Laboratory Manual for Introductory Geology 4e

EXERCISE 18.2
Short-Term Changes in the Geosphere
Name:
Course:
Section:
Date:
Seafloor Spreading
Examine the map of the South Atlantic Ocean below.
0 800 1,600 2,400 3,200
Kilometers
(a) Using this map, measure the current distance between the indicated points on the coastlines of South America and
Africa, parallel to the oceanic fracture zones: miles ( km)
(b) This distance is growing because of seafloor spreading along the Mid-Atlantic Ridge. This spreading began in the
South Atlantic about 135 million years ago. Calculate the average spreading rate over the life of the ridge.
Average spreading rate: mi/yr 5 ft/yr 5 in./yr
(c) Based on the rate you calculated in question (b), how much wider will the South Atlantic be in 50 years?
feet ( m)
(continued )
476 CHAPTER 18 LOOKING TO THE FUTURE