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NOVA Online: Dating Lava
lava coveresd forrest NOVA: What exactly happens to the environment when lava flows?

LOCKWOOD: (Lava) pours down the mountain, probably at 1 or 2 miles an hour, covering lots and lots of ground. And most of the places where it covered the forest that existed, the trees that existed, that material is completely burned to ash.

NOVA: Your work has focused on the search for organic material embedded in old lava for carbon dating. When did you first discover the existence of organic matter in lava?

LOCKWOOD: The first time was an accident. My wife and I and the kids were at a picnic down on the south point of the island. And we could see a lava flow overlying that bed, on the other side of the bay. And we went over there to look at it, just out of curiosity. What does the base of a lava flow look like? And at the base of the flow, there were some roots. You know, nice big, obvious carbonaceous roots. They were a couple of centimeters in diameter. Anyone could see them. And that's a very rare occurrence. But that gave both of us the idea to start concentrating and looking for such localities. When I found my first charcoal sample in 1975, there had been 11 samples of charcoal found from beneath lava flows on this island. But they were all complete accidents. trees covered with lavaMostly in one place, in a graveyard, where people were digging through a particular lava flow, into a nice ash bed, easy to excavate for burying folks. Since 1975, I guess I've found something on the order of, oh, maybe perhaps 250, 300 charcoal samples. And those, sometimes they're dating the same flow more than once. What it actually means is that it was dated 175 different lava flows. So it's been very exciting because Mauna Loa now has by far the most refined chronology, prehistoric chronology of any volcano on earth. I don't think there's probably any volcano anywhere in the world that has more than a dozen or two, dated lava flows. We've got 200. So it means that Mauna Loa has become a library, an archive of well-dated lava flows. You know, biologists or physicists or anyone who wants to know what happened during those frozen bits of time 5000 years ago, or 10,000 years or for whatever time period, can come out here and ask me, do you have a lava flow about 7500 years old. scienic of HawaiiI want to know what the earth's magnetic field was, 7500 years ago. Well, I can punch my computer and say, yeah, there's three flows that fit that age range. And they can go out and take samples. And those lava flows, for example, will freeze the magnetic field that existed at that time. So it's a pretty remarkable.

NOVA: Does your work help predict volcanic activity that might affect nearby communities?

LOCKWOOD: The lava flows of Mauna Loa are highly fluid and they move long distances, the distance from up high on the risk zone of Mauna Loa, to the city of Hilo is over 50 kilometers. A flow in 1881 entered what are now the city limits of Hilo, reaching within 2 kilometers of the ocean. Such activities can happen again. And people who are worried about their investments, people that are setting property insurance rates, people that are worried about the future of Hilo (need to know) what the statistical odds are on Hilo being impacted by a lava flow. The only way that we can answer these questions is to understand the history of the volcano, not just the short historical period of history but the long term. That's why the radiocarbon dating program is so critically important because it enables us to determine when and where the volcano erupted in the past.



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