Geology topics

William Rison

Publications and source records attributed to William Rison.

2 recordsLinked to original sources

USGS2010

Lightning and electrical activity during the 2006 eruption of Augustine Volcano: Chapter 25 in The 2006 eruption of Augustine Volcano, Alaska

Lightning and other electrical activity were measured during the 2006 eruption of Augustine Volcano. We found two phases of the activity, the explosive phase corresponding to the explosive eruptions and the plume phase. We classified the lightning into three types, vent discharges, near-vent lightning, and plume lightning. Vent discharges are small, 10 to 100 m sparks, that occur at rate as great as 10,000 s-1 at the mouth of the volcano during the energetic explosive eruptions. The vent discharges were observed six different times. Near-vent lightning appears to develop upward from the volcanic cone into the developing column during explosions. This lightning is small, in the range of 1 to 7 km, and short, 0.01 to 0.1 s. The behavior of the near-vent lightning indicates an overall positive charge in the ejecta. The plume lightning resembled intracloud thunderstorm lightning. Often it was branched, spanned more than 10 km, and lasted more than 0.5 s.

Alaska↗

USGS2007

Electrical activity during the 2006 Mount St. Augustine volcanic eruptions

By using a combination of radio frequency time-of-arrival and interferometer measurements, we observed a sequence of lightning and electrical activity during one of Mount St. Augustine's eruptions. The observations indicate that the electrical activity had two modes or phases. First, there was an explosive phase in which the ejecta from the explosion appeared to be highly charged upon exiting the volcano, resulting in numerous apparently disorganized discharges and some simple lightning. The net charge exiting the volcano appears to have been positive. The second phase, which followed the most energetic explosion, produced conventional-type discharges that occurred within plume. Although the plume cloud was undoubtedly charged as a result of the explosion itself, the fact that the lightning onset was delayed and continued after and well downwind of the eruption indicates that in situ charging of some kind was occurring, presumably similar in some respects to that which occurs in normal thunderstorms.

Alaska↗