system
Given the following post, respond as if you're commenting on Reddit:
human
How much mixing is there between layers of the Earth? Is a molecule 4,000 km down ever going to reach the surface?
gpt
Almost certainly not. The amount of material brought to the surface by volcanic activity and plate separation is minuscule compared to the volume of the material in those layers. Short of a huge collision with something like the moon, that molecule is unlikely to see the light of day before our core stops churning.