Natural Disasters Test 1 Study Guide

Mohorovic discontinuity-

-named after seismologist Anrija Mohorovicic -1909 discovery of a density boundary between the crust and mantle lithosphere -based on differences in the velocities of seismic waves

Climate related disasters:

-severe weather (e.g. cyclonic storms) -blizzard -flood -drought -heat waves -tornadoes

Plate Techtonics:

Earth's outermost layer (i.e. the lithosphere) is broken down into 15 rigid plates that move laterally across the surface

Seismic waves are generated by the _______________.

Instantaneous disturbance or rock

The East African rift is a divergent plate boundary that is splitting the continent of Africa into two pieces. What will eventually form around this divergent boundary? -a continental hurricane -a convergent boundary -an ocean transform boundary

an ocean

Fault (divergent plate boundary)-

brittle fracture of rock along with motion

Athenosphere is the ________ layer.

weak

When do new oceans form? -when a continent is broken apart by an ocean boundary -when a continent is broken apart by a divergent boundary -when a continent is broken apart by a convergent boundary -when an ocean is broken apart by a divergent boundary -when an ocean is broken apart by a convergent boundary

when a continent is broken apart by a divergent boundary

Subduction-related volcanic arc-

-A parallel volcanic chain or arc forms 100-300km from the subduction trench -Water contained in the subjecting plate is released at 100km depth (aka slab dehydration) -The released water lowers the temperature of the rocks. The rocks turn into magma. Etc.

Where are most modern divergent plate boundaries found? At transform boundaries -At mid-ocean ridges -At continental margins -Within continents -At subduction zones

-At mid-ocean ridges

____________ natural disasters are generated by human activity.

Anthropogenic

____________ occurs at all three types of plate boundaries.

Seismicity (i.e. earthquakes)

Faults capable of generating earthquakes are called ________.

Seismogenic

How fast do slow plates move?

Slow plates move at the rate of fingernail growth -> 30 mm/yr (e.g. Indian plate)

Disasters induced by climate & geological processes can be related (t or f)

True, they can be related. (i.e. Indian Asia collision resulting in uplift of Himalaya plateau and monsoon rains and flooding across the Indian subcontinent

What is a natural disaster?

- physical event attributed to geologic and or/ atmospheric processes that could be detrimental to humans. -Could have natural and/or anthropogenic influences

Subduction Zones (>40 degree dip angle (convergent)-

- An oceanic plate converges with either a continental or oceanic plate -The denser plate is forced under

Oceanic crust-

-Basaltic in composition -10km thick - p=3.0 g/cm3

Disasters induced by geologic processes:

-earthquakes -tsunami -landslides -volcanism -sinkholes -liquefaction

We must study natural disasters to understand:

-future potential HAZARDS -mitigate potential RISK -Dynamic nature of earth processes

Friction keeps the fault from continuing to slip. This is called _________ behavior.

stick-slip

Oceanic versus continental crust

-earth's crust is either continental or oceanic in composition -Oceanic: Basaltic in composition -Continental: Granitic in composition

Which of the following hazards would you expect to see at a divergent plate boundary? Large earthquakes; no volcanoes; landslides and flooding due to the large plateau of very high mountains Moderate strength earthquakes; non-explosive volcanic eruptions; flooding if volcanoes erupt underwater such as in Iceland Large earthquakes; explosive volcanic eruptions; landslides and flooding due to long chain of volcanic mountains large earthquakes; no volcanoes; flooding if the plate boundary is hilly

moderate strength earthquakes; non-explosive volcanic eruptions; flooding if volcanoes erupt underwater such as in Iceland

Earthquake-

movement of the Earth's surface caused by seismic waves, which travel through earth.

After the lithosphere has been sufficiently extended, ____________ is generated along the rift axis. At this stage, the rift is a ___________ plate boundary.

new lithosphere; divergent

Earth's outermost layers (i.e. crust, upper and lower mantle) are typically distinguished by:

-Chemical composition (i.e. density) -Rhetorical strength (i.e. viscosity)

Plate techtonics explains:

-Development of mountains, valleys, and basins -Distribution and timing of earthquakes, volcanism, and some landslides

Volcanism occurs at __________.

-Divergent boundaries (i.e. rift zones) -Convergent boundaries (typically subduction zones)

What generates seismic waves?

-Explosion -Meteorite impact -Landslide -Magma flow -trains, cars, etc. -People walking -Sudden slip or rupture along an active fault

Continental crust-

-Granitic in composition -30km thick - p=2.7 g/cm3

Hazard vs. Risk

-Hazard has potential to harm humans. -Risk is the chance that harm to humans will occur due to that hazard.

Which of the following hazards would you expect to see at a convergent plate boundary associated with a subduction zone? -Large earthquakes; no volcanoes; landslides and flooding due to the large plateau of very high mountains -Moderate strength earthquakes; non-explosive volcanic eruptions; flooding if volcanoes erupt underwater such as in Iceland -Large earthquakes; explosive volcanic eruptions; landslides and flooding due to long chain of volcanic mountains -Large earthquakes; no volcanoes; flooding if the plate boundary is hilly

-Large earthquakes; explosive volcanic eruptions; landslides and flooding due to long chain of volcanic mountains

What causes plates to move?

