Base your answer to question 2 on the map below, which shows the location of the Peru Chile Trench

2. The Peru-Chile trench marks the boundary between the:

A) Pacific Plate and the Antarctic Plate

B) Nazca Plate and the South American Plate

C) North American Plate and the Cocos Plate

D) Caribbean Plate and the Scotia Plate

Correct Answer: Option B - Nazca Plate and the South American Plate

The South American Plate is a tectonic plate covering the continent of South America and extending eastward to the Mid-Atlantic Ridge. The easterly side is a divergent boundary with the African Plate forming the southern part of the Mid-Atlantic Ridge. The southerly side is a complex boundary with the Antarctic Plate and the Scotia Plate. The westerly side is a convergent boundary with the subducting Nazca Plate. The northerly side is a boundary with the Caribbean Plate. At the Chile Triple Junction in Taitato-Tres Montes Peninsula an oceanic ridge, the Chile Rise, is subducting under the South American plate.

The Nazca Plate is an oceanic tectonic plate in the eastern Pacific Ocean basin off the west coast of South America. The eastern margin is a convergent boundary subduction zone under the South American Plate and the Andes Mountains, forming the Peru-Chile Trench. The southern side is a divergent boundary with the Antarctic Plate, the Chile Rise, where seafloor spreading permits magma to rise.

Hence, options A, C and D are incorrect.

Base your answer to question 3 on the map below, which shows the location of the Peru Chile Trench

3. In which diagram below do the arrows best represent the motions of Earth’s crust at the Peru-Chile trench?

A)

B)

C)

D)

Correct Answer: Option A

The Peru-Chile Trench, also known as the Atacama Trench, is an oceanic trench in the eastern Pacific Ocean, about 160 kilometers (100 mi) off the coast of Peru and Chile. It reaches a maximum depth of 8,065 meters (26,460 ft) below sea level in the Richards Deep and is approximately 5,900 kilometers (3,666 mi) long; its mean width is 64 kilometers (40 mi) and it covers an expanse of some 590,000 square kilometers (228,000 mi²). The trench is a result of the eastern edge of the Nazca Plate being subducted under the South American Plate. The trench subducts two seamount ridges; the Nazca Ridge and the Juan Fernández Ridge. Hence, option A has the best representation of this phenomenon and the other three options are incorrect.

Base your answer to question 4 on the map below, which shows the location of the Peru Chile Trench

4. Which observation provides the best evidence of the pattern of crustal movement at Peru Chile trench?

A) The direction of flow of warm ocean currents

B) The mineral composition of samples of mafic mantla rock

C) Comparison of rates of sediment deposition

D) The locations of shallow-focus and deep-focus earthquakes

Correct Answer: Option D - The locations of shallow-focus and deep-focus earthquakes

The focus (sometimes referred to as the hypocenter) is the point within a geological fault that is rupturing where the earthquake begins.  The epicenter is the point on the surface of the earth that is directly above the focus.  When the energy is released, the earthquake waves start at the focus, and then radiate out from there along the part of the fault that has ruptured.  Shallow-focus earthquakes are created if the focus is near the surface of the earth (between zero and forty miles deep) while deep-focus earthquakes are created if the focus is deep within the earth (between forty and four hundred miles deep).  Shallow-focus earthquakes are much more common than deep-focus ones, and they are usually larger, which in turn makes them more dangerous.  Shallow-focus earthquakes usually begin near an area where the crustal plates of the earth are moving against one another. Deep-focus earthquakes usually begin in places where one tectonic plate moves under another one, or subducts. Faults, which are places in the crust of the earth where rocks have moved (if those rocks slip, an earthquake occurs), are mainly created when the crust becomes stressed and slips suddenly, as the result of tectonic plates having moved.  The movement of tectonic plates is very slow, and pressure within the earth's crust builds up as  they collide or slide past each other.

The plate movement coincides with the deepening direction of earthquakes. i.e for the subducting plate.

Hence, options A, B and C are incorrect.

5. Approximately how long does an earthquake P-wave take to travel the first 6500 kilometers after the earthquake occurs?

A) 6 mins

B) 10 mins

C) 8 mins

D) 18.5 mins

Correct Answer: Option B - 10 min

From page 10 of the Earth Science Reference Tables, we have the following data:

Locate the P-wave line. Then locate 6500 km on the x-axis of the P and S-wave chart. Follow the 6500 line up to the P line, when it intersects follow the line to the left and locate travel time. In the above case it is 10 mins.

Hence, options A, C and D are incorrect.