Geo Exam 2
What is the intensity of an earthquake?
-measure of effects of an earthquake on people and buildings -shaking and damage -depends on EQ magnitude and population density, buildings, codes, ground materials, distance
Mountains and Volcanoes form at a convergent boundary when...
An oceanic plate subducts below a continental plate and the overriding plate gets pushed up.
If you find a plate boundary along the edge of an ocean next to a continent, what kind would it be?
Convergent
What kind of plate boundary do earthquakes normally occur?
Convergent
Which plate boundary creates the most dangerous volcanoes, largest earthquakes, and biggest mountains?
Convergent
What kind of plate boundary does subduction occur at?
Convergent plate boundary
Two situations in which a large-magnitude earthquake can have low intensity
If there is not a large population in the area or if the buildings are built on better ground material
Can earthquakes happen at all boundaries?
Yes but they are most common/largest at convergent
What is a mantle plume?
a circular column of magma that rises from deep within Earth
What is a Tsunami?
a giant wave created by vertical shift in ocean floor.
What is viscosity of magma?
a measure of materials resistance to flow
What are earthquakes?
a sudden slip on a fault, and the shaking caused by the split
At which type of tectonic setting would you expect the development of composite volcanoes?
an oceanic plate subducted beneath a continental plate
What is the intensity of an earthquake?
the measure of damage and deaths it caused.
What is peridotite?
the rock making up the mantle
What was Panthalassa?
the single ocean that existed after the Pangaean supercontinent formed
Melting occurs at a subduction zone primarily because...
it is at a mid-ocean ridge and experienced a change in pressure
What do we call mudflows produced by the melting of snow and glaciers on composite volcanoes?
lahars
Do silicrich (felsic) rocks melt at higher or lower temperatures than mafic rocks?
lower
At which type of tectonic setting would you expect the development of shield volcanoes?
mantle plumes
Where are most modern divergent plate boundaries found?
mid-ocean ridges
Which type of faulting is associated with the development of new ocean floor?
normal faulting
Where are continental volcanic arcs found?
on the overriding plate near a subduction zone
What are surface waves?
travel along earth's surface. They are the slowest
What are body waves?
travel through earth's interior. P(primary) waves are the fastest and S(secondary) waves are 2nd fastest
Earth's magnetic field switches polarity at irregular time intervals.
true
What is a hot spot?
unusual source of heat in upper mantle. Plates move over, get melted, form volcanoes
What are seismic waves?
vibrations caused by an EQ
The force pushing viscous magma to extrude during an eruption comes from what?
volatiles
What features can form on a planet if it has a hot, molten interior?
volcanic lava flows
How an earthquake happens
-Friction causes most faults to "stick" -rocks are elastic and stress builds up -After decades, stress overcomes friction, causes to snap
On average, how many damaging earthquakes occur each year?
1,000
What are three factors that determine the violence of a volcanoe?
1. Composition of the magma 2. temperature of the magma 3. dissolved gases in the magma
Where the lithosphere goes to die... 3 types:
1. Ocean-continent: denser ocean plate slides under continent (subduction) 2. Ocean-ocean: same as ^ 3. Continent-Continent: neither subducts. this creates big mountains
What are the three ways rocks can melt?
1. When temperature increases 2. Pressure decreases 3. Chemical Reaction: water is added to the rock
What are the 2 types of surface waves. explain them
1. rayleigh waves- result in vertical movement of surface 2. love waves- produce a side-to-side movement
How much would ground motion increase between a magnitude 4.5 and 5.5 earthquake?
10 times as much
When did Pangea break apart?
200 millions years ago
How much is the movement of plates away from each other at divergent boundaries annually?
5 cm per year
A volcanic arc is formed when which of the following conditions exists?
A piece of oceanic crust is subducted below continental crust.
If you were examining a map, what would you look for to indicate that subduction is happening?
A trench
Rocks melt at convergent boundaries because of:
Addition of water
Where do earthquakes occur?
