentary environment), Ice layers (thin layers of ice formed by annual snow fall)

According to geologists, about how old is the Earth? What is this estimate based on? Explain how geologists estimate the age of the Earth. ~ SHORT ANSWER

4.3 billion years old. Age was measured by the oldest rocks and crystals on the earth.

What is deformation? What causes rocks to deform?

Deformation - the changes in shape or position of a rock body in response to differential stress.

What are the two types of stress?

compressional and tensional

What are the three types of differential stress?

compressional, tensional, and shear

What happens to rock under stress in the upper and lower parts of the crust? ~ SHORT ANSWER

upper crust- brittle deformation (stress exceeds the strength of rock causing it to break)
lower crust- ductile deformation (creates folds where rock bends without breaking)

What are anticlines and synclines? What kind of rock do they form in?

anticline- form by up-folding or arching of sedimentary layers
syncline- troughs often found in association with anticline
-They both form in sedimentary rock

What is a fault? What is a joint? How are they different?

Fault - form where brittle deformation leads to fracturing and displacement of the Earth's crust
Joint - Fractures along which no appreciable displacement has occured

What are strike-slip faults?

Fault with dominant displacement horizontal and parallel to the direction of the fault

Define earthquake, earthquake focus (hypocenter), and epicenter

1. Earthquake- the vibration of Earth produced by the rapid release of energy
2. Earthquake focus- released energy radiating in all directions (the source)
3. epicenter

How do earthquakes occur? Who discovered the mechanism that explains the causes of earthquakes? What is the process? ~ SHORT ANSWER

elastic rebound- rocks on both sides of fault are deformed and bend which stores elastic energy causing frictional resistance. Slippage then occurs causing the deformed rock to spring back to its original shape
discovered by HF Reid

What are foreshocks and aftershocks?

1. Foreshocks- small earthquakes that follow major earthquakes
2. Aftershocks- adjustments that follow a major earthquake

What is seismology? What is a seismograph?

1. Seismology- study of earthquakes
2. seismograph- an instrument that measures and records details of earthquakes, such as force and duration.

Define and compare P waves and S waves.

p waves- primary waves, push pull, travels fast and through everything
s waves- secondary waves, shake motion, travels only through solids

Define and compare intensity and magnitude

1. Intensity - a measure of the degree of earthquake shaking at a given locale based on the amount of damage
2. Magnitude - estimates the amount of energy released at the source of the earthquake

What is the Richter scale? What does it measure? What is it used for?

scale based on the amplitude of the largest seismic wave.
accounts for the decrease in wave amplitude with increased distance

What is moment magnitude?

size of the earthquake based on energy released

What is the San Andreas Fault system? What is happening there?

system composed of numerous faults, extending 2000 miles.

What four factors determine the amount of structural damage from an earthquake? (p. 378)

1. intensity
2. duration of vibrations
3. Nature of material upon which the structure rests
4. design of structure

What is liquefaction?

unconsolidated materials saturated with water turn into a mobile fluid

What is a tsunami? What was the Tsunami of 2004? What happened? What caused it?

destructive waves

Where do most of the earthquakes in the world occur?

along the edges of the continental and oceanic plates

Can earthquakes be predicted in the short-term?

yes

What types of plate boundaries usually are associated with earthquakes? Explain each of the main types (i.e. convergent, transform, divergent) with examples ~ SHORT ANSWER

1. convergent- two plates come together ex:
2. divergent- areas where molten materials rise usually along extensive underwater mountain chains known as ridges and rises. The rising material results in the production of crustal material. Shallow earthquakes occur along these boundaries.
3. transform- occur where plates slide past one another. The classic example of this type of boundary is the San Andreas Fault

Describe what happened in Japan on March 11, 2011. Be familiar with the "Japan's Killer Quake" ~ SHORT ANSWER

Magnitude 9 earthquake hit Japan, causing a tsunami. Ruptured along a fault zone off the coast

What is mass wasting? (Definition - main characteristics) What are the factors that trigger mass wasting? ~ SHORT ANSWER

Mass wasting- downslope movement of rock, regolith, and soil under the influence of gravity
1. some triggers are saturation of material with water, oversteepening of slopes, removal of vegetation, and ground vibrations

What effects does water have on mass wasting? (Three things)

1. can trigger mass wasting
2. saturation reduces internal resistance of materials
3. adds weight

How can human activity sometimes lead to mass wasting events?

1. creating oversteepened and unstable slopes
2. forest fires and vegetation removal

What is angle of repose?

the steepest angle at which a sloping surface formed of a particular loose material is stable.

By what three factors are mass wasting processes classified?

1. type of material involved
2. the kind of motion displayed
3. rate of movement

What is a slump? Where does it usually occur and what causes it?

sliding of a mass of rock or unconsolidated material as a unit along a curved surface. commonly occur because slope has oversteepened and doesnt move very far.

What is a rockslide? Where does it usually occur and what causes it?

blocks of bedrock break loose and slide down a slope. Fast and destructive, occur where the rock strata are inclined

What is a debris flow? Where does it usually occur and what causes it?

flow of soil and regolith containing a large amount of water. Often confined to channels and canyons and also semiarid regions

What is an earthflow? Where does it usually occur and what causes it?

form on hillsides in humid regions during times of heavy precipitation.

What is creep? Where does it usually occur and what causes it?

gradual downhill movement of soil and regolith.

12. What is solifluction? Where does it usually occur and what causes it?

special type of creep that occurs in areas of permafrost. caused when water cannot escape from surface layer

1. What is glacier and how does it form? What are the two main zones on a glacier? What happens in each zone? (pp. 599-600) ~ SHORT ANSWER

natural body of ice formed by accumulation, compaction, and recrystalization of snow that is thick enough to flow and persists from year to year

What are the two main types of glaciers? Describe their main characteristics. Where do we find them, for example?

ice sheets and alpine or valley glaciers

5. How do glaciers erode the landscape? What is plucking and what is abrasion?

plucking and abrasion
plucking- loosening and lifting of rock blocks
abrasion- rocks within the ice acting like sandpaper to smooth and polish the surface below

6. Be familiar with the glacial landforms discussed on pp. 607-617.

Glaciated valleys, aretes and horns, roches moutonnees, fiords, tarns, cirques, hanging valleys

With regard to continental glaciers, what are drift and till

drift- all sediments of glacial origin
till- material that is deposited as glacial ice melts and drops its load of rock fragments

What are end and ground moraines?

end- ridge of till that forms at the terminus of a glacier
ground-gently rolling layer of till deposited as the ice front recedes

11. What were the eight major effects of the Pleistocene Ice Age? Know what they all are for possible multiple-choice questions and be able to explain three of them (a few sentences or phrases) for one of the short essays.

1. Sea level change- ice trapped huge quantities of water, topography of continental shelves are evidence
2. Pluvial lakes- rain fed lakes developed in arid and semiarid regions
3. Ocean waters cooled- changes in ocean chemistry and altered ocean circulation

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