Geology provides the foundation for volcano monitoring

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In recognition of Volcano Awareness Month (January 2011), this column is exploring the different techniques used by Hawaiian Volcano Observatory (HVO) scientists to monitor Hawai‘i's volcanoes. Last week, we began with a discussion of potential-field geophysics. This week, we will focus on geologic monitoring of volcanoes.

Geology provides the foundation for volcano monitoring...

An HVO geologist uses GPS to map and track the progress of an ‘A‘ā lava flow in Royal Gardens subdivision in 2008. USGS photo.

(Public domain.)

Geologic studies are the foundation of all volcano monitoring efforts. The first step in any geologic study of an active volcano is to map deposits produced by previous eruptions, such as lava flows and ash deposits, and volcanic structures, such as faults, calderas, and craters. With this information, volcanologists gain a better understanding of the types of eruptions that may occur from a given volcano. During future times of volcanic unrest at that volcano, this knowledge can be used to guide forecasts of the most likely style of eruption, the size of the eruption, and the area that might be impacted.

For example, prior to the June 1991 eruption of Pinatubo, which was, at the time, a little-known volcano in the Philippines, geologists identified large pyroclastic flow and lahar deposits that reached many tens of kilometers (miles) from the volcano. Based on their mapping, the potential for a very large eruption was recognized, and evacuations were planned accordingly. As a result, many thousands of lives were saved when the volcano erupted.

Geologic observations are critical to understanding the nature and likely course of eruptive activity. Over the last year, HVO geologists have spent many days in the Kalapana area mapping the active lava flow field. The purpose of their work is to track the progress of the lava flows and assess their likely future paths. This information is then communicated to Hawai‘i County Civil Defense, which can take necessary actions to protect lives and property. Photos, maps, and text updates from these observations are posted as part of HVO's daily activity update.

Geologists also rely on cameras to record volcanic activity. HVO maintains a network of Webcams that are linked to the Observatory via radio signal and provide regular images of Kīlauea's summit and east rift zone and of Mauna Loa's summit. These cameras afford up-to-the-minute views without the need for helicopter flights or personnel on the ground. You can see these Webcam images at http://hvo.wr.usgs.gov/cams.

In addition, time-lapse cameras are deployed at numerous locations around Kīlauea. Images from these stations have provided views of lava flowing through tubes, the episodic rise and fall of lava within both the summit and Pu‘u ‘Ō‘ō vents, lava fountaining on the flanks of Pu‘u ‘Ō‘ō, and many other processes. A selection of time-lapse movies from remote cameras is available on HVO's Web site at http://hvo.wr.usgs.gov/gallery/kilauea/volcanomovies.

Recently, HVO has also begun using thermal cameras to track lava flow activity. Thermal cameras have the great advantage of being able to "see" through much of the steam and gas emissions that obscure views by traditional cameras—an especially important feature for monitoring lava activity in eruptive vents at the summit and at Pu‘u ‘Ō‘ō.

In the past two decades, satellite monitoring, or remote sensing, has provided a means of visual and thermal monitoring of volcanoes without requiring geologists on the ground. For instance, researchers at the University of Hawai‘i have developed a system that automatically detects thermal anomalies at volcanoes, which often provides the first indication of eruption for many locations that are not monitored by ground-based equipment.

Geology is clearly the cornerstone of any volcano monitoring program. Tune in next week, as our series on volcano monitoring methods continues with a discussion of gas geochemistry.

Until then, you're invited to attend one or more of this week's Volcano Awareness Month activities: an update on Kīlauea's summit eruption in Hawai‘i Volcanoes National Park Visitor Center on January 11, a presentation about who watches out for you during an eruption at the University of Hawai‘i at Hilo on January 14, and daily National Park programs. Details about these activities are available at http://hvo.wr.usgs.gov or by calling 808-967-8844.

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Volcano Activity Update

Lava flows have been active on the pali and coastal plain west of Kalapana over the past week. The easternmost of the active flow lobes crossed the end of Highway 130 early in the week and continues to advance slowly to the southeast. The western lobe crossed the coastal flats near Kapa‘ahu and reached the ocean on Thursday (January 6). The new ocean entry is about 2 km (1.25 mi) southwest of the end of Highway 130. At Pu‘u ‘Ō‘ō, lava flows have been spreading across the northeastern part of the crater floor. They are erupting from a spatter cone in the north-central part of the crater.

At Kīlauea's summit, the circulating lava lake in the collapse pit deep within the floor of Halema‘uma‘u Crater has been visible via Webcam throughout the past week. The circulation pattern was interrupted sporadically by abrupt increases in the height of the lava surface. These periods of high lava level have been short-lived, lasting from 10 minutes up to several hours, and each ended with a sudden drop of the lava surface back to its previous level. Volcanic gas emissions remain elevated, resulting in high concentrations of sulfur dioxide downwind.

One earthquake beneath Hawai‘i Island was reported felt during the past week. A magnitude-2.1 micro-earthquake occurred at 4:08 p.m. HST on Wednesday, January 5, 2011, and was located 7 km (5 mi) east-northeast of Honauanau at a depth of 7 km (4 mi).