Friday, May 4, 2018

Eruption Begins in the Big Island's Puna District

Erupting vent of Pu'u O'o and the East Rift in 2009
The people of Hawai'i have a lot on their hands at the moment. A few months ago, someone pushed the wrong button, and the inhabitants thought for 45 minutes that they would be incinerated by North Korean bombs. Just two weeks ago, the island of Kaua'i was hit by an epic record-setting storm that dropped feet of rain and caused widespread flood damage that they are only beginning to clean up. And then tonight comes news that a new eruption is taking place on the Big Island.
Developments in the Puna District on the East Rift Zone of Kilauea (2009)

The words "volcanic eruption on the Big Island" aren't normally an extraordinary story. Kilauea has been erupting continuously since 1983, and lava flows have been emanating from Pu'u O'o in the East Rift Zone. Since 2008 the summit caldera of Kilauea has been erupting as well. The summit flow actually made news last week when the lava pit filled and overflowed into the floor of the caldera. But today's news is a bit more ominous.

Most of the activity in recent years has been in isolated parts of Hawai'i Volcanoes National Park, and along the coast where the lava has been flowing into the sea without causing major damage (but to be clear, hundreds of homes in the Kalapana District were destroyed in the early phases of the Kilauea eruption). But the Puna District lies miles east of Pu'u O'o vent, and lava flows there are relatively uncommon. There were extensive flows in 1790, 1840, 1955 and 1960. A flow in 2014 briefly threatened homes in Pahoa (see the map below). In the years since these eruptions, a thick rainforest has grown over the lava flows, hiding the evidence of their destruction. And people moved in. Housing developments proliferated on and near the older lava flows.

This week, the summit cone of Pu'o O'o collapsed and sent an unusual pink cloud of ash rising over the Puna District. Lava drained from the molten lake at the cone and began intruding underground in  the cracks and fissures of the East Rift Zone. Dozens of earthquakes heralded the movement of the magma, and cracks appeared here and there on roads in the region. And word comes tonight that a rift zone eruption has begun very close to the Leilani Estates. Evacuations have begun, and we now must wait to see how events unfold. I'm hoping that damage will be minimal.
Pu'u O'o on May 3, 2018, courtesy of the U.S. Geological Survey

I've enjoyed my visits to the Puna District. One of the most fascinating sights are the tree molds from the 1790 lava flow at Lava Trees State Park. When the lava encroached into the rainforest, it tended to freeze solid around the tree trunks, and then the lava flow subsided somewhat as it continued down the slope. The trees burned of course, but the lava maintained the shape of the trunks as empty molds.

The native Hawaiian people saw these monuments as frozen beings. Do you see the face in the mold below?
On a field trip in 2004 we spent several of our Hawaii hours in...a power plant! It's significant because it is a geothermal plant that uses the hot water emanating from magma chambers deep in the crust beneath the 1790 lava flow to provide 20% of the electrical needs of the Big Island. It is now threatened by the current activity.
The Hawaiian Islands owe their very existence to the hot magmas emanating from the Earth's mantle, but living on the Big Island entails risks related to the constant volcanic activity. Pele's whims can never be taken for granted. Active lava flows are a spectacular draw for tourists (including me whenever possible), but they can threaten those who live there.
Lava flows on the flanks of Pu'u O'o in 2009
It's been a tough couple of months for the people of Hawai'i. My heart goes out to them.

Updates from the United States Geological Survey and the Hawai'i Volcanoes Observatory can be found at: https://volcanoes.usgs.gov/volcanoes/kilauea/status.html. Emergency updates from the County of Hawai'i can be found at http://www.hawaiicounty.gov/active-alerts/.
Ocean entry of lava flows from Pu'u O'o in 2009