Good fun taking vulcanologists into the crater of Karkar Island in PNG. Over the 6000' lip, land on the crater floor, and look up in dismay as cloud closes off the crater. Listening for rumbles underfoot, thinking of ways to blast off through the cloud, cruise for a minute to get clear of the hill, and then descend the 6000' back towards sea level. Luckily the cloud shifted before Karkar did anything silly.