Today, lenticular altocumuls clouds surrounded the peak of Mt. Erebus. The heat escaping from the cauldron had a neat effect on the cloud formation. The bottom picture was taken about 5 minutes from after the top picture. My guess is that the warm air escaping from the volcano was pushing the air pocket higher up, altering the altitude at which the water vapour condensed into water droplets, hence the reason why there is a higher small cloud right above the cauldron.