-Mantle heat flow (i.e. convection) -Ridge pull -Slab pull

Divergent plate boundaries (characteristics):

-Plates move away from each other along a linear rift zone -Typically develop above zones of mantle upwelling -Divergent boundaries are also called spreading centers -Divergent boundaries are associated with LOTS of volcanism and the generation of new lithosphere -Examples: Mid-atlantic ridge, Red Sea, east pacific rise, east African-afar rift

Transform Plate Boundaries-

-Plates slide past each other horizontally between a vertical fault -Also called strike-slip plate boundaries or faults

Development of a Divergent Plate Boundary:

-Rifting is the surface expression of extensional deformation -Extensional deformation= solid stretching of a material from an undeformed state -Extensional deformation (i.e. rifting) of the lithosphere is accommodated by two processes (1. normal faulting in the crust 2. Ductile thinning of the mantle lithosphere)

East African- Afar rift zone:

-Series of north-south-trending, active rift zones across E. Africa -Extend south from the Red Sea divergent plate boundary -EXTREMELY volcanically active (e.g. Mt. Nyiragongo, DRC)

Continental-Continental collisions-

-The best active example is the India-Asia collision zone, which generated the Himalaya mountains and Tibetan Plateau -India is being underthrusted beneath Asia.

What is the difference between the inner and outer core of the Earth? -The inner core is made from magma and the outer core is metal. -The inner core is cool and the outer core is hot.The inner core is solid and the outer core is liquid. -The inner core is liquid and the outer core is solid. -The inner core is hot and the outer core is cool.

-The inner core is solid and the outer core is liquid

Oceanic-Continental Subduction zone (convergent)-

-The more dense oceanic plate subjects beneath the less dense continental plate -The subjecting plate extends deep into the mantle

Oceanic-Oceanic Subduction zone (convergent)-

-The more dense oceanic plate subjects beneath the less dense continental plate.- -The subducting plate extends deep into the mantle

Earth's uppermost layers by rhetorical strength:

-the crust and the uppermost mantle (i.e. mantle lithosphere) are mechanically strong -the crust and mantle lithosphere comprise the lithosphere -the lithosphere sits atop the weaker athenosperhe, which is part of the upper mantle -techtonic plates are broken sections of the stronger lithosphere -the boundary between the crust and the mantle lithosphere is the Mohorovicic discontinuity -the boundary between the lithosphere and athenosphere is called the LAB

What happens when continents collide?

1. Closure of an ocean basin 2. Continental underthrusting 3. Intracontinental deformation

Two types of natural disasters:

1. Disasters induced by geological processes 2. Climate-related disasters

There are 3 types of plate boundaries:

1. Divergent boundaries 2. Convergent boundaries 3. Transform boundaries

What is the definition of plate tectonics? The process is characterized by three attributes:

1. Horizontal motion of rigid plates on a spherical surface 2. A kinematically-linked global network of moving plates 3. Recycling of the lithosphere through subduction and sea floor spreading

Layers of the earth:

1. Inner core (solid iron-nickel alloy; 70% of the size of the moon) 2. Outer core (liquid iron-nickel alloy)

There are three types of convergent plate boundaries (& they are distinguished by the type of crust involved)

1. Oceanic- Oceanic (>40* subduction) 2. Oceanic- Continental (>40* subduction) 3. Continental- Continental (<40* underthrusting)

Why aren't volcanoes associated with continent-continent convergence? -Both plates are too buoyant to sink into the asthenosphere. -Volcanoes are not associated with convergent plate boundaries. -The continental plate isn't hot enough to cause volcanoes. -Volcanoes only occur on islands in the ocean and not on land. -Rising magma from melted plates can't break through continental crust.

Both plates are too buoyant to sink into the asthenosphere

How fast do tectonic plates move?

Plates move at different rates, but typically few cm/yr

In general, where do earthquakes AND volcanic eruptions occur? Choose all that apply. -away from plate boundaries -transform plate boundaries -convergent plate boundaries -divergent plate boundaries

Convergent plate boundaries & Divergent plate boundaries

How do plates move at convergent plate boundaries? -Plates move toward one another. -Plates do not move. -Plates move apart. -Plates slide past one another.

Plates move toward one another

What causes melting of material under divergent plate boundaries? -melting of rock -recompression of rock -freezing of rock -decompression of rock

Decompression of rock

Where would you find ridge-push, a possible mechanism for driving the motion of tectonic plates?

Divergent boundary

Pangaea refers to the enormous single ocean that was produced when all of the continents were assembled. True or False

False. Pangea is a supercontinent.

How fast do fast plates move?

Fast plates move at the rate of hair growth -> 1 cm/yr (e.g. Pacific plate)

How do plates move at transform plate boundaries? -Plates slide past one another. -Plates move toward one another. -Plates move apart. -Plates do not move.

