What is inside the earth?

Question

A research company wants to drill through the Earths crust to the mantle. The drilling rig can reach down only 6 km. Where was you set up the drilling rig to drill into the mantle? Why?

Answer 1

The start of the Earth's upper mantle lies just beneath the crust, which on land is 35-75 km. So if you could only dig 6km, you will not be able to drill far enough to make it to the mantle. But, in the ocean the crust can be around 5 km, so starting your dig at the bottom of the ocean would allow you to reach the mantle.