Geology Final Exam: Review Questions

Front 1

What is the difference between the focus and the epicenter of an earthquake?

Back 1

Epicenter is the point on the Earth's surface directly above the focus. The focus is the actual location of the earthquake (fault rupture) below the Earth's surface. It is the point from which seismic waves originate.

Front 2

How is Richter magnitude determined?

Back 2

It is the measure of how much total energy was released. Measured using a seismograph (machine). The piece of paper with the data is called the seismogram.

Front 3

What factors determine the modified Mercalli Scale?

Back 3

Measures the intensity of the earthquake based on how concentrated the energy is. Scientists get their values, in Roman numerals, from what people saw/felt using surveys.

Front 4

What are the major types of faults?

Back 4

Normal Faults: Vertical movement, footwall goes up, tension, causes lengthening.
Reverse Fault: Vertical movement, footwall goes down, compression, causes shortening.
Strike Slip Faults: Horizontal movement, shear, causes tearing and smearing, right/left lateral.

Front 5

What is the difference between an anticline and syncline?

Back 5

Anticlines are arch-shaped folds; synclines are bowl shaped folds. Anticlines form ridges and synclines form basins at the surface of the ground.

Front 6

How do we define an active fault?

Back 6

Considered active if it can be deomanstrated to have moved during the past 10,000 years.

Front 7

What are the main types of seismic waves (Shaking)?

Back 7

Body Waves- seismic waves that pass through the Earth's interior in all directions. (like sound waves through water or air).
Surface Waves- stuck on Earth's surface, slowest, most damage, seismic waves that move only along the surface of the Earth. (Like ripples on the surface of water)

Front 8

Describe the motion of P, S, and R waves. (Body Waves)

Back 8

P Waves (Primary): Compressional waves, fastest waves, 1st to arrive at seismic station. Particle move parallel to direction of wave travel. Move through solid, liquid or gas.
S Wave (secondary) (sheer) - shear waves, slower than p waves, second to arrive at seismic station, particles move perpendicular to direction of wave travel, move only through solids.
R Waves - rolling up and down motion, slowest waves, last to arrive at seismic station, most destructive, a form of surface waves.

Front 9

Define the earthquake cycle, and illustrate it with a simple example.

Back 9

Four stages:
Period of seismic inactivity-during which elastic strain builds up in the rocks along a fault.
Followed by a period of increased seismicity as the strain locally exceeds the strength of the rocks, initiating local faulting and small earthquakes.
Third stage consists of foreshocks, but doesn't always occur.
Fourth stage is the major earthquake, which occurs when the fault segment ruptures, producing the elastic rebound that generates seismic waves.

Front 10

How has human activity caused earthquakes?

Back 10

Increased it by loading Earth's crust through construction of large reservoirs; by disposal of liquid waste in deep disposal wells, which raises fluid pressure in rocks and causes movement along fractures; and by setting off underground nuclear explosions.

Front 11

What are somee of the major effects of earthquakes?

Back 11

They include violent ground motion accompanied by fracturing, which may shear or collapse large building, bridges, dams, tunnels, and other structures. Other effects include liquefaction, landslides, fires, and tsunamis.

Front 12

What are some of the precursory phenomena likely to assist us in predicting earthquakes?

Back 12

Based on previous patterns and frequency of earthquakes as well as by monitoring the deformaation of land, the release of radon gas, and existing seismic gaps. A potential problem of predicting earthquakes is that their pattern of occurence isoften variable, with clusterring of events seperated by longer periods of time with reduced activity.

Front 13

What are the major goals of earthquake hazard reduction programs?

Back 13

Includes recognition of active faults and Earth materials sessitive to shaking and development of improved ways to predict, control, and adjust to earthquakes, including designing features to withstand them better. Education of public.

Front 14

What are the main diffeerences between the Richter, Moment Magnitude, Modified Mercalli and Instrumental scales?

Back 14

Modified Mercalli - the measure of the intensity of an earthquake, based on the severity of shaking as reported by observers and varies with proximity to the epicenter.
Richter - shake maps based on a dense network of seismographs can quickly show areas where potentially damaging shaking occurs.

Front 15

What is viscosity, and what determines it?

