Summer GEO005 Midterm

What are Earth's four layers?

crust, mantle, outer core, inner core

What is the crust's relative thickness?

Thin under the ocean, thicker under continents (40km to 70km)

What is the mantle's relative thickness?

About 2900km

What is the outer core's relative thickness?

About 2400km

What is the inner core's relative thickness?

About 1220km

How did the Earth acquire its internal heat?

The initial collision of matter in the universe.

Why is the interior of the Earth layered?

When forming, the higher densities went to the center closer to the center. When it cooled, the Earth locked in the layers.

Why is the outer core liquid?

It is hotter than the melting point of the Earth.

Why is the inner core solid?

It is under extreme pressure

What is the lithosphere?

Strong outer layer of the Mantle and Crust, makes the plate tectonics.

What is the asthenosphere?

Below the lithosphere, weak and able to move, causes the shaking of the tectonic plates.

What are the three pieces of evidence Alfred Wegner used to prove continental drift?

The edges of the continents fit together like puzzle pieces, glacial striations matched on different continents, and fossils of the same animal were found on both sides of the continent.

How do we know that the magnetic field has reversed multiple times?

Lava cooled in the ocean trenches has distinct patterns that change when the field changes.

What is a mid-ocean ridge?

The area in the ocean where new lithospheric crust is formed.

What is a subduction zone?

Where one lithospheric plate is dragged or pushed below another lithospheric plate.

What is a transform plate boundary?

When two tectonic plates slide past each other

What is a passive plate margin?

Not an active plate edge.

What is a supercontinent?

All of the continents connected, Pangea.

What caused the high topography of the Himalayas and Tibet?

Convergent boundary collisions.

What is the Wilson cycle?

The cyclical opening and closing of ocean basins caused by movement of the Earth's plates.

Can convection occur within a crystalline solid?

No!

What drives plate tectonics?

Mantle convection

What are the components of Earth's magnetic field?

The spinning of the iron inner core.

What would be the consequence of losing the magnetic field?

Compasses would break, the northern lights would move, animal migration would be thrown off

What is the largest earthquake to happen in the past 100 years?

1st: 1960 Chile 2nd: 1964 Alaskan Earthquake

What is elastic rebound?

The sudden return of deformed rock to its undeformed shape

What is stick-slip behavior?

The stop-start movement along a fault plane caused by friction, which prevents movement until stress builds up sufficiently

What is an asperity?

Rough spots along the fault that cause sticking when it moves

How do plates deform before a subduction zone earthquake?

The plate being subducted bends

How does a thrust fault occur?

There is compression in a subduction zone.

How does a normal fault occur?

An extensional setting like a mid ocean ridge.

How does a strike-slip fault occur?

When plates slide past one another

What's one big mistake movies make with earthquakes?

The earth does not split open and leave a gaping hole.

What is the P wave?

A body wave moving in a push-pull motion, travels through everything, fastest wave

What is an S wave?

A body wave that moves up and down, can't travel through liquid, and is second fastest.

What is a Love wave?

A surface wave that moves side to side within the earth. Last.

What is a Raleigh wave?

A surface wave that moves up and down within the earth, last.

How many seismographs do you need to locate an earthquake?

Three

How do we know the outer core is liquid and the inner core is solid?

S wave shadow zones

How are the earthquake magnitudes and shaking magnitudes related?

For every number the magnitude goes up, the shaking increases by ten

What is the max earthquake magnitude?

10.0

What is the influence of loose gravel in earthquake shaking?

It can become almost liquid.

What is the Mercalli Intensity Scale?

The shaking that people and buildings physically feel

Why are earthquakes felt more on the East coast than the West?

Seismic waves travel faster, and they have less enforced infrastructure

What is the relationship between the biggest magnitude earthquakes and the deadliest?

Usually the deadliest happen in densely populated areas

Why are earthquakes hard to predict?

They follow no specific pattern

What is forecasting an earthquake based on?

Possible precursors, like foreshocks

Why are earthquake precursors a problem?

They are impossible to confirm

Why did Italy send a seismologist to jail?

They did not predict a deadly earthquake, which is impossible to do.

How are GPSs used to predict how big the next earthquake is going to be>

They can measure slip-deficit rates

Why is there a high seismic issue in the midwest?

