The Kings Bowl lava field, associated with the Craters of the Moon National Monument and Preserve on the Great Rift in Idaho, U.S.A., contains many explosive pits, the largest of which has a substantial field of ejecta blocks. These features were formed when lava supply diminished, the fissure was evacuated, and ground water entered. We have documented the properties of the ejecta block field: crater shape, the ejecta field to the west and the tephra field to the east, the vesicularity and density of the blocks, the block size distribution and the number of blocks per unit area as a function of distance from the crater, and the aspect ratios of the blocks. To the degree possible we compare the data to those of ejecta blocks at other phreatomagmatic craters on rifts especially, Deception Island, South Shetland Islands, and White Island, New Zealand, and find them similar. Many of the Kings Bowl ejecta characteristics can be described by relationships that have previously been published to describe ejecta blocks around impact craters. We have also performed ballistic and energy calculations to derive ejection velocities for the blocks consistent with our data. The “velocity exponent” b in the relationship d ∝ vi-b where d is ejecta size and vi is the initial ejecta velocity for our data is around −3.0 and in the range previously observed for impact ejecta (−3.7 to −0.32), although at the small end.