We are at the end of the normal repose interval, the time of quiescence between eruptive periods. The COM lava field formed during eight eruptive periods with a recurrence interval averaging 2,000 years and it has been over 2,000 years since the last eruption. The constancy of the most recent output rates suggests that slightly over one cubic mile of lava will be erupted during the next eruption period. In the past, eruptions in the COM lava field have generally shifted to the segment of the Great Rift with the longest repose interval. Therefore, the next eruptive period should begin along the central portion of the Great Rift in the COM lava field, but may well propagate to the northern part of the monument in proximity to the loop road (Kuntz, et al, 1986). Initial flows, based on past history, will probably be relatively non-explosive and produce large-volume pahoehoe flows. Eruptions from potential vents on the northern part of the Great Rift may be comparatively explosive and may produce significant amounts of tephra, destroy cinder cones by both explosion and collapse, and build new ones (Kuntz, et al, 1986). As yet, no comprehensive volcanic hazard assessment or plan has been done for the Monument.

Table 1. Geoindicators (proxies for geologic processes).

H — HIGHLY influenced by, or with important utility

M — MODERATELY influenced by, or has some utility

L — LOW or no substantial influence on, or utility

* adjusted to reflect BLM input about grazing after the Monument expansion