Weird new device measures how 'liquid' lava is

Last year, scientists and students from the University at Buffalo donned protective aluminized suits and got very close to the molten material spewing from Iceland's Litli-Hrútur volcano.

"It sounds like a bulldozer of broken glass coming your way," said volcanologist Stephan Kolzenburg.

While most people would avoid getting anywhere near a volcano, the team had an important reason to be there: trying out a brand-new device, a penetrometer that measures the viscosity of lava. A new study published in Review of Scientific Instruments discusses the penetrometer and data from its first use in the field—information never before gleaned from an active lava flow.

Limitations of laboratory lava

Lava is a mixture of three phases: melt, or molten rock; bubbles, or gas contained in the melt; and crystals, or solidified and cooled materials. Knowing lava's viscosity is key to better understanding how fast it flows. Higher-viscosity lava is thick and sticky; lower-viscosity lava moves more like a liquid, or a "river of fire."

The composition and viscosity of lava vary not only between volcanoes, but also with different characteristics in a single volcano, said Alan Whittington, a volcanologist who was not involved in the new study. For example, "hot lava is generally very fluid," he explained. "As lava cools down it becomes very, very sticky indeed."

Because of this complexity — not to mention the dangers of being so close to unpredictable material over 1,832 degrees Fahrenheit (1,000 degrees Celsius) — experiments to measure lava viscosity have been limited. Previous viscosity field studies and devices revealed information about lava at only one specific place and time.

Most research on lava viscosity is done in a laboratory setting where scientists can create lava of their own. While this type of experiment does yield important information about how lava might behave in nature, it remains a very controlled endeavor.