The Fascinating Rate of Spreading on the Nazca Plate

What was the rate of spreading 40–50 million years ago on the Nazca Plate off La Paz?

a. 4.7 cm/yr

b. 1.6 cm/yr

c. 7.9 cm/yr

d. 8.5 cm/yr

Answer:

The rate of spreading 40-50 million years ago on the Nazca Plate off La Paz from 24.5°S, 80°W to 21°S, 72.6°W was 4.7 cm/yr, option (a) is correct.

To calculate the rate of spreading, we can use the equation:

Rate of spreading = distance ÷ time

The distance between 24.5°S, 80°W, and 21°S, 72.6°W can be calculated using the Haversine formula, which gives a value of approximately 891 km.

The time period is 40-50 million years, which is equivalent to 40000000-50000000 years, or 4.0 × 10^7 - 5 × 10^7 years. Converting this to seconds gives a range of 1.3 × 10^15 - 1.6 × 10^15 seconds.

Using the equation, the rate of spreading can be calculated as:

Rate of spreading = 891 km ÷ (1.3 × 10^15 - 1.6 × 10^15 seconds)

Rate of spreading = 4.7 cm/yr