Volcano Watch

Volcanic hazards come in many forms. The most common hazards for Hawai‘i include earthquakes, lava flows, and wide-ranging vog. What is the definition of hazard?

Merriam-Webster defines “hazard” as a source of danger. Other definitions from dictionary.com include 1) an unavoidable danger or risk, 2) something causing unavoidable danger, peril, risk, or difficulty. In the last two definitions, the term “risk” is introduced. What is “risk”?

“Risk” is defined by dictionary.com as “exposure to the chance of injury or loss; a hazard or dangerous chance.” In volcanology, risk has been defined as the impact (damage) that an event would have on humans within the area affected. This extends to person(s), property, or anything of economic value.

Risk can be defined as the mathematical product of hazard, vulnerability, value, and likelihood (assuming that these concepts can be expressed in numbers).

Everyone on the Island of Hawai`i should be aware of the fact that there are at least three active volcanoes and that lava flows present a significant hazard. The most persistent hazard is vog. Yet, the most damaging hazard is a large earthquake, such as the 2006 Kiholo Bay earthquake that impacted communities as far away as O`ahu.

Simply defined, “vulnerability” is the percentage of value likely to be lost if a hazardous event occurred. If lava contacts your wooden house, it will burn; the house is 100 percent vulnerable. Many houses survived the 2006 Kiholo Bay earthquake with minor damage thanks to improved building codes; therefore, the vulnerability was a small fraction of the cost of a new home.

“Value” is defined explicitly as the dollar amount of life and (or) property that is lost by a hazardous event. Some things are easily tabulated because we see and use them in everyday life—homes lost, roads buried, electrical poles burnt, TV and Internet cables damaged, etc.— and are components of fixed infrastructure; they are relatively easy to quantify.

We would be remiss in future risk assessment if we ignored the loss of productive capacity or the economic loss due to a hazardous event, where businesses and people are unable to earn money.

For example, what would happen if a flow from Mauna Loa advanced down the flank of the volcano and entered the ocean? It is plausible that no homes would be impacted by such a flow, yet highways would be severed, commerce would be impeded, workers could not get to their jobs because travel would be disrupted. The loss of future earnings is harder to assess and has wide-ranging repercussions.

“Likelihood” is often incorporated into the term “hazard” in the risk equation. It is often expressed in terms of probability. Probability estimation is not an easy task and, for lava flow hazards, is based on lava flow ages. To do the best job, we need to determine the recurrence interval (RI) for all lava flows, and this requires access to all lands impacted by lava.

The RI is the average time between past lava flows. For example, in the 167 years since 1843, Mauna Loa has erupted 33 times; 167 years divided by 33 eruptions is about 5 years between lava flows.

Probability and recurrence interval vary inversely. The shorter the RI, the larger the probability that a lava flow will occur in a given period. In our example, the probability of a Mauna Loa eruption occurring in any one year is about 1/5 or 20 percent. Probability can be a difficult concept for many people to grasp. Geologic hazards are generally considered to be random events; there is an equal chance that it will occur in any given year. Passage of a significant amount of time since the last hazardous event does not necessarily mean that there is a greater chance of another one occurring.

Geologic hazards are a reality of living on the flanks of active volcanoes. It is important to know what those hazards are. Risks can be reduced by being prepared and planning for hazardous events. Furthermore, land use planning is the most effective tool for mitigating lava flow hazards. All in all, living on the flanks of volcanoes can be a risky business.

Kilauea Activity Update

Over the past week, activity on the east rift zone flow field remains focused on the construction of low shields. This activity was located well above the Pulama pali, over the breakout point of the Quarry flow. Weak activity continues along the Quarry flow itself from the top of the pali to the coastal plain. In addition to that lava erupting and flowing through the TEB and Quarry flow tube systems, lava is also erupting from two vents within Pu`u `O`o. These vents are slowly filling Pu`u `O`o’s crater, and the Webcam on Pu`u `O`o has been providing spectacular views both day and night.

At Kilauea’s summit, a circulating lava pond deep in the collapse pit within the floor of Halema`uma`u Crater was visible via the Webcam throughout the past week. The baseline lava level continues to rise slowly and was punctuated a few times by short-lived lava-level increases that brought the lava surface to its highest level yet recorded. Volcanic gas emissions remain elevated, resulting in high concentrations of sulfur dioxide downwind.

No earthquakes beneath Hawai`i Island were reported felt during the past week.

Visit the HVO Web site for detailed Kilauea and Mauna Loa activity updates, recent volcano photos, recent earthquakes, and more; call (808) 967-8862 for a Kilauea summary; email questions to askHVO@usgs.gov.