Along plate boundaries where plates move
What were the most common plate boundaries when Pangea was being assembled
Continent-continent collision
How are continental rift magmas and continental arc magmas different?
Continental arc magmas are more viscous than continental rift magmas.
If you find a plate boundary in the middle of an ocean away from an edge, what type of plate boundary is it most likely to be?
Divergent
How are elastic rebound and elastic deformation different?
Elastic deformation causes objects to bend, whereas rebound causes objects to return to their original shape.
Where is the oldest crust found in relation to a plate boundary? (closer or farther from boundary)
Farther away from the boundary
What type of lava would be viscous (thick)?
Felsic
Which of the following events allows rocks on either side of a fault to rebound elastically, causing an earthquake?
Friction along the fault plane is overcome.
What are the two reasons volcanoes form?
Hot spots and plate tectonics
Two situations in which a small-magnitude earthquake can have high-intensity
If there is a large population in the area and the buildings are built on softer ground and not good building codes.
What causes an ocean trench?
Its the place where two plates meet on a convergent boundary and one subducts.
What type of lava lets gasses escape easily?
Mafic
What type of lava would be runny?
Mafic
What is the difference between magma and lava?
Magma is molten rock below the surface and lava is molten rock at the surface
What is the composition of the outer core of the earth?
Metal and liquid
How do volcanoes form?
When rocks melt, magma is less dense then surrounding rock so it rises straight through the crust forming magma chambers for volcanoes.
What kind of lava would a shield volcanoe produce?
Runny, mafic, basalt. Peaceful eruption
Magma occurs in the uppermost mantle because..
That's where temperatures are high enough and pressures are low enough
What is the magnitude of an earthquake?
The amount of energy released as the rock breaks
What is a divergent plate boundary?
When two plates are moving away from eachother
What are transform boundaries?
When two plates slide past each other
When two plates composed of oceanic lithosphere collide, what determines which one will subduct?
The plate composed of older, cooler lithosphere will subduct
The oldest oceanic crust is 180 million years old while the oldest rocks on the continent is 4 billion years old. why?
The rocks of the continents are never destroyed by subduction under a continent
Thermodynamics
Thermal energy-energy of vibrating atoms Heat- total thermal energy of all the atoms in a substance Temperature-the average thermal energy of all the atoms in substance Entropy- amount of disorder/disorganization in a system Melt-increase the entropy
What kind of lava would a composite volcanoe produce?
Viscious, felsic, rhyolite, explosive eruption
What is a convergent plate boundary?
When plates are moving together.
What causes ridges in the ocean?
When rocks are hotter so they are less dense and are higher
Elastic Rebound
When rocks can store energy until the stress becomes too much and they break
Which type of force is responsible for reverse fault formation?
compressional force
What type of stress is most directly associated with convergent boundaries?
compressional stress
85% of volcanoes are at what kind of plate boundary
convergent
What causes melting of material under divergent plate boundaries?
decompression of rocks
Rocks melt at divergent boundaries because of:
decreasing pressure
Which type of plate boundary is most closely associated with the formation of new ocean floor?
divergent
What features can form on a planet if it has an atmosphere?
dunes
Most earthquakes are the result of movement along which feature?
faults
What is a fault?
fractures along which rocks move
Describe a mafic rock.
has a lot of iron and magnesium that break up the silicon and oxygen chains
Describe a felsic rock.
has a lot of silicon and oxygen chains and very little iron and magnesium
What features can form on a planet with any characteristics?
impact craters
Rocks melt at hot spots because of:
increased temperature
Which type of force is responsible for normal strike-slip formation?
shear force
What type of stress is most directly associated with transform faults?
shear stress
Which of the following describes the type of deformation experienced by rocks before an earthquake?
slow deformation
What features can form on a planet if it has liquid on the surface?
stream beds
Which type of fault has NO vertical motion of rocks associated with it?
strike-slip fault
Which type of force is responsible for normal fault formation?
tensional force
What type of stress is associated with divergent boundaries?
tensional stress
