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The seismograms were recorded at earthquake recording stations A, B, and C. The letters P and S on each seismogram indicate the arrival times of the P and S waves. At what time did the S-waves arrive at station A?

• 08:16:00

• 08:21:00

• 08:27:00

• 08:30:00

The seismograms were recorded at earthquake recording stations A, B, and C. The letters P and S on each seismogram indicate the arrival times of the P and S waves. A fourth station recorded the same earthquake. The P waves arrived, but the S waves did not arrive. Which of the following is the best explanation for the absence of the S wave?

• S wave was never transmitted by the earthquake

• It stopped when it reached a solid part of Earth’s interior

• It stopped when it reached the liquid part of Earth’s interior

• It traveled only on Earth’s surface and did not penetrate Earth’s interior

When two tectonic plates collide, the oceanic crust usually subducts beneath the continental crust because it is

• denser than the continental crust
• less dense than the continenetal crust
• thicker than continental crust
• thinner than than continental crust

If you visit a place in the Pacific known to be along converging plates, which of these should not expect to see?

• active volcanoes
• mountain ranges
• rift valleys
• volcanic islands

You are an oceanographer and want to map the ocean floor on the east coast of the Philippines. As you do your study, you noticed that there is a portion of the ocean floor which is relatively much deeper than the rest. What most likely is that deeper part?

• linear sea
• oceanic ridge
• rift valley
• trench

Which of the following is true about the distribution of active volcanoes, earthquake epicenters, and major mountain belts?

• They are evenly distributed along the Earth’s surface

• They are concentrated in the middle of tectonic plates

• They are randomly distributed across the Earth's surface

• A.  They are concentrated along the edges of tectonic plates.

Which of the following factors contributes to the distribution of active volcanoes, earthquake epicenters, and major mountain belts in relation to Plate Tectonic Theory?

• Climate patterns

• Human activities

• Plate boundaries

• Tidal forces

Why are there no P waves or S waves received in the P-wave shadow zone?

• P waves are absorbed and S waves are refracted by the Earth’s outer core.

• P waves are refracted and S waves are absorbed by the Earth’s outer core

• Both P and S waves are refracted by the Earth’s outer core

• Both P and S waves are absorbed by the Earth’s outer core

Why does the oceanic crust sink beneath the continental crust at the subduction zone?

• The oceanic crust has a greater density

• The oceanic crust is pushed from the ridge

• The continental crust has a denser composition

• The oceanic crust is pulled downward by Earth’s magnetic field.

Island arcs are where two plates collide beneath the ocean forming a chain of volcanic islands. Which type of plate boundaries has formed the Philippines as an island arc?

• strike and fault

• collision of two oceanic plates

• collision of two continental plates

• collision of oceanic and continental plates