Real duh moment

In theory you have to start with something to spoil it. So no spolier alerts.

First group.........met the volcanoe up close and personal. Missing presumed dead.

Second group, assumably scientists, aware of first group missing "a few days before" and we see lave, at the time the first group goes missing.........why couldn't the 2nd group see the lava we saw........and know that, they needed to keep the helo overhead?

The swiss cheese list of plot glitches, is so lengthy, its not worth trying to catalog them.