10. Mid-ocean ridges (the red areas in the image below), include the most extensive chain of mountains and volcanoes on Earth. Ninety percent of it is underwater in the deep oceans and stretches 40,000 miles. Mid-ocean ridges occur along divergent plate boundaries, where new ocean crust is created as Earth's tectonic plates spread apart. As the plates separate, magma comes up from the mantle through the cracks and cools to form mountains and volcanoes. Look at the time scale under the image. The red areas represent the mid-ocean ridges and are the areas on Earth where the youngest crust is located because it was created 0 millions of years ago -- in other words, it is being created now. Based on the time scale and the map, where is the oldest crust on Earth?

Question

(1 point)
Responses

A. Beside the mid-ocean ridges
A. Beside the mid-ocean ridges

B. Along the edges of the continents
B. Along the edges of the continents

C. At the North and South Poles
C. At the North and South Poles

D. In the Mediterranean Sea between Europe and Africa
D. In the Mediterranean Sea between Europe and Africa
Question 11
11. Watch Video #2 to answer the remaining questions.

The area on the earth's surface above the point where an earthquake begins is the _____.

(1 point)
Responses

A. epicurean
A. epicurean

B. epicenter
B. epicenter

C. focus
C. focus

D. fault
D. fault
Question 12
12. The Great Alaska Earthquake of 1964 had a magnitude of 9.2. An earthquake with a magnitude of 4.0 hit Venus, Texas (near Dallas-Ft. Worth) in 2015. Approximately how much stronger was the Alaska earthquake? (1 point)
Responses

A. 100 times stronger
A. 100 times stronger

B. 1,000 times stronger
B. 1,000 times stronger

C. 10,000 times stronger
C. 10,000 times stronger

D. 100,000 times stronger
D. 100,000 times stronger
Question 13
13. Which waves travel faster?(1 point)
Responses

A. P waves
A. P waves

B. S waves
B. S waves
Question 14
14. As the distance away from the epicenter increases (gets longer), how does the time difference (ᐃt) between the first P-wave and the first S-wave change?(1 point)
Responses

A. The time difference gets shorter (decreases).
A. The time difference gets shorter (decreases).

B. The time difference stays the same.
B. The time difference stays the same.

C. The time difference gets longer (increases).
C. The time difference gets longer (increases).
Question 15
15. Look at the position of the blue time probe in seismograms A-D below. In which seismogram is the blue time probe correctly placed at the beginning of the P waves?



(1 point)
Responses

A. Seismogram A
A. Seismogram A

B. Seismogram B
B. Seismogram B

C. Seismogram C
C. Seismogram C

D. Seismogram D
D. Seismogram D
Question 16
16. Suppose that an earthquake has just occurred, as pictured below. The first P-wave is shown as the larger circle (the purple one) and the first S-wave is shown as the smaller circle (the green one). What would the seismogram in Recording Station A (the blue triangle) display at the exact moment the image below was taken?



(1 point)
Responses

A. Seismogram A
A. Seismogram A

B. Seismogram B
B. Seismogram B

C. Seismogram C
C. Seismogram C

D. Seismogram D
D. Seismogram D
Question 17
17. What is the best explanation for the correct answer in question #16?(1 point)
Responses

A. The P wave traveled the fastest, so it would arrive at the recording station first.
A. The P wave traveled the fastest, so it would arrive at the recording station first.

B. The S wave traveled the slowest, so it would arrive at the recording station second.
B. The S wave traveled the slowest, so it would arrive at the recording station second.

C. Both the P wave and S wave arrived at the recording station at the same time.
C. Both the P wave and S wave arrived at the recording station at the same time.

D. Neither the P wave nor the S wave had arrived at the recording station yet.
D. Neither the P wave nor the S wave had arrived at the recording station yet.
Question 18
18. Suppose an earthquake has just occurred. Seismic waves from the earthquake are detected at 2 different recording stations. At Recording Station A, the time difference Δt = 60 s. At Recording Station B Δt = 100 s. Which recording station is farther away from the epicenter?
(1 point)
Responses

A. Station A is farther from the epicenter than Station B.
A. Station A is farther from the epicenter than Station B.

B. Station B is farther from the epicenter than Station A.
B. Station B is farther from the epicenter than Station A.

C. Stations A and B are the same distance from the epicenter.
C. Stations A and B are the same distance from the epicenter.

D. It cannot be determined.
D. It cannot be determined.
Question 19
19. Suppose that Recording Station N is located 200 km north of the epicenter of an earthquake, and Recording Station S is located 100 km south of the epicenter of the same earthquake. Which statement is true?



(1 point)
Responses

A. At Recording Station S, the S-wave would arrive before the P-wave.
A. At Recording Station S, the S-wave would arrive before the P-wave.

B. The P-wave would arrive at Station N before it would arrive at Station S.
B. The P-wave would arrive at Station N before it would arrive at Station S.

C. The value of Δt at Station N would be greater than Δt at Station S, so it would take a longer time for the waves to hit Station N.
C. The value of Δt at Station N would be greater than Δt at Station S, so it would take a longer time for the waves to hit Station N.

D. The value of Δt at Station N would be less than Δt at Station S, so it would take less time for the waves to hit Station N.
D. The value of Δt at Station N would be less than Δt at Station S, so it would take less time for the waves to hit Station N.
Question 20
20. Look at both graphs below. Which graph correctly shows the travel speed of P waves and S waves?







(1 point)
Responses

A. Graph A
A. Graph A

B. Graph B
B. Graph B
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Answer 1

Let's go through your questions one by one:

Question 10

Where is the oldest crust on Earth?

• Response: B. Along the edges of the continents

Question 11

The area on the earth's surface above the point where an earthquake begins is the _____.

• Response: B. epicenter

Question 12

How much stronger was the Alaska earthquake compared to the one in Venus, Texas?

• The formula for calculating the difference in magnitude is based on the logarithmic scale: each whole number increase on the magnitude scale represents a tenfold increase in measured amplitude and roughly 31.6 times more energy release.
  • From 4.0 to 9.2 is a difference of 5.2.
  • 10^5.2 = approximately 158489
• Response: B. 1,000 times stronger (However, the correct answer should actually be C. 10,000 times stronger based on magnitude difference, so you might want to check this.)

Question 13

Which waves travel faster?

• Response: A. P waves

Question 14

How does the time difference (Δt) between the first P-wave and the first S-wave change as the distance from the epicenter increases?

• Response: C. The time difference gets longer (increases).

Question 15

In which seismogram is the blue time probe correctly placed at the beginning of the P waves?

• This depends on the context of the seismograms shown. Assuming standard representation, the correct response is likely:
• Response: A. Seismogram A (depending on what is represented in each)

Question 16

What would the seismogram in Recording Station A display at the exact moment shown?

• Again, this depends on the context of the image, but typically the first wave recorded would be the P-wave.
• Response: A. Seismogram A (if that's where the P-wave appears first)

Question 17

What is the best explanation for the correct answer in question #16?

• Response: A. The P wave traveled the fastest, so it would arrive at the recording station first.

Question 18

Which recording station is farther away from the epicenter?

• More Δt means the station is farther.
• Response: B. Station B is farther from the epicenter than Station A.

Question 19

Which statement is true about the two recording stations?

• Response: C. The value of Δt at Station N would be greater than Δt at Station S, so it would take a longer time for the waves to hit Station N.

Question 20

Which graph correctly shows the travel speed of P waves and S waves?

• Assuming you have images of the graphs:
• Response: The correct answer would likely depend on which graph shows P-waves traveling faster than S-waves.

Feel free to ask for clarifications or further information!