Burst Tumuli

As inflation occurs within the core of a pāhoehoe flow, a tumulus (http://volcanoes.usgs.gov/images/pglossary/tumulus.php), or domed hill, can form. Occasionally the pressure within the flow can exceed the strength of the pāhoehoe crust, resulting in an outpouring of lava from the core of the tumulus. Lava burst from this tumulus, left side of photo along the skyline, approximately 35 yards downslope of the cemetery. A rocky block, presumably from the top of the tumulus, rests where the outpouring of lava began.