Found this interesting lecture on the exploration of the 150 mile long Lechiguilla Cave on YouTube.
Maybe this is the The future of conferences while coronavirus is strong. 
There is a lengthy preamble but the caving talk I found to be excellent.
https://youtu.be/yuXkohzyQ0A

YouTube is a wealth of information like this, once you get past the showoffs and conspiracy theorists.

Loads of filmed lectures and similar.