New York —
After the burning lake of lava drained and the ground fell, water has accumulated in the Halema‘uma‘u crater on the Big Island of Hawaii. This may lead to an explosive eruption … or not.
The photos show the change in the Kilauea summit caldera, from April 2018 to May 2020.
Joshua Stevens / Earth Observatory / NASA
Between 2010 and 2018, a large lake of lava bubbled and splattered within the caldera of the summit of the Kilauea volcano in Hawaii.
Then, in May 2018, as part of a larger eruption that spewed lava from the fissures eastward, the lake quickly drained and part of the caldera floor collapsed. This left a hole almost as deep as the One World Trade Center.
But that was it. For about a year, the much deeper and wider Halema‘uma‘u crater was relatively quiet.
But in July 2019, helicopter pilots began noticing that water was collecting in a pond at the bottom of the crater.
Water levels have steadily increased since then.
Today, the lake, now with a rusty brown glow on its surface due to chemical reactions taking place in the water, has an area larger than five soccer fields combined and a maximum depth of approximately 30 meters (100 feet).
The satellite image sequence shown above shows Halema‘uma‘u crater before draining the lava lake (left), after the collapse of the caldera floor (center), and after water accumulated on the crater floor for nine months (right). The Operational Land Imager (OLI) instrument in Landsat 8 acquired all three images in natural color.
When the lava lake was present, it appeared in the southeastern part of Halema‘uma‘u, although a partially solidified lava crust on its surface, making it appear gray from above. (The light gray circular area with a thin rising column of volcanic emissions marks the location of the lake.)
After the caldera collapsed, the terrain surrounding the lake changed dramatically, including the formation of a new 140-meter cliff (thin, dark line) north of the crater.
In the final image, the pond at the summit looks small from Landsat’s perspective (30 meters per pixel). The photograph below, taken on April 21, offers a better sense of scale.
Image of Halema‘uma‘u Crater Lake from April 21 to May 3, 2020. Courtesy Matthew Patrick / USGS
The explanation for the new pond is simple
“We have a drilling well just over a kilometer south of the crater where we measure the level of the water table,” he explained. Don Swanson, a volcanologist at the Hawaiian Volcano Observatory of the United States Geological Survey (USGS). “We know that the crater floor fell a little over 70 meters below the water table in 2018. Every time you drill a hole below the level of the water table, the water will eventually enter and fill that hole.”
Explaining what the new pond means to the volcano is where the story becomes more complicated and interesting.
One of the key factors controlling explosive volcanic eruptions is the amount of water and other gases trapped within the magma.
If magma has many dissolved gases and vapor, explosive pressures and eruptions can be generated. If not, lava tends to flow smoothly from fissures in the ground, as has been the case in Kilauea for the past 200 years.
The calm eruptions of the Kilauea volcano are the exception, not the norm.
The cone eruption at Kilauea Fissure 8 continues on June 24, 2018. USGS
In the last 2,500 years, Kilauea has exploded explosively about 60% of the timeSwanson noted.
There are two scenarios that could lead to an explosive eruption. “In one case, magma could quickly ascend through the conduit and intersect with the lake,” Swanson said. “In the second, the crater floor could collapse and drop all the water into an area where it would quickly heat up in steam.”
But that does not mean that the next eruption is explosive.
“The next eruption could happen slowly and the water could evaporate,” he said. “We do not want to be alarmists, but we must also point out to the public that there is an increasing possibility of explosive eruptions in Kilauea,” Swanson said.
One thing’s for sure: Geologists will closely monitor Kilauea and its new lake with all the tools available, including seismometers, thermal cameras, drones, helicopter surveys, and satellites.
“Is the volcano in the process of returning to an explosive period that can last for centuries?” Swanson said. “Or is it just a small problem, and are we going back to the silent lava flows like we had during the 19th and 20th centuries? Only time will tell. ”
With information from the NASA Earth Observatory