Volcano Watch — Monitoring lava flows with boots on the ground and eyes in the sky

Volcanology is fundamentally an observational science. To better understand how volcanoes work, scientists must examine volcanic eruptions and their deposits. Field observations are, therefore, at the core of HVO's response to lava flow activity on the Island of Hawai‘i.

In that regard, little has changed since lava flows inundated Kalapana in 1990. As flows advanced toward, and ultimately through, that community, HVO geologists were on the ground, making detailed maps that were used to alert Civil Defense officials and local residents of the potential lava-flow hazards. While the basic nature of geologic observations has not changed, the tools we use today are much different than those used 25 years ago.

In 1990, HVO geologists mapped lava flows by hand, on the ground and from the air, using recent aerial photos of the area for orientation. Lava flow outlines were sketched onto an acetate sheet overlain on the aerial photo. As lava covered more and more of the community, it became increasingly difficult to determine precise flow locations due to the lack of identifiable landmarks. In some cases, downed power lines were the only indication of where roads had been! Back in the office, the flow outlines from the aerial photos were transferred to a paper topographic map for copying and distribution.

Today, lava flows are mapped using space-based methods. As described in last week's Volcano Watch, timely satellite data can be used to track flow progress, especially when crews are not able to get to the field. When scientists are able to observe the flow directly, either on the ground or by helicopter, they map the flow boundaries using the Global Positioning System (GPS).

Although GPS was available in 1990, the instrumentation for recording positions was bulky and expensive, and data were not especially accurate because the U.S. military intentionally degraded the signal. This scrambling, called "selective availability," was turned off in 2000, allowing GPS users around the world access to the same accuracy as the military, down to a few meters (yards). Technological developments also improved the quality of GPS receivers, resulting in the compact handheld units that are so common today and easily used in the field.

Using handheld GPS units, HVO geologists can now quickly map flows via helicopter or by walking around flow margins. Upon returning to HVO, they download the GPS data and plot the flow margins on a map using Geographic Information System (GIS) software. Other map layers, like roads and towns, are added to the plots to produce the maps published on HVO's website (http://hvo.wr.usgs.gov/maps). These maps form the basis for much of HVO's monitoring of the June 27th lava flow.

In addition to GPS data, geologists track flow activity using both regular and thermal cameras, capturing images from the ground and from the air (both types of images are posted on HVO's website, http://hvo.wr.usgs.gov/multimedia/index.php, after crews return from the field). HVO scientists recently developed the ability to create a mosaic of thermal images, which provide high-resolution views of active lava breakouts over the entire flow field.

Over the past 25 years, technological advances have enabled more accurate and timely tracking of lava flows from the ground, air, and space, as well as rapid distribution of that information via the Internet. Although the fundamental observations made by HVO geologists remain much the same, the manner in which data are collected has greatly improved.

Next week, we conclude the 2015 Volcano Awareness Month series of Volcano Watch articles with an introduction to a new HVO staff scientist who specializes in studying ground deformation using a variety of tools, including GPS! Between now and then, we hope to see you at our final two Volcano Awareness Month talks offered in Hawai‘i Volcanoes National Park on Jan. 27 and in Kona on Jan. 28. For more information about these talks, please visit http://hvo.wr.usgs.gov, email askHVO@usgs.gov, or call 808-967-8844.

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Volcano Activity Update

Kīlauea's East Rift Zone lava flow remained active with breakouts scattered across the leading 3 km (2 mi) of the flow, in the area near the abandoned True/Mid-Pacific geothermal well site, and farther upslope near Pu‘u ‘Ō‘ō. The leading tip of the flow remains active but has been sluggish for much of the past week, and was 600 meters (0.4 miles) upslope of Highway 130 on Thursday, January 22.

The summit lava lake level was relatively steady over the past week, and was about 45 meters (150 ft) below the rim of the Overlook crater.

There were two earthquakes in the past week reported felt on the Island of Hawai‘i. On Monday, January 19, 2015, at 12:30 a.m., HST, a magnitude-3.5 earthquake occurred and was located 5.5 km (3.4 mi) south of Honoka‘a at a depth of 13.6 km (8.4 mi). On Thursday, January 22, at 7:51 a.m., a magnitude-2.7 earthquake occurred and was located 6.5 km (4.0 mi) northwest of Nā‘ālehu at a depth of 8.1 km (5.0 mi).