Back 15

Viscosity is the runniness of lava.
Low viscosity- thin and runny
High Viscosity- thick and pasty, doesn't flow far.
Viscosity is influenes by the temperature and composition.

Front 16

List the major types of volcano and the types of magma associated with each.List the major types of volcano and their eruption style. Why do they erupt the way they do?

Back 16

Activity of volcanoes due to silica content and viscosity.
Shapes of volcanoes are due to different viscosities.
Shield- Common rock type is basalt an characteerized by nonexplosive lava flows. base is spread, low viscosity, ex are the Hawaiin Islands, they don't get massive explosions.
Composit or Strato- composed of andesite rock and characterised by explosive eruptions and lava flows.steep side, high viscosity, explode, falsic lava, ex are the Cascades such as Mt. St. Helens. Basaltic lava- dark, low viscosity, very runny.
Cinder cone - vent where lava comes out and solidifies in air.
Caldera - completly exploded, left with whole in ground.
Domes - composed of rhyolite rock and highly explosive.

Front 17

Differenciate between ash falls, lateral blasts, and ash flows.

Back 17

Pyroclastic hazards include volcanic ash falls, which may cover large areas with carpets of ash; ash flows, or hot avalanches which move fast down the side of a volcano, and lateral blasts which can be very destructive.

Front 18

What is the relationship between plate tectonics and volcanoes?

Back 18

Directly, most volcanoes are located at plate boundaries, where magma is produced as spreading or sinking plates intereract with other Earth material.

Front 19

How do lava tubes help move magma far from the erupting vents?

Back 19

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Front 20

What is the relationship between the Hawaiin Islands and the hot spot below the big island of Hawaii?

Back 20

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Front 21

Why are caldera eruptions so dangerous?

Back 21

They are violent, but rare, present a danger for millions of years.

Front 22

List the primary and secondary effects of volcanic eruptions.

Back 22

Primary effects include lava flows, pyroclastic hazards, and emission of poisonous gasses such as H2o, Carbon monoxide which is dangerous b/c it is heavier than surrounding air and kills, and sulfur. seconday effects include debris flows and mudflows.

Front 23

What are some of the methos that have been attempted to control lava flows?

Back 23

Hydraulic chilling and the construction of walls have been used in attempts to control lava flows.

Front 24

How are volcanic eruptions able to produce gigantic mmudflows?

Back 24

Mudflows are generated when melting snow and ice or percipitation mixes with volcanic ash. Devastating

Front 25

What are some of the possible methods of forecasting volcanic eruptions?

Back 25

Monitoring of seismic activity, thermla, magnetic, and hydrologic properties, and topographic changes, with ocmbined knowlege of the recent geolgic history of volcanoes results in forecasting of activity. Forecasting has generally been acurate in Hawaii and the Phillipeans.

Front 26

What are the main ways that materials on a slope may fail?

Back 26

Classify: Material and motion
Material- rock, earth, debri
Motion (movement) slide (plane)transitional: along a plane or slide vs. rotational: curved escarpment or slump,fall(air)materials freefall or tumble down a slope, slump (curved failure surface), flow: when material mixes and moves in a fluid like nature, not as a unit. (wet, difficult to have a rock flow)
Creep: very slow movement of material.

Front 27

What is the safety factor, and how is it defined?

Back 27

Is the ratio of resisting forces to driving forces; a ratio greater than one means that the slope is stable; a ratio less than 1 indicates potential slope failure.

Front 28

Differenciate between rotational slide (slumps) and translational slides and shallow slips.

Back 28

Transitional slides occur along a plane.
Rotational occur on a curved escarpment or they slump.

Front 29

How does the slope angle affect the incidence of landslides?

Back 29

Gravity is the driving force; friction, strength, and toe are resistance. Increase the drive, or decrease resistance you get mass wasting.

Front 30

Why does time play an important rolse in landslides?

Back 30

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Front 31

What is the main lesson learned from the Vaiont Dam disaster?

Back 31

The side of a mountain slipped into a lake. Scientists saw cracks and signs. It created a lake tsunami which broke the damn and killed 3000. The lesson learned was to pay attention to cracks and ask why signs are happening.

Front 32

How might the pprocess of urbanization increase or decrease the stability of slopes?

Back 32

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Front 33

What are the main step we can take to prevent landslides?

Back 33

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