Weekly Erution Update: Kilauea Volcano, Big Island of Hawaii

Reprinted from here.

HVO Hot Shots See the Heat at Kilauea

Visible and thermal images of Halema`uma`u Crater before and after the emergence of the new vent and its first explosion.

If you keep an eye on the Kilauea update images posted on the HVO website, you may have noticed over the last few months that we have occasionally shown thermal images of the ongoing activity. The images typically have a background of black and blue, representing lower temperatures, with bright areas of red and orange showing higher temperature areas, such as active lava.

So, how do we collect these images, and what can they tell us about how the volcano is working?

We use a handheld thermal camera, which collects radiation in the infrared range of the electromagnetic spectrum. The size of the unit - only slightly larger than a typical camcorder - makes it easy to use from a helicopter or stow in our backpacks if we have to trudge off on a hike.

Most of the images are taken during our routine helicopter overflights to monitor the current east rift zone activity. Our interpretation is improved by obtaining corresponding photographs from a conventional camera to compare to the thermal images. To achieve this, we make sure the geologist operating the thermal camera sits on the same side of the helicopter as the geologist taking photographs. The thermal camera is also being used to monitor activity at the new vent in Halema`uma`u Crater. Each day, we take images of the vent from the Jaggar Museum overlook.

But how exactly can thermal cameras help to monitor the volcano? It's been said that the most important variable at volcanoes is temperature. In a rough sense, the level of surface activity is directly tied to temperature. For instance, a lava flow stops once its temperature drops enough for the lava to solidify.

Let's look at ongoing thermal camera uses at Kilauea. On our overflights of the flow field, we use the camera to aid in identifying the extent of active, or recently active, flows. Sometimes recently cooled flows are hard to identify with the naked eye, because they appear as black as surrounding flows. But in the thermal images, these still-warm flows stand out like day and night.

Another application is tracking lava tubes, which may be difficult to trace with the naked eye, because they lie below a surface of solidified lava. The lava surface overlying the tube, however, is heated up slightly by the flowing lava. Lava is a poor conductor of heat, so this temperature difference may be subtle. When scaled properly, the images show a clear line of higher temperatures that precisely track the path of the tube.

Just recently, the thermal camera proved essential for characterizing the new vent on Pu`u `O`o's east wall. With the naked eye, we could see a new plume jetting from the rim, but we couldn't see through the thick fume inside the crater to judge the precise location or extent of the new gas source. Because the thermal camera measures longer wavelengths than the human eye, it was able to clearly "see" through the fume and identify the new vent.

At Halema`uma`u, our daily thermal images over the last few months have shown an interesting long-term trend at the new vent. Vent temperatures rose in late March following the March 19 explosion and peaked in early April. Since then, the values have been gradually decreasing. The cause of this long-term decrease is not yet clear, but it could be due to a crusting-over of lava in the conduit or to a steady lowering of the lava level.

Thermal cameras are becoming a more common tool for volcano monitoring around the world, aided, in large part, by technological advances over the last decade that have made the cameras much smaller and lighter. Because the cameras are precision calibrated and manufactured by just a few companies worldwide, you unfortunately can't pick one up from your local department store. Not surprisingly, this means their cost is more than that of a standard camcorder. For us, they are worth the price, because they provide a new set of "eyes" and greatly enhance our monitoring of volcanic activity and hazards.

Activity update

Kilauea Volcano continues to be active. A vent in Halema`uma`u Crater is erupting elevated amounts of sulfur dioxide gas and very small amounts of ash. Resulting high concentrations of sulfur dioxide in downwind air have closed the south part of Kilauea caldera and produced occasional air quality alerts in more distant areas, such as Pahala and communities adjacent to Hawai`i Volcanoes National Park during kona wind periods.

Pu`u `O`o continues to produce sulfur dioxide at even higher rates than the vent in Halema`uma`u Crater. Trade winds tend to pool these emissions along the West Hawai`i coast. Kona winds blow these emissions into communities to the north, such as Mountain View, Volcano, and Hilo. Our Frequently Asked Questions webpage at hvo.wr.usgs.gov provides lots of information about sulfur dioxide, vog, and ash from Kilauea.

The new gas vent observed on May 23 inside Pu`u `O`o has remained active, with no observed change. Lava from the 2007 Thanksgiving Eve Breakout (TEB) flow, erupting from fissure D of the July 21 eruption, continues to flow through what remains of Royal Gardens and across the coastal plain to the ocean in well-established lava tubes. Over the past week, the Waikupanaha ocean entry has remained active, with small explosions and a vigorous plume.

Be aware that lava deltas could collapse at any time, potentially generating large explosions. This may be especially true during times of rapidly changing lava supply conditions, as have been seen lately. Do not venture onto the lava deltas. Even the intervening beaches are susceptible to large waves generated during delta collapse; avoid these beaches. In addition, steam plumes rising from ocean entries are highly acidic and laced with glass particles. Check Civil Defense Web site (http://www.lavainfo.us) or call 961-8093 for viewing hours.

Mauna Loa is not erupting. No earthquakes were located beneath the summit. Continuing extension between locations spanning the summit indicates slow inflation of the volcano.

Three earthquakes beneath Hawai`i Island were reported felt within the past week. A magnitude-2.4 earthquake occurred at 6:12 a.m., H.s.t., on Saturday, June 21, 2008, and was located 2 km (1 mile) southwest of Kilauea summit at a depth of 2 km (1 mile). A magnitude-3.1 earthquake occurred at 5:16 p.m. on Sunday, June 22, and was located 1 km (1 mile) southeast of Pahala at a depth of 14 km (8 miles). A magnitude-3.3 earthquake occurred at 0:51 a.m. on Tuesday, June 26, and was located 10 km (6 miles) west of Pahala at a depth of 7 km (4 miles).

Visit our Web site (http://hvo.wr.usgs.gov) for daily Kilauea eruption updates, a summary of volcanic events over the past year, and nearly real-time Hawai`i earthquake information. Kilauea daily update summaries are also available by phone at (808) 967-8862. Questions can be emailed to askHVO@usgs.gov.

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