The African and South American continents are separating at a rate of about 3 cm per year, according to the ideas of plate tectonics. If they are now 5000 km apart and have moved at a constant speed over this time, how long is it since they were in contact?
A) 1.7 million years
B) 170 million years
C) 170 thousand years
D) 1.7 billion years

Question

Quizplus · Accepted Answer

To find the time since the continents were in contact, divide the distance by the rate of separation and convert the units appropriately. $5000 \, \text{km} = 5,000,000 \, \text{m}$. At a rate of $3 \, \text{cm/year} = 0.03 \, \text{m/year}$, the time is $5,000,000 \, \text{m} / 0.03 \, \text{m/year} = 166,666,666.67 \, \text{years}$, which rounds to approximately 170 million years.

The African and South American Continents Are Separating at a Rate