Understanding how pahoehoe morphs into aa is more than just scientific curiosity because the two lava types move at different speeds and pose distinct hazards.

The mucky gunge resembled a certain type of lava referred to as "pahoehoe", which is observed at Hawaii's famous Kīlauea volcano.

It was followed by a grueling three-hour trek over a volcanic smorgasbord of chunky lava — ropy pahoehoe formations, cinder cones and a goulash of grit.

It produced two small pahoehoe flows, which paved over its a'a flow.

Kilauea, by contrast, is a shield volcano: Its magma is relatively low in silica and flows easily, oozing out in characteristic ropy flows called pahoehoe and thick, blocky flows called aa.