This is a partial transcript from "On the Record," December 27, 2004, that has been edited for clarity.

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UMA PEMMARAJU, GUEST HOST: Well, lots of questions tonight about this catastrophe and how this massive earthquake triggered the powerful tsunamis (search). Right now, we know that nine countries have had coastal communities simply wiped out. Were there warning signs, and could more a have been done to alert people in Asia? Joining us from Seattle, geologist Brian Atwater with the U.S. Geological Survey.

Welcome. Nice to have you here.

BRIAN ATWATER, GEOLOGIST: Thank you, Uma.

PEMMARAJU: First off, many people really don't understand just how powerful these tsunamis can be. Explain, if you will, what happened in this case.

ATWATER: What happened in this case was a great shift of two of the plates that make up the earth's outer shell, one of them shifting up over the other and moving the sea above it and sending off the tsunami in that fashion. The places near the earthquake, of course, were damaged not only by the earthquake itself, but by the tsunami, and then places far away were taken by surprise by the tsunami.

PEMMARAJU: Earlier today, the head of Italy's National Geographic Physics Institute said that the quake even disturbed the earth's rotation. How is this possible?

ATWATER: There's a record of this also with, for instance, the 20th century's largest earthquake in Chile in 1960, where the earth's rotational wobble was actually nudged by the earthquake. It happens. It was such a big event, the fourth largest earthquake since 1900.

PEMMARAJU: We're also hearing reports, of course, of complete coastal communities being wiped out and some islands actually moving about 100 feet.

ATWATER: The islands moving about 100 feet? I'm sorry. I'm just not familiar with the details on that part of it. The tsunami washing across islands would be expected if they're low-lying. As for land moving, though, keep in mind, that when these plates shift that they are moving the land surface above them. There are measurements from Alaska, from the 1964 Alaska earthquake of magnitude 9.2, of land having shifted seaward about 60 feet during that earthquake. So I'm not sure, but perhaps that's the kind of information you're dealing with on the islands.

PEMMARAJU: Lots of talk tonight about warning signs, the fact that people should have been warned somehow that this was about to take place. How realistic would it have been, really, to get a warning out that the tsunami was on its way?

ATWATER: Well, for the people there in Sumatra and on the islands to the north, those people had a natural warning, the earthquake itself. And their only challenge then would be to be able to get to high ground, out of the way of the tsunami, if there was high ground on their island.

As for people further away, too far to feel the earthquake, they're the ones who needed the tsunami warning. And certainly, the capability exists to deliver a warning quickly. Such a capability has been developed and improved upon in the Pacific Ocean, and so most of the Pacific Rim communities are protected by that now. That kind of system obviously needs to be in place in the Indian Ocean, as well.

PEMMARAJU: It could have made a big difference. All right, Brian, thanks so much for joining us with your perspective. We appreciate it.

ATWATER: Thank you, Uma.

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