HVO scientists explain how lava flows cool

  • Janet Babb

The lava flows near Highway 132 could take decades to completely cool down, according to scientists.

Regardless of thickness, a lava flow will cool from the top down and from the bottom up, said Janet Babb, a geologist with the U.S. Geological Survey’s Hawaiian Volcano Observatory.

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When the surface of a lava flow “begins to cool and solidify, that solid rock acts as an insulator, slowing down the heat loss from all the lava below that,” she explained.

The thicker the lava flow, the longer it will take the interior to cool, said Babb. And while the interior rock can be solid, it can be “incandescently hot.”

HVO geophysicist Jim Kauahikaua said there was “nothing unusual” about the temperatures encountered as county crews work to clear Highway 132.

According to Kauahikaua, lava solidifies at about 1,000 degrees Celsius — a little more than 1,800 degrees Fahrenheit — so “you could have a very solid flow that’s still extremely hot, and that sounds like what they discovered out there.”

Road crews have encountered pockets of lava rock that reached 800 degrees Fahrenheit.

HVO said in a Feb. 28 “Volcano Watch” article that preliminary analyses of the 2018 eruption of Kilauea volcano’s lower East Rift Zone flow thicknesses suggest that the average flow thickness is between 33 feet and 50 feet.

Based on the cooling rate calculation, it could take roughly eight months to 1.5 years for flows of these thicknesses to solidify.

Meanwhile, solidification of flows ranging between 65 feet and 100 feet thick could take about 2.5-6 years.

The thickest lower East Rift Zone flows on land, which are approximately 180 feet thick, could roughly take 20 years to reach a completely solid state, HVO said.

Kauahikaua said lava in the Highway 132 area is estimated to be between 50 and 55 meters thick, or between 164 and 180 feet.

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These flows “won’t be completely cool for decades,” he said.

Email Stephanie Salmons at ssalmons@hawaiitribune-herald.com.

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