Geologists map lava thickness

A preliminary map released this week by the U.S. Geological Survey shows the thickness of lava flows from Kilauea volcano’s most recent eruption.

The eruption began last May in Leilani Estates and destroyed more than 700 homes in lower Puna. It continued with vigor until early August, when lava flows began to cease.

According to the USGS, lava flows from 24 fissures buried an area of about 13.7 square miles and added about 875 acres of new land to the island.

Those flows vary in thickness.

The greatest thickness on land, at fissure 22, measured approximately 180 feet. And the greatest thickness in the lava delta, or the new land created where the lava entered the ocean, is approximately 919 feet, seaward from the Ahalanui warm ponds.

At fissure 8, the most active fissure in the eruption, lava is 167 feet thick.

Janet Babb, a geologist and spokeswoman for the USGS Hawaiian Volcano Observatory, said the thickness of the lava delta was something of interest.

In past instances when lava would enter the ocean, there often would be delta collapses because of steeper offshore slopes.

But because the offshore topography wasn’t as steep near Kapoho, the delta built out for quite a distance, and “in this case, we didn’t have any major delta collapse,” she said.

A final map will be released when all remote sensing data have been collected and processed, and current values on the map could change when data are finalized.

Babb said a lot of the data was collected by unmanned aerial vehicles and helicopters during peak activity last summer, but some areas were too far for the drones to fly or helicopters couldn’t fly because of laze plumes where the lava entered the water.

But now that the eruption has stopped, geologists can get the necessary data from those areas.

Additionally, USGS is “still looking at the entire flow field, still refining measurements done this summer,” Babb said.

“We’ll be studying this eruption for years,” she added. “There (are) a lot of studies still going on.”

However, the hope is to have a final thickness map completed in the next year, Babb said.

This is the first map related to the eruption that the USGS has released since August.

According to Babb, the map was created using about 1,500 aerial photos, which were used with software to produce a digital elevation model of the lava.

That model was compared to a digital elevation model of the pre-eruption ground surface. The difference between the two models is how the elevations were determined.

Email Stephanie Salmons at ssalmons@hawaiitribune-herald.com.
Source: Hawaii Tribune Herald