Question

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.

Answer 1

Use Xf=Xi+Vxt
(2.9x10^3)=0+(1.55x10^-5)t <------- need to convert 25mm/yr to miles (1mm=6.2137x10^-7)
Solve for t.
t=187,096,774 years

Answer 2

Step-by-step 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,
`1\ mm/yr=3.171* 10^(-11)\ m/s`

`v=7.927* 10^(-10)\ m/s`

Distance between them,
`d=2.9* 10^3\ mi`

1 mile = 1609.34 meters

`d=2.9* 10^3\ mi=4667098\ m`

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

`t=(d)/(v)`

`t=(4667098\ m)/(7.927* 10^(-10)\ m/s)`

`t=5.88* 10^(15)\ s`

Since,
`1\ s=3.17* 10^(-8)\ yr`

So,
`t=18.63* 10^7\ years`

or

t = 1.86 million years

Hence, this is the required solution.