Lava flows are of two types, 'a'a and pahoehoe. The former is rough and spiny, while the latter is smooth, billowy, or ropy. They may vary in color from shiny black to dull brown. Pit Craters Collapses that are smaller than the summit caldera collapses are called pit craters. Halema'uma'u at Kilauea is an example.
Pit craters can occur both in the summit region and along rift zones.
The road was blocked by lava flows in 1986, reopened, and then blocked again in 1987. When groundwater reaches rock of sufficient temperature, steam forms. Air temperature and humidity affect the visibility of steam escaping from cracks in the lava flows, so the amount seen may vary considerably from day to day. Sulphur Banks Sulphur deposits, left where volcanic gases have seeped out with groundwater steam, may be seen in or near the caldera of Kilauea. The Hawaiians call these islands or holes in lava flows kipuka.