In 1959, the Kilauea Iki vent erupted throwing magma 1900 feet into the air and filling the bottom of the crater with a lake of molten lava. 53 years later, this lake’s surface has solidified and the National Park Service has kindly built a 4 mile hiking trail that takes you around half the crater wall then down and across the surface of the lake itself. The rock down there is still hot to the touch with molten magma only 400 feet or so beneath your feet. The surface is stressed and cracked due to the contraction of the lava lake and there is still very hot steam venting from many of the cracks.
Hiking across this is awesome and, frankly, rather scary! We did the hike a couple of days ago and this shot was taken from the rim of the crater on the following evening. Each of the “bubbles” you see here is probably 60 feet or so across and the lighter coloured section running diagonally left to right is the path of the trail.