Hawaii on alert after largest volcano rumbles | Pacific Beat

Hawaii on alert after largest volcano rumbles

Hawaii on alert after largest volcano rumbles

Updated 2 July 2014, 12:42 AEST

Seismologists warn the world's largest volcano, Mauna Loa in Hawaii, is showing signs of a possible eruption in the future.

Wes Thelen, seismic network manager for the United States Geological Survey Hawaiian Volcano Observatory, says there's no impending eruption, but there has been activity lately that's out of the ordinary.

Presenter: Brian Abbott

Speaker: Wes Thelen, seismic network manager for the USGS Hawaiian Volcano Observatory

THELEN: It's been quiet for the last 30 years, 1984 was the last eruption and it has been fairly quiet since then. There's been a couple of seismic swarms, one in 2002 and one in 2004 and 2005, but those were all very deep earthquakes and it appears that there's some increase in seismic activity in sort of the shallower range of the volcano, around ten kilometres or so.

ABBOTT: So this, what you call, swarms is increase in activity. Does it set you a timeline as to when this possible eruption is likely?

THELEN: We don't see any sign of an impending eruption, what we're seeing is earthquakes that are occurring in the same places and they are earthquakes of the same types that we saw before eruptions in 1975 and 1984. So by inference, we're thinking that many of the same processes that were going on before that 1975 and 1984 eruption, are starting to happen again now. That being said, the seismic activity before the 1975 and 1984 eruptions was much larger. There are many, many more earthquakes and they were much bigger than anything that we've seen in the past year or anything since 1984. So we're still at the very early, early stages of potentially an increase in unrest, but at this point, we can't tell exactly when the volcano may erupt. This may go on for several years before anything actually happens at the surface.

ABBOTT: What's the history of eruptions at this volcano? Is it all about ending in a whimper or is it a big bang eruption volcano?

THELEN: The eruptive history of Mauna Loa is quite active in the historical time that we have sort of human recording of eruptions up there and the eruptions always start in the summit area and you'll have an eruption start right at the very top of the volcano and it will produce lava flows and fissures and it will look dramatic.

The interesting or really the scary part is when the magma goes down one of the rift zones and we don't know why magna picks one rift zone over another, but these rift zones are very large cracks, that extend from the summit of the volcano and lava can issue from anywhere along this rift zones and eruptive pattern of Mauna Loa is always that it starts in the summit and then it goes down one of the rift zones and erupts up one of the rift zones. And the problem is is that there are population centres that have grown up in the shadow of these rift zones and so depending on which rift zone the magna runs down and erupts out of, it affects that community that is potentially in the shadow of that rift zone.

ABBOTT: So how many people could be threatened should this volcano decide to erupt in the next couple of years?

THELEN: Well, it really, it's hard to say, because we don't know which rift zone. Certainly the communities of Ocean View are built right on the rift zone. The community of Hilo, which is the county seat of Hawaii is at risk if we have a very large lava flow down the northeast rift of Mauna Loa, but again, since we don't know the volumes coming up, we don't know if the lava flow would make it all the way to Hilo.

For instance, in 1984, in ran towards the town of Hilo, but it never made it there, but there are cases certainly in 1950, where there was a large volume eruption that occurred and towns on the west side of Hawaii were very quickly affected after the rift zone intrusion, after the rift zone eruption began.

ABBOTT: How close to Honolulu, I suppose, is this volcano, it's off on an island of its own, a smaller island?

THELEN: The Island of Hawaii is the southern most and youngest of the Hawaiian chain, so Honolulu is an hour's plane flight away, well, it's three islands away essentially from Mauna Loa, so except for some increase in tourist traffic, the island the Oahu and Honolulu would probably be unaffected from a Mauna Loa event, unless there was winds that brought up some of the gases that were being emitted from the volcano, then there would be some very really affects of the vog but that's all weather-dependent, and we can't tell that ahead of time whether or not they'll be impacted from those volcanic gases or not.

ABBOTT: From what you're saying, can I gather that warnings, such as this, that this Mauna Loa volcano is slowly coming back to life are good for tourists, tourists want to feel that danger by visiting volcanoes when they're bubbling under the ground?

THELEN: The experience from 1984 is that once the eruption began, there was a large flood of tourism that was looking to see that eruption and I don't expect there to be an increase in tourism, associated with just the increased unrest of Mauna Loa. But certainly if there is an eruption, you'll see a dramatic increase in tourism to the big island to simply see the spectacle that is the largest active volcano in the world erupting.

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