[sonofagun]

What’s the norm for life 5,000 feet below the surface?

Pretty bleak, I imagine.

However, ABC kept flashing videos of a beautiful coral reef with gorgeous tropical fish in very bright ambient light as a comparison.

[blackdog]

BTW, diatoms have very dense skeletons. In order to regulate boyancy while alive, they produce oil and increase or decrease the amount inside their cell walls to balance their depth in the water. When they die, the oil is dispersed into the marine environment.

Varients of these little fellas are what they are growing to commercially harvest their oil.

In a hundred years any oil down there will have been eaten by bugs or broken down into simpler carbon chains, and will sit capped quite neatly under a few feet of dead diatoms.