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GEOL 1301 Natural Hazards and Disasters - Exam 1 Review
Chapters 1 - 5
Terms in this set (61)
What are Earth's internal and external processes? What is the energy that drives them?
Internal forces deep within Earth & Earth's internal energy; Result of plate tectonics - volcanoes, earthquakes.
External forces acting on Earth's surface; Energy from the Sun (storms, flooding, coastal erosion) and gravity (landslides).
What is the difference between natural hazards and natural disasters?
A natural hazard is a process and event that is a potential threat to human life and property due to human use of land. They are also repetitive events. Ex: landslides, earthquakes, flooding, tsunami, etc.
A natural disaster is a hazardous event which occurs over a limited time span in a defined area.
What criteria must be met in order for something to be classified as a disaster?
At least ONE of the following:
10 or more people killed
100 or more people affected
State of emergency declared
International assistance requested
What is the difference between a catastrophe and a disaster?
A catastrophe is a massive disaster that requires large amounts of money and a long time (often years) to recover from. Whereas a disaster has criteria related to deaths and injuries to people. Ex: Hurricane Katrina
Why are catastrophes increasing?
Impact has been affected by human population density and land-use patterns. The number of natural disasters has increased dramatically over the last 50 years. Increased population leads to people settling in unsafe areas.
What is mitigation?
To try to reduce or lessen the effects of something.
What is the difference between anticipatory and reactive responses?
Reactive - occurs after the disaster. Includes providing emergency services (search and rescue, food, water, shelter).
Anticipatory - work done prior to hazardous event. Includes land-use planning, hazard resistant construction, hazard modification and control.
What is the impact of global warming on natural hazards?
Sea level rise will lead to increased coastal erosion. Deserts and semi-arid areas will increase leading to more drought; will cause shift in food production areas as well as population shifts. Warmer ocean water will likely lead to more frequent and larger storms.
What are natural service functions of natural hazards?
Important benefits are provided by some natural hazards.
EX 1. periodic flooding supplies nutrients to floodplains creating fertile soils for farming.
EX 2. Volcanoes create new land; volcanic ash increases nutrients in soil.
EX 3. Earthquakes create fault gouge which can allow groundwater or hydrocarbons to collect.
What is the frequency/magnitude relationship of natural hazards?
Magnitude of event - amount of energy released.
Frequency of event - interval between occurrences.
Frequency is generally inversely related to magnitude.
What is the difference between forecasts and predictions?
Predictions of hazardous events specify the date, time and size of the event; can be used for floods, hurricanes, tsunamis, tornadoes; get out of harms way.
Forecast has ranges of certainty; allows for preparation.
How is risk calculated?
(Probability of event) x (Consequences)
Consequences = damages to people, property, economics, etc.
What factors influence the impact of natural hazards?
Climate system involves interactions between the atmosphere, hydrosphere, cryosphere, lithosphere, and the biosphere.
Plate tectonic system includes interactions between the lithosphere, asthenosphere, and deep mantle.
What cycles are included in the geologic cycle?
What is included in the tectonic cycle?
Involves the creation, movement, and destruction of tectonic plates.
Is responsible for:
Production and distribution of rock and mineral resources
Distribution of hazards such as earthquakes and volcanoes
What are the 3 main rock groups and how do each of them form?
Igneous rocks: form from crystallization of molten rock.
Sedimentary rocks: form when rocks are weathered into sediment by wind and water.
Metamorphic rocks: form when rocks get changed by extreme heat, pressure or chemically active fluids.
What does the internal structure of the earth consist of and what are the major characteristics of each layer?
Inner core: Solid; High temperature, Composed primarily of iron and other elements (sulfur, oxygen, and nickel).
Outer core: Liquid; Composition similar to inner core
Mantle: Solid; Composed of iron and magnesium-rich silicate rocks.
Crust: Outer rock layer of Earth; Moho discontinuity at the base of the crust (separates lighter crystal rocks from more dense mantle).
Lithosphere vs. Asthenosphere
Lithosphere - cool, strong, rigid outermost layer of Earth.
Asthenosphere - hot, slowly flowing layer of weak rock within the mantle (located at the base of the lithosphere).