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

What volcanic locale do the following characteristics describe? (1) A persistent lava pond within a deep pit crater, just below a popular visitor overlook in a national park, (2) Small explosions that have thrown debris over a nearby visitor parking lot, (3) A continuous gas plume, producing choking vog that affects downwind communities, (4) The sacred home of a fearsome female deity.

To most Volcano Watch readers, these descriptions would rouse thoughts of Halema`uma`u Crater, at Kilauea’s summit. Its ongoing eruption, now entering its third year, exhibits all the characteristics above.

But, remarkably, these traits also describe Masaya volcano, a broad basaltic shield just outside the city of Managua in Nicaragua. It is frequently active, with Spaniards first documenting its activity in 1525. Some Spaniards believed it was the mouth of hell, while others tried to extract the gold they thought was within the active vent. To indigenous people, Masaya was the home of Chalchiutlicue, the water deity, who was an old and wise sorceress with sharp fangs.

In recent decades, a deep pit crater at Masaya has hosted persistent lava activity. At times, there is a lava pond, and, at other times, the floor of the crater consists of rubble with small incandescent openings. Visitors can see the vent from the overlook on the crater rim. In April 2001, a small explosion scattered rocks across the visitor parking lot, just beside the overlook, damaging cars and buses. Tourists at the overlook sought refuge in their vehicles or fled on foot; several sustained injuries from flying debris. Despite the danger, Masaya continues to be a popular visitor destination in Nicaragua.

Persistent lava lakes and lava ponds exist at several other volcanoes. Mount Erebus, on Ross Island in Antarctica, has hosted a small lava lake since at least 1972, and possibly as far back as 1841. Mount Erebus’ lava lake is notable, in part, because of the frequent small explosions in which large gas bubbles can be seen rising to the surface and bursting in spectacular fashion.

Two long-lived lava lakes are situated in Africa. Erta Ale volcano, in a remote part of Ethiopia, has hosted a lava lake since at least 1967. The lava surface consists of slowly migrating crustal plates, with upwelling in one portion of the lake and sinking in another. Mount Nyiragongo, in the Democratic Republic of the Congo, is a large stratovolcano that has hosted a lava lake since at least the 1950s. The lava lake has drained several times through the volcano’s flank, producing fast-moving flows that have entered the city of Goma with deadly results.

How can lava lakes exist for decades? All persistent lava lakes share a fundamental process—called magmatic convection—that enables them to remain fluid. It begins with gas-rich magma rising from depth. As the magma approaches the surface, the gases bubble out and escape. The magma at the top of the column, now degassed and somewhat cooled, is slightly denser and sinks back down the conduit. This cycling of mass and heat sustains an open, active vent—a process now underway at Halema`uma`u.

Persistent lava lakes are invaluable to scientists because they offer a “natural laboratory” for volcanic processes. The continuous activity provides ample time to observe magmatic convection, crustal foundering, degassing, and spattering behaviors. Changes in activity can be observed and used as keys to understanding the deeper magmatic system.

What can we learn about Halema`uma`u from these other lava lakes? Whereas eruptions are relatively brief at most volcanoes on Earth, persistent lava lakes demonstrate that some volcanoes can maintain continuous activity for decades or more. We know that Halema`uma`u’s lava lake persisted through much of the 1800s and early 1900s, so Halema`uma`u is essentially already a part of this exclusive group.

The question is whether Halema`uma`u’s current activity will continue sufficiently long that it can renew its membership in the persistent lava lake club. Only time will tell, and HVO will continue to watch and learn from this fascinating eruption.

Kilauea activity update

On Kilauea’s east rift zone, small breakouts were active well above the pali, about 1 km (0.6 mile) above Royal Gardens subdivision, through the week. There are no active flows on the face of the pali, on the coastal plain, or in the National Park.

At Kilauea’s summit, a spattering and roiling lava surface deep within the collapse pit inset within the floor of Halema`uma`u Crater was occasionally visible via Webcam during the past week. 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-2.9 earthquake occurred at 1:11 a.m. on Wednesday, March 24, 2010, H.s.t., and was located 15 km (9 miles) west of Pahala, at a depth of 3 km (2 miles).

Visit the HVO Web site for detailed Kilauea and Mauna Loa activity updates, recent volcano photos, recent earthquakes, and more; call (808) 967-8862 for a Kilauea summary; email questions to askHVO@usgs.gov.

