A USGS geologist collects a molten lava sample during a December 2015 lava flow from Puʻu ʻŌʻō.
Detailed Description
A USGS geologist collects a molten lava sample during a December 2015 lava flow from Puʻu ʻŌʻō. As the lava cools on the surface, its viscosity increases and the flow slows down. Credit: USGS.