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