Volcano Watch — Earth has just a handful of long-lived lava lakes

_{(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 Kīlauea 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.

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Volcano Activity Update

On Kīlauea'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 Kīlauea'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).