Faults in the middle of continents rarely go off but they are deadly.

Why are diagonal beams more resistant to earthquakes?

They sway with the motion of the quake.

What is forced resonance?

Humans impacting the amount of shaking a quake gives off.

How does an earthquake early warning system work?

A small but vital warning to get under a table or shelter.

How do subduction zones cause volcanoes?

Unmelted mantle is forced to the surface through convection, and the lack of pressure turns it to magma.

What is a wind-blown wave?

Short wavelengths, brief period, and no water mass behind them.

What is a tsunami wave?

Long wavelengths and a water mass buildup behind the front.

How do tsunami waves behave out at sea?

Long wavelengths, short, and move at a great speed.

How do tsunami waves behave close to shore?

Shorter wavelength, taller, and they slow down.

When do water waves break?

When the height of the wave is equal to the depth.

What earthquake cannot cause a tsunami?

Strike-slip.

Why would being a good swimmer not save you from a tsunami?

The tide and movement would be too strong.

How do we know about past tsunamis in Japan?

Tsunami stones were set up as a reminder to not build below, because a tsunami has occurred at that height.

How do we know about past tsunamis in Washington/Oregon?

Natural sand deposits that show when they were displaced.

How many people have been killed by tsunamis in the past 1000 years?

Several hundred thousand.

What does it mean if you feel shaking near the shore?

Head to high ground

Why does the sea level drop before a tsunami?

The waters are dragged out when the trough arrives before the crest.

Why should you not return to shore after a tsunami?

There are often multiple waves to a tsunami.

Why did so many people die in the 2004 Indian Ocean tsunami?

Lack of warning system and extra tall waves.

How does the DART tsunami early warning system work?

By measuring the pressure in the seafloor, they can send out alerts 15 minutes after earthquakes with size and path estimates.

What has the potential to create the largest tsunamis?

Rockslides, especially underwater.

How do the Hawaiian Islands generate tsunamis?

Underwater landslides.

What is most likely to cause a tsunami in the Atlantic?

Underwater landslides.

What caused the largest tsunami runup in the past 100 years?

An earthquake in Alaska caused a rockslide into a narrow inlet.

What are the three settings volcanic activity takes place?

Mid-ocean ridges, subduction zones, hot spots

What is NOT an ocean of magma below the crust?

The mantle

What can cause hot rock to melt?

Decreasing the pressure

How does melting occur at subduction zones and hot spots?

The rocks melt when you decrease the pressure.

How does melting occur at mid-ocean ridges?

Hydration-induced melting

Why do hotspots result in chains of volcanoes?

As the tectonic plate moves over the hotspot, it creates new volcanoes.

What is the Ring of Fire?

An area of earthquake and volcanic activity that surrounds the Pacific Ocean.

What is viscosity the measure of?

How easily a liquid flows

How do stratovolcanoes form?

From alternating layers of lava and pyroclastic flows

What leads to an effusive eruption?

Low viscosity magma, more diffused gas

What leads to an explosive eruption?

High viscosity magma, lots of built up gas

What happens to dissolved gas when it reaches the surface?

It separates, forming bubbles

What are the four types of explosions in least to most impactful?

Hawaiian, Strombolian, Volcanic, and Plinian

How many volcanic related deaths have there been for the past 500 years?

250,000

What causes the least and most amount of deaths from a volcanic situation?

Least - Lava flow

Most - Pyroclastic flow

What is volcanic ash?

Tiny grains of volcanic glass from magma sprayed into the air by gas pressure

What is a pyroclastic flow?

A dense, destructive mass of very hot ash, lava fragments, and gases ejected explosively

What is a lahar?

A mud made of water, ash, and volcanic outputs

Can volcanic eruptions be predicted?

Yes, but they aren't reliable

What is a harmonic tremor?

Seismic energy that is related to magma moving underground

Why was the eruption of Pompeii so interesting?

It was recorded.

Who is Pliny the Younger?

He was able to record the events of Pompeii as they happened.

What cannot be apparent before a volcanic eruption?

Lava chambers cannot be exposed

What does the VEI measure?

The volcanic explosion

What is the difference in size for each level of VEI?

They multiply by ten.

Why do geysers erupt but hot springs don't?

Geysers build up pressure from the magma chamber but hot springs constantly release pressure.