ambience: lava flow
A slow moving river of fiery magma crackles as it flows over the charred crater of a Hawaiian volcano. In a moment we’ll take a look at some of the events which lead up to a volcanic eruption. I’m Jim Metzner, and this is the Pulse of the Planet.
Jim Webster is a curator at the American Museum of Natural History where the New Hall of Planet Earth opened recently.
“I think a very good analogy to understand explosive eruptions is using a seltzer water bottle. Magma is actually molten rock that contains dissolved concentrations of water and carbon dioxide — gaseous compounds that want to escape. A seltzer water bottle is actually liquid water that contains dissolved carbon dioxide inside the water. Now when you pop the top on the seltzer water bottle, that bit of confining pressure that’s in the air space between the water and the cap, that escapes when you open the bottle and you hear the sound as the gas is emitted and suddenly the water inside the seltzer water bottle is exposed to room pressure, a lower pressure. So the carbon dioxide that’s dissolved inside the water suddenly forms bubbles and starts to rise to the surface.”
As an example, let’s consider one of the biggest volcanic events in recent American history: the 1981 volcanic eruption of Mount St. Helens.
“During the 1981 eruption at Mount St. Helens there was a catastrophic landslide. A large portion of one side of the volcano surface slid away, and immediately exposed the underlying magma which, by the way, was gas charged. Water and carbon dioxide rich magma was suddenly exposed to atmospheric pressure. So the gas is attempting to escape very rapidly and gave this major catastrophic eruption.”
Pulse of the Planet is presented by the National Science Foundation. I’m Jim Metzner.