Plates slide past one another

We feel seismic waves as __________.

Ground motion or shaking.

Mantle-

In comparison to the lithosphere, the mantle is plastic, much like playdough

What is the order of the layers of the earth from inside to the outside?

Inner core, outer core, mantle, crust

To combat risk associated with hazards, we apply __________.

Mitigation

Data-based Hazard Mitigation-

Mitigation policies based on empirical evidence (data based on observation, experimentation, and making/testing hypotheses)

What forms at divergent plate boundaries? -new oceanic lithosphere -new continental lithosphere

New oceanic lithosphere

Which type of faulting is associated with the development of new ocean floor? -reverse faulting -normal faulting -transform faulting -back faulting -front faulting

Normal faulting

Normal Fault (divergent plate boundary):

One side of the fault moves in the down dip direction

How do plates move at divergent plate boundaries? -Plates move toward one another. -Plates slide past one another. -Plates move apart. -Plates do not move.

Plates move apart

Convergent Plate Boundaries-

Tectonic plates move towards each other

Why is India being forced under Asia?

The Indian continent is OLD and COLD and therefore more dense than the HOT and WEAK Asian continent

Mitigation-

The action of reducing the severity or damage provided by a natural hazard.

Earth's uppermost layers by composition:

The chemical composition of earth's layers controls their densities: -Crust- 2.7-2.9 g/cm3 -Upper mantle- 3.3-4.4 g/cm3 -Lower mantle- 5 g/cm3

Mantle lithosphere-

The mantle lithosphere is weaker than the crust despite being part of the lithosphere

Volcanism does not typically occur at __________ boundaries.

Transform

Why are volcanoes NOT found at transform boundaries? -Transform boundaries cause increases in temperature that exactly offset decreases in pressure of the mantle. -Transform boundaries cause changes to the pressure, temperature, or composition of the mantle. -Transform boundaries do not cause changes to the pressure, temperature, or composition of the mantle. -Transform boundaries cause decreases in temperature that exactly offset increases in pressure of the mantle.

Transform boundaries do not cause changes to the pressure, temperature, or composition of the mantle.

In California, Los Angeles is slowly moving toward San Francisco because the two cities are located on two different tectonic plates with a transform plate boundary in between. True or False

True

What would you NOT expect to see at locations where tectonic plates are sinking? -Subduction of oceanic lithosphere -Undersea mountain range that wraps around the Earth like seams of a baseball -Magma -Earthquakes -Volcanoes

Undersea mountain range that wraps around the Earth like seams of a baseball

Where do most divergent boundaries originate? -at transform boundaries -at mid-ocean ridges -at continental margins -within continents -at subduction zones

Within continents

The slow movement of the lithosphere is: -a key feature in the theory of plate tectonics caused by the gravitational attraction from the Moon -speeding up because of human-induced changes -responsible for earthquakes but not volcanoes.

a key feature in the theory of plate tectonics.

Which tectonic plate boundary is associated with the following features: major earthquakes; no volcanoes; large and high mountain chain is formed? Himalayan Mountains are a geographic example. -divergent plate boundary -convergent plate boundary (subduction zone) -convergent plate boundary (collision zone) -transform plate boundary -hotspot

convergent plate boundary (collision zone)

Which tectonic plate setting is associated with the following features: great earthquakes; explosive volcanic eruptions; oceanic plate sinks into mantle and remelts? Andes Mountains are a geographic example. -divergent plate boundary -convergent plate boundary (subduction zone) -convergent plate boundary (collision zone) -transform plate boundary -hotspot

convergent plate boundary (subduction zone)

Elastic Rebound Theory-

explains the occurrence of earthquakes along active faults.

Normal (divergent) faults are associated with _________ and ________.

extension and rifting

Tectonic plates move about as fast as -a tortoise walks -fingernails grow -hotspot -car moves on a city street -a swallow flies.

fingernails grow

Volcanism occurs not only at plate boundaries, but also at intra plate settings called ___________.

hotspots

Divergent plate boundaries initiate as an ________________.

interplate rift zone.

Which of the following hazards would you expect to see at a transform plate boundary? -Large earthquakes; no volcanoes; flooding if the plate boundary is hilly -Large earthquakes; no volcanoes; landslides and flooding due to the large plateau of very high mountains -Moderate strength earthquakes; non-explosive volcanic eruptions; flooding if volcanoes erupt underwater such as in Iceland -Large earthquakes; explosive volcanic eruptions; landslides and flooding due to long chain of volcanic mountains

large earthquakes; no volcanoes; flooding if the plate boundary is hilly

In general, where do volcanoes form in subduction zones? -on the subducting plate, away form the convergent boundary -on the subducting plate, at the convergent boundary -on the overriding plate, at the convergent boundary -on the overriding plate, away form the convergent boundary

on the overriding plate, away form the convergent boundary

Oceanic crust, continental crust, lithosphere are the _____ layer.

strong

We know about Earth's layers because of ____________________.

the propagation of seismic waves