Lava is the most famous hazard of volcanoes. It is featured in movies. It used to describe lamps. It is used to describe chocolate cakes. And it is used to describe mobile phone cases. But lava is only part of the volcano story. 

Lava is what we call magma. This is when it flows out of a volcano. Magma is molten - or melted - rock. You would not want to stand in lava. It can be as hot as 2,000 Fahrenheit. At a walking pace you could outrun the majority of lava flows. So, what’s so hazardous about a volcanic eruption?

Sometimes magma does not flow out of a volcano. Instead, it explodes. It is an exploding mixture of hot gas, magma, and rock. When it comes out, it is fast. It is also unpredictable. 

In an explosive eruption, pieces of hardening magma and rock are spewed upward. They form a hot plume of gas. They range from the tiny particles that make up volcanic ash to chunks the size of cars. As the plume blows downwind, it drops materials like a hail storm. It litters the landscape with volcanic rocks. A pyroclastic flow of hot gases carrying the heavier material may pick up speed. This happens as it sweeps down from the volcano. As the flow mixes with the surrounding air, lighter ash may get lofted up in a cloud. It can travel as far as thousands of miles. 

The bigger chunks are an immediate hazard to people and wildlife around the volcano. But the cloud of ash takes a long-term toll. It can be devastating. In 1980 Mount St. Helens erupted. It is in Washington state. It produced a pyroclastic flow. It scoured the landscape at speeds up to 600 miles per hour. It lofted ash that settled on 11 states over the next few days. 

In 2010 Iceland’s Eyjafjallajökull volcano erupted. It sparked electrical storms. It had an ash plume more than 5 miles high. It spread over Europe. It grounded airline travel for days. 

Geologists who study volcanoes and called volcanologists. They are trying to better understand the behavior of these pyroclastic currents. It is dangerous to capture data directly from an explosive eruption. So volcanologists have found ways to capture data from a distance. They simulate flows in laboratories. Smithsonian’s Dr. Ben Andrews' Eruption Simulator uses laser beams. It also uses talcum powder. He can observe how erupted materials get distributed upward and outward in different scenarios.  

Learn more about Ben’s volcano research in the "Smithsonian Science How" webcast. It is on Thursday, Dec. 14, 2017. Watch How Volcanic Eruptions Send Materials Up and Out. It airs at 11 a.m. and 2 p.m. EST. It is on the Q?rius website. Ben will take you on an explosive journey. He will answer your questions live. You can also get teaching resources to use with the webcast.