What are the characteristics of the different types of plate boundaries and the types of processes occurring at each?
Divergent: plates moving apart and new lithosphere produced in mid-oceanic ridge
Convergent: plates collide, subduction and mountain building
Transform: two plates slide past one another
What are Wadati-Benioff zones and where do they occur?
dipping planes of earthquakes found near subduction zones. Plane indicates path of descending plate
What is the development and location of hot spots?
Volcanic centers resulting from hot materials from deep in the mantle. Can be used to determine rate and direction of plate movement. Materials move up through mantle and overlying plates. Found under both oceanic and continental crust. Plates move over hot spots creating a chain of island volcanoes.
What are the two possible driving mechanisms for moving plate tectonics?
Ridge push: a gravitational push away from crest of mid-ocean ridges.
Slab pull: occurs when cool, dense ocean plates sink into the hotter, less dense asthenosphere.
Evidence suggests that slab pull is the more important process.
What technology is used to explore the earth's interior?
Knowledge of the Earth's interior is based on the reactions of seismic waves from earthquakes to the density and state of materials that they encounter.
Development of plate tectonic theory?
Alfred Wegener presented the first detailed accounts of how today's continents were once a large supercontinent that slowly drifted to their present positions.
Where is the general location for earthquakes?
The majority of large and destructive earthquakes occur along transform boundaries where the plates meet, like the San Andreas Fault Zone.
What is the importance of finding magnetic reversals on the sea floor?
Using the magnetic anomalies, geologists can infer ages for the ocean rocks. Seafloor spreading at the mid-ocean ridges can explain stripe patterns.
What are the hazards expected at different plate boundaries?
Divergent plate boundaries that slide past each other (Mid-Atlantic Ridge) exhibit earthquakes and volcanic eruptions.
Convergent plate boundaries where one plate sinks beneath another (subduction zones) are home to explosive volcanoes and the greatest earthquake hazards.
What is the focus and epicenter of earthquake?
Epicenter: point on surface above the focus.
Focus: point on fault where rupture began; in subsurface.
How is the magnitude of an earthquake measured?
Using the 'Moment Magnitude Scale'. Determined from area of rupture on fault, amount of slippage along the fault, and the rigidity of the rocks near focus.
How is the intensity of an earthquake measured?
Modified Mercalli Scale: based on damage to structures and people's perceptions. Maps show where the damage is most severe.
What are the different fault types and hanging wall/ footwall relationships.
*Strike-Slip: Fault blocks slide past each other in horizontal direction. Caused by shearing of the crust.
*Dip-Slip I: Vertical movement of fault blocks. Include two walls defined by miners as: footwall where miners put their feet and hanging-wall where they put their lanterns.
*Dip-Slip II: Normal fault - Hanging wall moves down relative to footwall. Caused by crustal extension.
*Reverse fault: Hanging wall moves up relative to footwall. Caused by crustal compression.
*Blind faults: do not extend to the surface.
What are the characteristics of P and S waves?
P waves: primary or compressional waves. Move fast with a push/pull motion. Can move through solid, liquid and gas.
S waves: secondary or shear waves. Move slower with an up/down motion. Can travel only through solids
What is the difference in arrival times for P and S waves on seismographs?
Distance from earthquake / (S-wave speed) - distance from earthquake / (P-wave speed).
What factors influence the intensity of shaking caused by an earthquake?
Earthquake magnitude, Location in relation to epicenter and direction of rupture; depth to focus.
Supershear may result in more intense shaking. Local soil and rock conditions.
What is triangulation?
At least three stations are needed to find exact epicenter. Distances from epicenter to each station are used to draw circles representing possible locations. The place where all three circles intersect is the epicenter.
What is material amplification?
As P and S waves slow down, forward energy is transferred to the vertical motion of the surface waves.
Where do the largest earthquakes occur?
What is liquefaction?
A near-surface layer of water-saturated sand changes rapidly from a solid to a liquid. Causes buildings to "float" in earth; fall over. After shaking stops, ground re-compacts and becomes solid.
What threats are caused by earthquakes?
Loss of sanitation and housing, contaminated water supplies, disruption of public health services and disturbance of the natural environment.
