Volcano Watch — HVO and Hawai‘i County Civil Defense jointly track the June 27th lava flow

Currently, Darryl Oliveira (HCCD Administrator) flies early each morning to measure the flow's advancement and direction and to assess fire and smoke conditions. These observations are compiled in a report available to the public later the same morning at http://www.hawaiicounty.gov/active-alerts/.

HVO overflights are scheduled 3–4 times per week to complement the County flights, with additional flights as necessary. During the HVO flights, geologists map the perimeter of the flow from the air, take photos, video, and infrared imagery, and assess eruptive conditions along the flow and at Pu‘u ‘Ō‘ō. On at least one of these flights each week, we sample the lava to determine whether the chemistry of the lava is changing (it's not).

We also try to measure the volume of lava being erupted by estimating the amount of lava flowing through the June 27th lava tube. This low-precision method suggests that between about 300,000 and 500,000 cubic meters (55,000–92,000 gallons per minute) of lava are being erupted each day, which spans the long-term average for the eruption as a whole (since 1983).

Based on feedback from the public, it's clear that our maps are an important means of communicating information about the lava flow. Therefore, we'd like to offer some clarification of the information included in the maps. Each HVO map shows the current position of the June 27th lava flow relative to nearby structures. By comparing the current position with past flow positions, we estimate the flow's current advance rate, which has varied over the past week.

An important feature now included on HVO's maps is the calculated paths of steepest descent, shown as blue lines. These blue lines are not stream beds, but can be envisioned as the regional drainage pattern. In other words, they are the paths where any fluid, including lava, would be likely to flow.

In addition to thoroughly documenting the current position and advance rate of the flow, HVO scientists also recalculate the downslope paths from the newly mapped flow-front position to get the best sense of where the lava is headed. While the regional drainage pattern gives us a fairly good idea, it is based on a digital elevation model (DEM) that may have errors in it. With the new downslope path calculations, however, random variations of plus or minus 5 m (16 ft) elevation are added to the original DEM at random locations to see if, after thousands of runs, this "noise" significantly changes the downslope path.

The results from these secondary calculations do not differ significantly from the regional drainage pattern, but they do show us how some of the downslope paths can be connected in ways that may not be obvious in the regional map. This helps us to choose which one of the possible regional drainage lines is the preferred future lava-flow path. As part of the post-overflight maps, we now indicate that preferred path on a satellite image as a series of arrows that illustrate the next two weeks of time.

Based on the data we acquired during the overflight, HVO issues a forecast in the form of a Volcanic Activity Notice (VAN) that is posted on the HVO website along with the Kīlauea daily eruption update (http://hvo.wr.usgs.gov/activity/kilaueastatus.php). The VAN includes our best estimates of when the June 27th lava flow will reach significant infrastructures based on the flow's current advance rate. You can sign up to receive VANs, which are distributed via the USGS Volcano Notification Service (VNS), by subscribing to VNS at http://volcanoes.usgs.gov/vns/.

HVO products—maps, photos, videos, updates and VANs—can all be accessed online at http://hvo.wr.usgs.gov/activity/kilaueastatus.php, or through links listed in the yellow box on our homepage (http://hvo.wr.usgs.gov).

Our products evolve in response to the needs and requests from partner agencies and the public. We have received a lot of feedback, both positive and negative, via our email address, askHVO@usgs.gov, and continue to welcome constructive comments and suggestions.

We also encourage Puna residents to stay informed about the June 27th lava flow. As stated in last week's Volcano Watch article, while we are hoping for the best, we must also plan for the worst.

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Volcano Activity Update

The June 27th lava flow from Pu‘u ‘Ō‘ō remained active on Kīlauea Volcano's East Rift Zone. The active flow front was 16.2 km (10.1 mi) from the vent and 2.5 km (1.6 mi) from Apa‘a Street/Cemetery Road as of September 18 (the time of this writing), and moving in a northeasterly direction. Within the Pu‘u ‘Ō‘ō crater, glow was visible above several small lava ponds and outgassing openings in the crater floor.

The summit lava lake within Halema‘uma‘u Crater produced nighttime glow that was visible via HVO's webcam over the past week. The lava lake level ranged from 50 to 55 m (164–180 ft) below the rim of the Overlook crater.

There were no earthquakes reported felt on the Island of Hawai‘i during the past week.