Natural Disasters Exam 1 SG

define disaster

natural or man-made emergency whose response needs exceed the available resources of affected community

define hazard

a dangerous natural condition (earthquakes, floods, etc)

list three types of plate boundaries and their associated movements

divergent (new crust generates as plates pull away from each other)

convergent (crust is destroyed as one plate dives under another)

transform (crust is neither produced nor destroyed as plates slide horizontally past each other)

list three types of faults

normal fault (any fault where the rock above the fault falls downward)

reverse fault (any fault where the rock moves upwards)

strike-slip fault (any fault where two sides move horizontally past each other)

When studying natural disasters, how is “risk” defined and how do we measure it?

risk: product of extent, effects, probability, and importance of the outcome

measured by likelihood of negative impacts resulting from a natural hazard

define mitigation

activities to reduce loss from future disasters, like prevention and protection

list the 4 types of mitigation

alter the hazard (controlled avalanches), avert the hazard (dams, levees), adapt to the hazard (earthquake architecture), avoid the hazard (don’t develop hazard areas)

list the two examples of mitigation used

increasing emergency response capability (takes more to exceeds community’s needs), or start projects to prevent/lessen the impact of future incidents

Why do the Earth’s plates move and what types of hazards are direct results of plate tectonics?

plates move due to convection currents underneath plates

earthquakes

explain convection currents

rock at the bottom of Earth’s interior gets heated, rises to the surface, spreads, and begins to cool, then sinks to the bottom where it’s reheated and rises again

define hotspot

a location that’s particularly vulnerable to experiencing multiple or intense natural disasters

know the difference between continental drift and plate tectonics

continental drift explains the movement of continents only, while plate tectonics explains the movement of the whole plate

Who developed the plate tectonics theory, and what evidence did he use to support it?

Alfred Wegener → seafloor spreading, magnetic patterns in ocean crust, distribution of earthquakes and volcanoes, fossil and rock location correlations

What does the Moment magnitude scale measure?

measures energy released by an earthquake

What does the Mercalli scale measure?

measures observed effects and damage (is subjective)

What are some of the major effects of an earthquake after it subsides?

fire, liquefaction, tsunami, seiche (a wave in a lake caused by displacement of the lake bottom), landslides

What is a good example of a transform fault here in the US?

San Andreas fault

know the different layers of the Earth’s interior and if they’re solid or liquid

How do we know the state of the Earth’s layers?

crust (solid), asthenosphere (upper mantle - semisolid), lower mantle (liquid)

we know from seismic wave benavior

Which of the plate boundaries is usually associated with volcanoes and why?

convergent boundaries, specifically oceanic-continental → subducted oceanic crust melts and makes magma

How do the different seismic waves move and which type causes the most widespread damage to buildings?

p-waves: fastest, compressional, travel through solids and liquids

s-waves: slower, side-to-side, only through solids

surface waves: slowest, most destructive (Love and Rayleigh waves)

surface waves cause the most building damage

Review the case study table.

done

know the three largest earthquakes ever recorded

Chile, 1960

Alaska, 1964

Sumatra, 2004

know the difference between a focus and an epicenter

focus (hypocenter): the actual underground location where the quake begins

epicenter: the point directly above the focus on the earth’s surface → found by triangulating data from 3+ seismographs

define tsunami

a series of large ocean waves caused by underwater earthquakes, landslides, or volcanic eruptions

What do you do if an earthquake occurs?

indoors: drop, cover, and hold on under sturdy furniture, stay away from windows

outdoors: move to an open area away from buildings and power lines

Where do we generally find divergent and convergent plate boundaries?

divergent: mid-ocean ridges

convergent: subduction zones

What two major plates interact on the west coast of North America that form volcanic regions like the Cascades in Oregon and Washington?

Juan de Fuca plate and North American plate

What caused the formation of the Himalaya Mountains?

collision of the Indian plate with the Eurasian plate

know the primary plate motion, most common fault type, type of volcanic eruptions, landforms created, and what is commonly found at divergent boundaries

primary plate motion: pulling apart/moving away

most common fault types: normal faults

types of volcanic eruptions: typically effusive, not explosive (magma rises easily through the thinning crust)

landforms created: mid-ocean ridges, rift valleys, fissure volcanoes, new oceanic crust

commonly found: mid-ocean ridges, rift zones

know the primary plate motion, most common fault type, type of volcanic eruptions, landforms created, and what is commonly found at convergent boundaries

primary motion: plates move toward each other due to compressional forces

most common fault type: reverse/thrust faults

type of volcanic eruptions: explosive (plates melt and form magma, leading to violent eruptions)

landforms created: ocean trenches, volcanic mountain ranges, island arcs, fold mountains

commonly found: subduction zones

know the primary plate motion, most common fault type, type of volcanic eruptions, landforms created, and what is commonly found at transform plate boundaries

primary motion: horizontal (sliding past each other)

most common fault type: strike-slip fault

type of volcanic eruptions: none (no subduction to melt rock, no space created that allows magma to rise)

review the earthquake case study notes

done