The north american and european plates of the
earth’s crust are drifting apart with a relative speed of
about 25 mm/yr. take the speed as constant and find when
the rift between them started to open, to reach a current
with of 2.9 x 10^3 mi.

Explanation:

It is given that,

The North American and European plates of the  Earth’s crust are drifting apart with a relative speed of  about, v = 25 mm/ yr

We know that,

Distance between them,

1 mile = 1609.34 meters

Let t is the time when  the rift between them started to open. Speed is given by distance travelled divided by time taken.

Since,

So,

or

t = 1.86 million years

Hence, this is the required solution.

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