Joe and Patricia would NOT have lived through a steam plume...
I love this movie, but I think the most unbelievable thing in this movie is that the volcano shoots out a steam plume right after they jump, which ejects them from the volcano... If the plume were just room temperature smoke, they'd be fine, but it was superheated gas coming OUT of the volcano. A quick google says gas from a volcano erupting can be as much as 1800 degrees Fahrenheit. The two of them would have been either vaporized, or had the tissue straight up melted off their bones. :-P
It makes for a fun twist ending, sure... But it's beyond even "suspension of disbelief" IMHO... Just sayin. :-P