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Special to West Hawaii Today

January 31, 2014 - 11:37am

We conclude our Volcano Awareness Month series on the important questions about how Hawaiian volcanoes work with an article on monitoring volcanic activity.

The effects of some of the physical manifestations of volcanic activity, such as ash, vog and earthquakes, are widely experienced by people in Hawaii. Scientists at the U.S. Geological Survey’s Hawaiian Volcano Observatory use monitoring tools to measure and analyze these byproducts of volcanic activity and their relation to the activity itself — such as the extent of lava flows, deformation of ground surface, and the distribution and effects of earthquakes.

Perhaps the most important aspects of volcanic activity that should be monitored involve a volcano’s magma budget — the balance between the amount of magma erupted from the volcano versus the amount supplied to it.

There are various methods for measuring eruption rate, but all have limitations. For example, the amount of gas emitted from a vent is proportional to the amount of lava erupted from that vent, but this relation has not been reliable since the onset of Kilauea’s summit eruption in 2008, when the style of gas emissions from the volcano changed.

Quantifying flows through lava tubes can provide an eruption rate, but this requires the flow of lava through a single tube in an easily observed area — a condition that has not existed for several years. Thermal measurements can also indicate eruption rate but require cloud-free satellite images and surface flows, as opposed to tube-fed lava flowing directly into the ocean, both of which are rare conditions at Kilauea.

Satellite measurements of surface topography offer a new method of measuring lava eruption rate. A pair of satellites orbiting Earth since 2011 can generate a map of elevations approximately every 11 days. By comparing elevations acquired from successive satellite overpasses, topographic changes caused by lava flow activity can be measured over time and yield the lava eruption rate.

The satellite topographic technique will work, however, only when lava-flow activity is confined to land, as is now occurring at Kilauea. It also produces measurements only when the satellite passes overhead, as opposed to when the scientists monitoring the volcano need the data. Nevertheless, this method of measuring eruption rates complements existing methods and confirms the value of using satellite data to monitor volcanoes.

In addition to measuring what comes out of a volcano, it is also important to assess what goes in. The supply of magma to a volcano is the most fundamental control on eruptive activity. But how can a process occurring deep underground and out of sight be investigated? Data from Kilauea indicate that the emission rate of carbon dioxide may provide a solution.

Between 2003 and 2007, a surge in magma supply to Kilauea resulted in numerous changes in eruptive activity. This surge was preceded by a near-doubling of CO2 emissions from Kilauea’s summit — a sign that an increased amount of magma was rising beneath the volcano. Unfortunately, the CO2 emission rate is difficult to measure, because detecting the gas requires special conditions at Kilauea’s summit. Since carbon dioxide is present in Earth’s atmosphere, identifying volcanic CO2 from background atmospheric CO2 is not easy.

New technology may help detect volcanic CO2 emissions, and volcanologists plan to use Kilauea as a testing ground for these techniques in the coming years. Inferring the rate of magma supply to a volcano based on CO2 emissions may become commonplace in the near future. Combined with improved measurements of eruption rate, routine monitoring of the magma budget of a volcano may finally be realized.

This concludes our annual Volcano Awareness Month series of Volcano Watch articles. For more information on the big questions related to Hawaiian volcanoes, you may attend an HVO talk on the subject in Hawaii Volcanoes National Park on Feb. 4. Details are posted at

Kilauea activity update

A lava lake within Halemaumau produced nighttime glow visible via HVO’s webcam during the past week. The lava level fluctuated with two deflation-inflation events and ranged from 140 to 190 feet below the rim of the overlook vent.

On Kilauea’s east rift zone, the Kahaualea 2 flow continued to be active northeast of Puu Oo. After the flow front stalled more than a week ago, 4.8 miles northeast of Puu Oo, the flow reactivated late last week. This new activity, however, is back from the stalled flow front and is about 3.5 miles northeast of Puu Oo. Webcam images indicate that small forest fires have resumed.

There were no earthquakes reported felt on Hawaii Island in the past week.

Visit for Volcano Awareness Month events and current Kilauea, Mauna Loa and Hualalai activity updates, recent volcano photos, recent earthquakes and more; call 967-8862 for a Kilauea summary; email questions to

Volcano Watch is a weekly article and activity update written by scientists at the U.S. Geological Survey’s Hawaiian Volcano Observatory.