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Volcanowatch

October 5, 2006

A weekly feature provided by scientists at the Hawaiian Volcano Observatory.


Using Google Earth to determine Lava Flow Hazard Zones for Hawai`i County

Lava Flow Hazard Zones for Hawai`i County
Lava Flow Hazard Zones for Hawai`i County

Many of the questions asked of HVO staff members are about eruptions of Hawaiian volcanoes or basic Hawaiian geology. We also get lots of questions from property owners, insurance and mortgage companies asking what Lava Flow Hazard Zone a specific property is located in.

Over the last several years, we?ve tried to answer all those questions, because USGS staff defined and refined Lava Flow Hazard Zones for the county. The map shows the island divided into nine lava-flow hazard zones, based on the location of active vents, the frequency of past lava coverage, and the topography of the volcanoes (http://hvo.wr.usgs.gov/hazards/lavazones/main.html).

The current map was published as a paper product in 1992. The text accompanying the map states, ?Hazard zone boundaries are approximate and gradational. These boundaries are not specific enough to determine the absolute degree of danger at any particular site. Lava flow hazard maps are designed to show relative hazard across the Island of Hawai`i and are meant to be used for general planning purposes only.?

The printed map was not intended to be used at a scale necessary to identify individual parcels on a tax map. In 1995, a State law was passed requiring realtors to disclose all natural and man-made hazards affecting property offered for sale. Insurance companies and mortgage lenders commonly require the same information. Uncertain about how exactly to determine the hazard-zone designation, many people phoned their questions to HVO, Hawai`i County Civil Defense, and the Hawai`i County Planning Department. The Planning Department commonly referred the callers to HVO.

While the above use was never the intent in publishing the maps, we accept that the hazard zone information is required to comply with state law. In addition, the availability of digital mapping software (Geographic Information Systems or GIS) has completely changed the way maps are used. Instead of being stuck with a map at the scale at which it was printed, anyone with GIS software can now view any GIS map information at any scale ? even inappropriate ones.

The State law requiring full disclosure - and the public availability of the Lava Flow Hazard Map as a GIS layer (http://www.hawaii.gov/dbedt/gis/download.htm) - means that those with access to GIS software can now overlay the lava flow hazard zones and boundaries on the latest version of the County of Hawai`i tax maps to get this information for themselves. A GIS viewer can be accessed at http://gis.hawaii.gov/Website/OPGeneral/viewer.htm .

The difficulty with HVO personnel determining which Hazard Zone a particular parcel lies in is that we don?t have the most current County Tax Maps. The County of Hawai`i Planning Department has solved this problem by agreeing to include Lava Flow Hazard Zone information on the GIS CD that they distribute to anyone who asks. Just call 808-961-8288 and ask for the Zoning clerk, who will take your order for this CD. The cost is a minimal $5, and the CD is updated each quarter.

Of course, the requestor is still required to install and use the GIS browser software that comes with the CD. This can still be challenging for beginners.

Alternatively, very good, easy-to-use, web-based mapping software has recently become available for anyone who has internet connectivity and can operate a mouse. If you haven?t discovered it yet, Google Earth (http://earth.google.com/) is an amazing application that?s freely available. It contains enough high-quality earth surface imagery, you can use it to look for friends? or relatives? houses or any volcano anywhere in the world. And it?s become a common viewing platform for government agencies that release map data. For example, one can display anything, from current earthquakes (http://earthquake.usgs.gov/research/data/google_earth.php) to current Weather Service radar images (http://www.srh.noaa.gov/ridge/kmzgenerator.php).

This Volcano Watch Article announces the release of the first Google Earth mapping file made available by HVO: one that displays Lava Flow Hazard Zones for the County of Hawai`i on the Google Earth base. If you can find your house or even your neighborhood on Google Earth, you?ll be able to use this overlay to see what Lava Flow Hazard Zone you are in. Install Google Earth if you haven?t already done so and click on http://hvo.wr.usgs.gov/hazards/lavazones/HVO_LavaFlowHazardZones.kmz to view the Lava Flow Hazard Zones for Hawai`i County.

Activity update

This past week, activity levels at the summit of Kilauea Volcano have remained at background levels. The number of earthquakes located in the summit area has slightly increased (usually less than 10 per day that are large enough to locate) with the largest number located south and west of Halema`uma`u. Widening of the summit caldera, indicating inflation, continues.

Eruptive activity at Pu`u `O`o continues. On clear nights, glow is visible from several vents within the crater. A seismometer at Pu`u` O`o recorded numerous gas-piston-like signals in the past week, though only a few coincided with episodes of flaring glow at the Drainhole vent in Pu`u `O`o crater. Gas-pistons are, essentially, big gas-bubble bursts.

Lava continues to flow through the PKK lava tube from its source on the flank of Pu`u `O`o to the ocean at East Lae`apuki, and through an eastern branch of the PKK tube, called the Campout flow, to the ocean at East Ka`ili`ili. Both locations where lava is entering the ocean are within Hawai`i Volcanoes National Park. There was a breakout from the PKK tube just inland from the sea cliff at East Lae`apuki on Tuesday night, similar to breakouts that occurred there a few weeks ago. The breakout sent lava cascading onto the lava bench, but was stagnant by the following morning.

Access to the sea cliff near the ocean entries is closed, due to significant hazards. The surrounding area, however, is open. If you visit the eruption site, check with the rangers for current updates, and remember to carry lots of water when venturing out onto the flow field.

There were no earthquakes beneath Hawai`i Island reported felt within the past week.

Mauna Loa is not erupting. During the past week, earthquake activity remained low beneath the volcano?s summit (three earthquakes were located). HVO recorded a few minutes of tremor on the morning of September 30. Extension of distances between locations spanning the summit, indicating inflation, continues at slow rates.

Visit our Web site (hvo.wr.usgs.gov) for daily Kilauea eruption updates and nearly real-time Hawai`i earthquake information. skip past bottom navigational bar


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Updated: October 9, 2006 (pnf)