# Volcano Watch — Kīlauea vents active but lava has slowed

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The episode 51 vents have been continuously active since early in the morning on July 27. The active vents are located just west of the Puu Oo cinder and spatter cone on the East Rift Zone of Kīlauea Volcano. Episode 51 has been characterized by intermittent activity since it began on March 7.

Kīlauea vents active but lava has slowed

(Public domain.)

The episode 51 vents have been continuously active since early in the morning on July 27. The active vents are located just west of the Puu Oo cinder and spatter cone on the East Rift Zone of Kīlauea Volcano. Episode 51 has been characterized by intermittent activity since it began on March 7.

The most recent flows did not reoccupy the tubes formed during the previous eruptive period, and the development of a new tube system has slowed the advance of flows. All activity is now confined to the south side of the low lava shield that formed during episodes 50 and 51, as shown by the stars on the figure. The flows are now beginning to advance downslope, mainly over aa flow erupted from Puu Oo in 1986. No structures are threatened by these or by future flows from the same vents.

The lava lake inside Puu Oo remains active at a depth greater than 200 feet below the rim of the cone. This lava lake glows at night, and its large plume can be seen from Highway 11, or from the lookout atop Puu Huluhulu on the Napau Trail in Hawaii Volcanoes National Park.

This past week, HVO sponsored a workshop in Hilo to develop a comprehensive plan to assess the earthquakehazards in the State of Hawaii. Scientists from a number of universities joined a group from the U.S. Geological Survey and developed an outline for a future action plan for Hawaii.

Earthquakes in Hawaii fall into three main groups: shallow earthquakes directly related to magma movement inside the volcanoes, intermediate-depth basal earthquakes that occur as the flanks of the volcanoes slide seaward across the underlying sea floor, and deep earthquakes caused by the bending of the outer layer of the Earth (the lithosphere) due to the load of the huge volcanoes. An earthquake located near Kahoolawe Island this past week was of this type.

Of these three types, the basal earthquakes are the largest in Hawaii, reaching maximum magnitudes of around 8.0, but they are restricted to the young volcanoes on Hawaii Island. The deep earthquakes can also be large (roughly up to magnitude 7.0) and can occur beneath or adjacent to the older islands in addition to Hawaii. These earthquakes pose some, as yet undetermined, hazard to the rest of the state and require considerably more study. Recent analysis of past earthquake activity based on reports of ground shaking and associated phenomena indicates that the hazard posed to Hawaii is larger than previously thought, and that much of the southern half of the island of Hawaii can experience strong ground shaking that might be appropriately redefined as seismic zone 4, instead of the current, less hazardous, zone 3. These seismic zones are mainly used to establish appropriate building codes for areas prone to damaging earthquakes.

On Thursday, the Center for the Study of Active Volcanoes at the University of Hawaii at Hilo sponsored a forum on earthquake, tsunami and volcano hazards in Hawaii. This forum provided an opportunity for scientists and engineers to directly inform the public about hazards in Hawaii and about ways to mitigate those hazards. This open communication among scientists, the public, and public officials is an essential ingredient in effectively mitigating the effects of future natural disasters. HVO appreciates the opportunity to present some of the results of our program to the public.