Chapter Four Questions

Occur almost exclusively in the interior of the colder oceanic lithosphere, the heart of the subducting slab.

At depth between 100 and 700 km, where do earthquakes occur?

180 million years.

At present rates, how long would it take subduction to subduct ocean crust equivalent to the entire surface area of the earth?

Yes, the seismic gap was filled.

Did the 2011 Japan Earthquake fill a seismic gap?

Fracturing and faulting -The magma rises up through cracks and makes earthquakes.

How do rift valleys form?

The active volcanoes above the subducting plates testify that subducting is still occuring.

How do we know that active subduction is occurring of the coast of the Pacific Northwest?

If segments of one-fault have moved recently, then it seems reasonable to expect that the unmoved portions will move next and thus fill the gaps.

How does the seismic-gap method work in predicting earthquakes?

Iceland-180 million years Africa- 25 million years difference=155 million years

How does the spreading center in Iceland compare with that in northeast Africa (in years)

From a broad perspective, all these subparallel right-lateral, transform faults are part of the San Andreas plate boundary fault system carrying peninsular California to the Northwest.

How is seafloor spreading forcing California (West of the San Andreas Fault) to move northward?

Arabian pate being shoved into Eurasia- Rigid continental rocks of the Arabian plate are driven like a wedge into the stiff underbelly of Eurasia.

How is seafloor spreading in the Red Sea causing great earthquakes in Iran and Turkey?

Because it is at a spreading center BOTH DIVERGENT BOUNDARIES OF THE OLD WORLD, NEW WORLD- CALIFORNIA

How is the gulf of California similar to the Red Sea and the Gulf of Aden?

East-west oriented transform faults between the spreading center segments.

In Iceland, on what type of fault do large earthquakes occur?

Convergent or push-together motions at subdution zones and in continent-continent collisions cause rocks to fail in compression.

On what type of plate boundaries do gigantic earthquakes occur?

Irregular plate boundaries

On what type of plate boundaries do larger earthquakes occur?

Divergent or pull-apart motion at spreading centers.

On what type of plate boundaries do smaller earthquakes occur?

Eastern: Straighter and holds shallow, alkaline lakes and volcanic peaks. Western: Curved and has many deep lakes.

The East African Rift Valley has 2 major branches, how does the eastern rift differ from the western rift?

Dead Sea, Sea of Galilee, Gulf of Aquba.

What 3 bodies of water lie in the rift valley formed by this fault in the Holy Land?

Seismic waves, mud shaking, tall buildings

What 3 things had similar resonance that greatly increased the damage in Mexico City?

Subducted beneath Asia by about 40 million years ago?

What happened to the 3,000 miles of seafloor that once lay between India and Asia?

The first segment of the pacific spreading center collided with N. America at about the site of LA today. The spreading centers to the N+S still operated as before. A transform fault, specifically the ancestor of the S.A. fault connected the N. + S. spreading centers.

What happened to the Pacific Spreading Center after it collided with the North American Plate about 28 million years ago?

When earthquake clusters occur, -multiple earthquakes- a lot of seismic gaps filled in.

What happens when an earthquake cluster occurs?

As the Atlantic ocean basin widens further, both N. and S. America move westward into the Pacific Ocean basin, helping reduce its size. -MID ATLANTIC SPREADING ZONE

What is causing the North American and South American plates to move westward?

As the Arabian plate pushes farther into Eurasia, Turkey is forced to move westward and slowly rotate counterclockwise in escape tectonics. Bonded by the N. Anatolian Fault in the N. and E. Anatolian Fault in the Southeast, Turkey is squeezed westward like a watermelon seed from between your fingers.

What is escape tectonics and how is Turkey being impacted by seafloor spreading in the Red Sea?

The Fault Rupture is to keep moving to the West.

What is happening along the North Anatolian Fault and why is this increasing the danger that Istanbul will experience a large earthquake?

Dead Sea Fault Zone.

What is the San Andreas Fault of the Holy Land?

Forcing Indochina to escape to the southeast and is driving a large block of China to the east.

What is the collision between India and Asia doing to Indochina and a large block of China?

Imperial Valley=only part of the United States that sits on opening sea floor.

What is unique about the Imperial Valley?

Highest-standing continental area on earth.

What is unique about the Tibetan Plateau and how it was formed?

Land=composed of deposits of windblown silt and fine sand=little cohesion- many homes dug in caves-land=like a liquid-people were entombed.

What unique circumstance killed so many people in the 1556 China Earthquake?

The most tragic event was when 40,000 people attempted to escape the flames by crowding into a 250 acre garden-all died from fire -38,000 died.

What was possibly the most tragic event in the 1923 Tokyo Earthquake?

Chile 1960- SUBDUCTION OF NAZCA PLATE

What was the biggest earthquake ever measured on earth; what caused it?

Alaska, 1964- duration of strong ground shaking was lengthy-induced many avalanches, landslides, ground settlements, and a TSUNAMI

What was the second biggest earthquake ever measured and what agent killed the most people?

Annual growth records of trees- Tsunamis in Japan submerged trees

What were the two lines of evidence for a large earthquake in 1700 in the Pacific Northwest?

Canada, California, South of New Zealand.

Where are these 3 transform faults located: Queen Charlotte, San Andreas, Alpine?

The greatest earthquakes in the world occur where plates collide, -Convergent-subducted or upheaval.

Where do the greatest earthquakes in the world occur; why?

Form at the top of a mantle plume. Where 3 plate edges touch!

Where do triple junctions form?

They are at transform faults and at subduction/collision zones. The expanded volumes of warm rock in the oceanic ridge systems have a higher heat content and a resultant decrease in rigidity. These heat-weakened rocks do not build up and store the huge stresses necessary to create great earthquakes.

Why are earthquakes on spreading centers less frequent and smaller than other plate edges?

Fault movements and the huge volume of sediment deposited by the Colorado River hold back the waters of the Gulf of California.

Why isn't the Imperial Valley under the sea?

Soft sediment foundations= duration of strong ground shaking increased due to seismic energy trapped within the soft sediments.

Why was Mexico City in 1985 so badly damaged by an earthquake whose epicenter was over 200 miles distant from the city?

Lived in poorly constructed concrete buildings.

Why were so many people killed by the 2010 Haiti earthquake?