The visitor was at a 2001 gathering in Edinburgh, Scotland, called Earth System Processes, put on jointly by the Geological Society of America and the Geological Society of London. Such meetings are a carnival of science, and the research you see there is fresh, unpublished, speculative, even provocative. The presentations are considered useful snapshots but not formal publications that are reviewed beforehand by fellow scientists. So the latest Loch Ness theory, presented in a poster session by Luigi Piccardi, was nothing truly serious.
Piccardi argues that the myths and sacred places of the ancient Mediterranean, like the Delphic Oracle, owe a lot to geologic activity. At Edinburgh he extended his argument to Scotland. The earliest account of a monster in Loch Ness, from the seventh century, says that the Earth shook when the creature appeared and when it disappeared. And the lake happens to lie directly upon the active Great Glen earthquake fault. "In this light," Piccardi reasoned, "many modern eyewitness reports attributed to Nessie may find a simple natural explanation."
I think Piccardi's specific argument is wrong, but underneath lies a powerful truth.
It's true that earthquakes affect bodies of water. They create waves, both by directly shaking the water and by dislodging landslides on shore or in the muck below. Objects and gases in the bottom sediment can come to the surface. Quakes also may cause roaring or explosive noises. The seventh-century story could indeed have been prompted by an earthquake. Unfortunately, no earthquakes accompany the modern sightings of the Loch Ness phenomenon.
A better explanation for the goings-on in Loch Ness is another natural event called seiche ("saysh") that is common in long, cold lakes around the world. Think of a seiche as the giant-size equivalent of what happens when you get out of the bathtub: the water sloshes back and forth smoothly for a long time. Seiches are commonly caused by weather changes, after a sustained wind pushes the water to one side of the lake. When the wind stops, the water moves back and the slow sloshing begins. Seiches also happen from earthquakes, low-frequency motions from distant events that may be imperceptible to humans. (Here's an account of a swimming-pool "seiche" caused by the 1989 California earthquake.)
Once started, seiches can continue for more than a week, especially hidden internal waves that affect the dense layers of cold water at the lake bottom. Interactions with the bottom topography and surface winds, not to mention wave interferences, are all capable of causing roilings and eruptions in the water. So there's a viable theory already—and not just for Nessie, but for the "lake monsters" documented in large cold lakes around the world.
But to judge from Piccardi's actual poster (see the abstract here), he argued only that the monster legend may originate from an earthquake. That might be so. What sustains the legend is human nature.
Consider how people tend to animate the world: they give names and personalities to unusual rocks and formations, even venerate them. Piccardi has followed that insight to good effect in Greece. In a 2000 article in Geology he outlined the close ties between the temple of Apollo at Delphi, with its celebrated Oracle, and the major active fault directly beneath it. The sounds, smells, and motions of the site made a deep impression on the ancients.
At Loch Ness it would be easy to think that moving water must be due to a large living creature. As it happens, a tradition dating from the earliest peoples of Scotland centers around the water-horse or kelpie. That would be powerful reinforcement, once people had concluded there was a creature in the lake. And who can say which came first, the phenomenon or the agent? I know what I think: We see odd happenings in Loch Ness and make the most satisfying story from them.
Piccardi's scientific explanation of the Loch Ness monster is only satisfying in an intellectual way. And the ancient ways of seeing the world are still quite alive—just visit my colleagues the Urban Legends Guide and the Paranormal Guide. That is why after all the science meetings are over, Nessie will still have its believers.
PS: I've argued in another article that our innate drive to see pattern and personality everywhere underlies all kinds of Earth mysteries. A dry breed of skeptics fights that urge with futile fervor (for a sample, visit the About Atheism Guide), but for me the only sane viewpoint is to treat that anthropomorphizing tendency as a feature, not a bug, and enjoy the tug-of-war between head and heart. I will raise a toast to Nessie as an avatar, but not as an actual animal.