What forms of human impact can cause earthquakes to occur?
Loading Earth's crust, as in building a dam and reservoir. The weight from water reservoirs may create new faults or lubricate old ones.
Injecting liquid waste deep into the ground through disposal wells. Causes increase in fluid pressure along fractures or faults allowing them to slip.
Creating underground nuclear explosions. Nuclear explosions can cause the release of stress along existing faults.
What predictions can you make prior to earthquakes occurring?
Pattern and frequency of earthquakes, Deformation of ground surface, Changes in land elevation, Seismic gaps along faults, Changes in Earth's magnetic field, groundwater levels, electrical conductivity.
How many earthquakes are estimated each year?
More than 3 million per year.
What causes are Tsunamis triggered by?
Caused by a sudden vertical displacement of ocean water. Large earthquakes that cause uplift or subsidence of sea floor; these are the most common.
Other causes: Asteroids, Submarine volcanic explosion, Underwater landslides.
What are the characteristics of a Tsunami?
Need > M 7.5 earthquake to create enough displacement. Rupture uplifts the seafloor. A dome forms on the surface of the water above the fault. Dome collapses and generates the tsunami wave. Waves radiate outward.
Travels out across the deep ocean at high speed for thousands of kilometers to strike remote shorelines with very little loss of energy.
Heads in the opposite direction toward the nearby land and arrives quickly following an earthquake.
Why are shorelines at risk for Tsunamis?
Coasts close to a major subduction zone or directly across the ocean basin from a major subduction zone are at greatest risk.
The Cascadia subduction zone, the Chilean trench, the subduction zones off the coast of Japan, and parts of the Mediterranean.
What are ways to minimize the Tsunami hazard?
Detection and warning
Construction of tsunami runup maps
Land use planning
What are the 3 components for a Tsunami warning system?
A network of seismographs to measure submarine movements.
Automated tidal gauges to measure unusual rises and falls of sea level.
Buoy sensors with tsunameter to detect small changes in pressure in ocean as tsunami passes overhead.
How can you detect a Tsunami?
Distant tsunamis can be detected in the open ocean and can accurately estimate their arrival time to within a few minutes.
What are Tsunami runup maps?
Shows the level to which the water traveled inland or is projected to travel inland. Before a tsunami strikes, a community can produce a hazard map that shows the area that is likely to be inundated by a given height.
What is a Tsunami watch?
An earthquake that can cause a tsunami has occurred.
What is a Tsunami warning?
A tsunami has been detected and is spreading across the ocean toward their area. Tsunamis come in a series of waves - the second and third waves may be larger than the first one.
What is the difference between magma and lava?
Magma is molten rock below Earth's surface.
Lava is magma erupted onto the Earth's surface.
What are Calderas and how do they form?
A caldera is a volcanic feature formed by the collapse of land following a volcanic eruption. Very large craters formed from violent collapse of a cone and contain vents and hot springs.
What are the threat levels of various types of volcanic hazards?
Primary Effects: lava flows, ash fall, pyroclastic flows and release of volcanic gases.
Secondary Effects: debris flows, mudflows, landslides or debris avalanches, floods, fires, and both global cooling and global warming.
What causes the 'Ring of Fire'?
A direct result of plate tectonics and the movement and collisions of lithospheric plates. The Ring of Fire is an area in the Pacific ocean where a numerous number of earthquakes and volcanic eruptions occur. About 80% of the world's largest earthquakes happen along the Ring of Fire.
What are the precursors before a volcano erupts?
Before a volcano erupts, magma must force its way upward through solid rock beneath a restless volcano. This process causes the ground above to heave and shake as rock is shoved aside or broken. At the same time, gases are released from the magma as it rises to shallower levels where the pressure is lower and the temperature of the ground increases.
What are the 3 types of magma based on silica content?
Low to high: Basaltic, andesitic, and rhyolitic
How does silica content affect the viscosity of magma?
Viscosity affects the flow of lava and therefore the shape of resulting volcano as well as its eruption style. High silica content, high viscosity (harder to flow).
What type of magma exhibit highly explosive eruptions?
The highly viscous (rhyolitic) magma.
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