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

Lava in Kîlauea’s summit vent creates a nighttime glow that can be safely observed from the Jaggar Museum overlook in Hawai‘i Volcanoes National Park or on the HVO Webcam. Inset image shows the lava surface, which was moving from top center to lower left at the time it was taken.

The Hawaiian Volcano Observatory website was recently revamped to make access to our increasing number of Webcams easier for viewers and the HVO staff who post Webcam images. All HVO Webcams are now linked through a single menu.

The menu lists our five Webcams showing Moku`aweoweo, Mauna Loa summit caldera, the TEB vent and lava tube system on Kilauea’s east rift zone, Pu`u `O`o crater, and two views of the Halema`uma`u vent – one from HVO and another from the rim of Halema`uma`u crater immediately above the new vent.

Webcams allow us to make critical measurements with relatively little risk. The Webcams can work in rain, wind, very high concentrations of sulfur dioxide, and even moderate amounts of ash blasted from the vent. They can be in areas where access is restricted for safety reasons. Webcams can be where people should not.

Two of our Webcams have shown active lava in recent days. On Tuesday night, the TEB Webcam caught active flows near the top of the abandoned Royal Gardens subdivision. As an added treat, the Webcam also caught lights from a cruise ship passing the Kalapana shoreline in the late evening getting good views of the active flows and the Waikupanaha ocean entry.

The Webcams that chronicle developments below the floor of Halema`uma`u Crater have recorded lots of glow since early May. In fact, the recent glow has been the brightest since October 2008. The brightness of the glow is due to molten lava circulating in a narrow conduit about 100 m below the crater floor and about 180 m below the crater rim.

The Webcam located on the rim of Halema`uma`u was recently repositioned to look directly into the vent for views of the circulating lava when clear enough. The wispiness of the gas plume and the relative shallowness of the molten lava have allowed some good views recently. The vent is masked by sunlit fume during the day and is overexposed at night so the best times to look at Webcam views of lava are at dusk and dawn.

The unwavering Webcam views will allow us to better monitor the rise and fall of the lava within the vent. HVO geologists have also recorded video of the lava surface that shows some fascinating movements. The lava emerges from the right side of the Webcam view and flows left across the opening. The flowing lava surface looks chaotic with lots of splashing and bursting bubbles —activity that produces the tephra that is carried aloft by the hot, rising gas and deposited on the rim.

Two recent Volcano Watches have discussed reasons for lava circulation using a lava lamp analogy. Magma must be convecting with the conduit, like the “goo” in a lava lamp, bringing hot, bubble-rich lava to the surface while allowing cooler, bubble-poor lava to sink.

Looking at lava within the Halema`uma`u vent conduit is like watching a lava lamp from above through a hole in the top, all the goo colored orange, and blobs being gas bubbles that burst when they get to the top.

Views from the Halema`uma`u Webcam should allow us to test our ideas about what precedes brown plumes and explosive eruptions. Do rocks fall from vent walls into the molten circulating lava trigger a vigorous gas release which could carry even more spatter and rock dust out of the vent. Or are the brown plumes and more energetic explosive eruptions initiated by a big slug of gas coming up the conduit.

For safety reasons, Hawai`i Volcanoes National Park restricts access to the entire caldera including Crater Rim Drive from Jaggar Museum south to the Chain of Craters Road intersection. Thanks to the HVO Webcams, we can all see what’s happening from much safer vantage points.

Kilauea Activity Update

A deflation/inflation (DI) event at the summit of Kilauea last weekend disrupted the supply of lava through the tube system and caused the Waikupanaha and Kupapa`u ocean entries to shut down. Both entries had resumed by mid-week, accompanied by breakouts near the top of Royal Gardens subdivision and just inland from Kupapa`u.

At Kilauea’s summit, the vent within Halema`uma`u Crater continues to emit elevated amounts of sulfur dioxide gas, resulting in high concentrations of sulfur dioxide downwind. Vigorously upwelling lava within the vent below the crater floor produced bright glow at night, loud gas-rushing noises, and the emission of juvenile ash during the past week.

One earthquake beneath Hawai`i Island was reported felt this past week. A magnitude-3.4 earthquake occurred at 3:55 p.m., H.s.t, on Saturday, May 30, 2009, and was located 9 km (6 miles) southwest of Kilauea Summit at a depth of 26 km (16 miles).

Visit the HVO website for detailed Kilauea and Mauna Loa activity updates, recent volcano photos, recent earthquakes, and more; call (808) 967-8862 for a Kilauea activity summary; email questions to askHVO@usgs.gov. Volcano Watch is a weekly article and activity update written by scientists at the U.S. Geological Survey’s Hawaiian Volcano Observatory.