Excerpted Interview with Mike
Rhodes, Geologist with the University of Massachusetts:
NOVA: What's it like to be right next to an active volcano?
RHODES: It's really impressive. The sound and the vibration of the eruption
take over your body and it's a very moving experience. There's the intense
heat, particularly if the wind's blowing the heat off a lava flow. It's very
difficult to get close. There's all the sounds. There's the smell of the
gases that tend to make you choke, make your eyes water, your nose run, things
like that. And there's always this sort of sense of excitement, bordering on
fear or at least certainly awareness and concern for one's safety and what one
NOVA: Do you ever get used to it?
RHODES: I don't. Maybe some people do but I certainly don't. I'm always
conscious of what I'm doing and somewhat nervous about what I'm doing too.
NOVA: What is lava?
RHODES: Lava is a molten rock. It's rock which has been heated above its
melting point such that it can flow and be ejected into the air.
NOVA: And is it the same thing as magma?
RHODES: It's essentially the same. Geologists tend to use the term magma for
molten rock that hasn't yet arrived at the surface. When it erupts the same
material is referred to as lava.
NOVA: Is it moving?
RHODES: Yes, it's sort of like a plastic in that it is actually flowing. It
is actually moving in the same way as a stream flows or a glacier flows. But
we wouldn't recognize it as flowing.
NOVA: What does mantle look like?
RHODES: The mantle is solid. It's flowing at very slow speeds, maybe a few
centimeters a year. It's crystalline. It's got identifiable minerals in it,
and as this is slowly moving upwards from the depth within the mantle, the
pressure gradually decreases and at some point it will begin to melt and would
in fact then produce a magma, or lava.
NOVA: How hot is that mantle material?
RHODES: It's probably in the order of about 1400, 1500 degrees centigrade
(2500 degrees Fahrenheit).
NOVA: Why are these (Hawaiian) islands here?
RHODES: Well, there are a number of islands in different parts of the world
where volcanos are forming and gradually building up the land masses and
producing islands. In addition to Hawaii, good examples include Réunion
in the Indian Ocean, Iceland, the Galapagos Islands, Tristan da Cunha in the
South Atlantic. All of these are examples of volcanic activity that's creating
new land masses in the oceans.