ambience: volcanic eruption, Hawaii
Volcanoes are, in a sense, status reports – live updates from the interior of our planet. In a volcanic eruption, magma rises from the depths of the Earth, bringing with it clues about what’s happening deep below our feet. I’m Jim Metzner, and this is the Pulse of the Planet.
“Not only are volcanic eruptions amazing features to observe but volcanoes have been called windows into the interior of the earth by geologists.”
Jim Webster is a curator at the American Museum of Natural History where the Hall of Planet Earth opens this month. He tells us that volcanic eruptions bring up magma from inside the earth.
“Magmas come from the inner earth. Some come from the mantle, which is that portion of the inner earth which is immediately below the crust, that which we see on the surface. Some magmas are actually generated in the lower parts of the crust. The presence of magma at surface tells us that there’s heat within the earth. Temperatures high enough to melt rock, to allow the magma to become less dense and rise towards the surface.”
Billions of years of heat producing reactions have left their mark on the Earth’s interior. But some of this heat is also created by the movements of the sun and moon.
“Just as the sun and moon pull on the oceans and cause tidal distortion of the oceans, it’s known for a fact that these very same bodies cause tidal distortion of the rocks in the earth. So, the slow expansion and contraction of the solid rocks of the earth as a function of the gravitational pull of the sun and moon. Now, the gravitational distortion is much, much smaller than what the oceans and seas show. But this slow movement actually generates heat within the earth too.”
Pulse of the Planet is presented by the National Science Foundation. I’m Jim Metzner.