The eruption of Kīlauea that began on 3 May has caused sudden and dramatic changes to the geography of Hawai‘i Island. The summit crater is now larger, and lava flowing into the ocean more than 32 kilometers away is creating new shorelines.
Throughout the disaster, mapping the changes has been critical, with public safety officials depending upon scientists at the Hawaiian Volcanoes Observatory (HVO) to give them the latest information about what the lava was doing and where it might go next. “It’s a resource that we absolutely need, to see the extent of the flow, so that we can plan a proper response,” said Daryn Arai, deputy planning director for the county of Hawai‘i.
But keeping maps up to date hasn’t been easy. With an eruption that’s often dangerous to observe up close, volcanologists have used drones, satellites, sensors, and a suite of other tools to monitor a landscape that sometimes changes by the hour as lava pools and piles up.
Here are four ways that Kīlauea is changing the geography of Hawai‘i Island.
1. Flows Are Creating a New Topography
Ask any geoscience student: No field study of a landform is complete without a look at a topo map. But when lava gushes and oozes, those baseline maps quickly become obsolete.
So during this eruption, scientists are constantly making new maps. As lava has flowed downhill from fissures on Kīlauea’s eastern flank, scientists used satellite data combined with thermal images and photographs taken on helicopter flights to map the flow’s boundaries daily.
“If the flow is moving especially fast, we might do a second one every day,” said Mike Zoeller, a geologist with the Center for the Study of Active Volcanoes at the University of Hawai‘i at Hilo, who works in partnership with HVO.
Tracking the flow’s margins gives only part of the story: Researchers also need to track how fresh lava is changing the area’s topography.
“It essentially adds elevation to the land within its flow boundaries,” Zoeller said. “That new topography affects later flows.”
The U.S. Geological Survey (USGS) worked with the private geospatial data firm Quantum Spatial to conduct high-resolution lidar surveys of the flow and surrounding areas, flying 11 missions over 6 days in June. Comparing new lidar surveys to maps from before the eruption gives an indication of the thickness of fresh lava flows. HVO scientists have also made spot checks of flow thickness from ground level, Zoeller said.
The lidar data and their ground truths have allowed HVO scientists to determine that the flow is as much as 20 meters thick in some places. They also found that a spatter cone forming around fissure 8, the primary source of lava for the past several weeks, is 50 meters high and growing.
Measuring the lava’s thickness helps scientists determine the total output of the eruption, estimated now at well past 250 million cubic meters. And looking at how those volumes change over time can help them predict whether an eruption is ramping up or starting to slow down—although it’s too soon to know this about Kīlauea, Zoeller said. “We don’t have enough data points yet.”
2. Lava Is Redrawing the Shoreline
One month after the eruption started, a flow from fissure 8 reached the ocean at Kapoho Bay, a secluded cove with a rocky shoreline and clear, calm blue water surrounded by a gated community. Within 3 days, lava had completely filled the bay, creating a lava “delta” that extended more than 1.6 kilometers offshore.
By comparing the flow’s boundaries with bathymetric maps of the ocean floor created by the University of Hawai‘i, scientists know the flow has filled in areas that were previously 240 meters deep, Zoeller said. Beyond that point, ocean depths increase steeply, making it difficult to measure the lava’s path on the ocean floor. “We do think that the flow extends offshore underwater for some distance,” he said.
Aside from the stretch of land between the high tide and low tide marks, which is public, new land created by lava legally belongs to the state of Hawaii, falling under the jurisdiction of the state Department of Land and Natural Resources, said department spokeswoman Deborah Ward. Although the new shoreline appears solid, it isn’t stable, HVO scientists warned. The platform of lava is built on a foundation of loose rubble and could shift or collapse into the ocean.
3. Halema‘uma‘u Crater Is Getting Wider and Deeper
As lava drains out of fissures on the volcano’s eastern flank, magma reservoirs beneath the summit are deflating. That subsidence, combined with a series of underground explosions thought to be triggered by the interaction between magma and water, have led to dramatic changes at Halema’uma’u, the crater within Kīlauea Caldera at the volcano’s summit.
“It’s enormously larger,” said Kyle Anderson, a research geophysicist with the USGS, who has been on site at HVO since early May. In fact, the crater’s cavity has grown in volume by around 10 times, increasing from around 64 million cubic meters before the eruption began to more than 600 million cubic meters today.
The changes began when the lava lake within the crater’s Overlook Vent began draining shortly after the eruption began. A sequence of rare explosive eruptions initially widened the vent from about 5 to 40 hectares, before causing it to collapse in on itself and disappear sometime in late May. Plumes of ash and steam prevented scientists from observing the process directly, but they used satellite imagery to track the changes.
Since then, the explosions have continued underground, with the crater floor sinking more than 450 meters over the past 2 months, and massive sections of wall falling into the crater in daily slumping events.
The last time such dramatic changes occurred at Kīlauea’s summit was 1924, when subsidence more than doubled the size of the crater after a similar series of explosions. But the scale of recent events far exceeds what happened 90 years ago, Anderson noted.
“In historic times this is really unprecedented,” he said. “Nothing like this has been observed with modern instruments.”
To measure and map the changes, scientists use drones to take images that are stitched together to make 3-D topographic models of the crater. They also use GPS, radar range finders, and thermal cameras to record changes, and they are in the process of placing cameras around the crater rim to collect more images of collapse events. A video compilation of some of these efforts can be seen below:
Scientists, now based at the Volcano House hotel about 3 kilometers from the crater, after abandoning HVO headquarters because of hazardous conditions in May, wait for the periods of quiet that follow a slumping event to retrieve samples or place instruments in the field.
The eruption has led to some technological casualties. “As the crater has widened, it’s taken a couple of our instruments with it,” Anderson said.
4. Lava Has Wiped Three Communities off the Map
Even as scientists have worked around the clock to document geological changes at Kīlauea that haven’t been seen in nearly 100 years, they remain acutely aware of the most painful changes caused by the eruption: the destruction of three communities. Flows have buried hundreds of homes in several neighborhoods of Leilani Estates. The subdivisions of Kapoho Beach Lots and Vacationland are almost completely gone, swallowed by lava.
Before the current disaster, the most destructive period of the volcano’s recent history was a flow that buried the village of Kalapana in 1990.
Although that event destroyed some 100 homes over a period of 9 months, the 2018 eruption has been far more devastating, wiping out more than 650 homes in just a few weeks, including a home owned by Hawai‘i Island mayor Harry Kim. In the wakes of these flows, thousands of residents are now displaced.
To keep an accurate tally of the number of destroyed homes, Hawai‘i County housing officials reconcile property tax records with aerial surveys of the area. “That’s the challenge,” said Hawai‘i County Civil Defense spokeswoman Janet Snyder. “It takes time, but the effort to verify and get it right is important.”
From the mountain summit to the coast, HVO scientists are working together to map the dramatic changes that Kīlauea is bringing to the landscape of Hawai‘i Island. With the eruption now in its 13th week and showing no signs of slowing down, those changes are expected to continue.
Loomis, I. (2018), Four ways Kīlauea is redrawing the map, Eos, 99, https://doi.org/10.1029/2018EO103371. Published on 27 July 2018.
Text © 2018. The authors. CC BY-NC-ND 3.0
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