Diamonds show depth of carbon cycle

Diamonds from 700 kilometres below the earth’s surface show the carbon cycle extends deep into the planet’s interior.

The diamonds contain impurities or “mineral inclusions"that are consistent with the composition of the earth’s oceanic crust. This demonstrates that the oceanic crust sank (or subducted) into the lower mantle and that material, including carbon, is recycled between layers.

Scientists have long speculated that the carbon cycle extends beyond the earth’s surface, but the recent finding provides the first evidence.