CORVALLIS, Ore. - An Oregon State University oceanographer has discovered remnants of an ancient forest in a seaside cliff near Yachats, Ore., with exposed tree sections that have been dated at older than 55,000 years.
Those trees, which apparently were flattened during an ancient landslide and preserved in sediment, are now being exposed - and may help shed light on the multuous historical natural conditions along the Oregon coast, researchers said.
Bill Smyth was on a family outing exploring the beach during a very low tide when he saw a layer of tree trunks exposed at an odd angle sticking out of the sea cliff between Yachats and Cape Perpetua. A layer of jumbled sediments and broken rocks above the trees suggests that the forest was buried in a landslide - possibly in connection with a major earthquake. A massive quake in the 8.5 to 9.0 range struck the southern coast in 1700.
But when the carbon dating was complete, Smyth and colleague Roger Hart, a former OSU oceanographer now working as a geologist for the Oregon Department of Geology and Mineral Industries, learned that the trees died at least 55,000 years ago.
And 55,000 years is as far back as that dating technique reliably works. The trees may be even older, said Smyth, who is an associate professor in OSU's College of Oceanic and Atmospheric Sciences.
"The age of the trees is impressive," Smyth said. "They may be 80,000 or even 100,000 years old. Getting a firmer date on the trees would be a nice piece of the puzzle in better understanding the tectonic history of the region."
But the trees also raise a question for scientists: Why are they being exposed now?
Since wood usually decays in a few decades - especially when battered by the marine elements - the exposure of the trees must be more recent.
"It looks to me like there has been erosion of the sea cliffs from waves," Hart said. "Why? That starts to get into the controversy. There's been at least one study that suggests that the wave height has been increasing, and it could be normal progression from sea levels rising.
"But there have been some other studies that suggest that we are getting a pattern of more persistent, stronger winds from the southwest," Hart added, "and that wind intensity and storm frequency have been increasing since about 1948. There's also the possibility that this is related to the Pacific Decadal Oscillation, a 20- to 25-year cycle of lower pressure in the northern Pacific that induces more wind and storms."
Hart was one of the lead scientists who analyzed newly exposed tree stumps that suddenly appeared on Oregon beaches in 1997. At the time, he said, they credited the sudden exposure to erosion caused by a strong El Nino event.
But El Nino erosions usually correct themselves within a year or two, Hart said, and many of the exposed trees are still visible. These trees, which at 7,000 years of age are much younger than Smyth's find, can still be viewed along the coast in places like Neskowin, where "more than 200 stumps are rooted on the beach, out in the waves," he said.
Smyth said it is hard to determine how many of the 55,000-year-old-plus trees are lodged in the slide area near Yachats, but he assumes the buried forest goes back quite a distance into the bank. His discovery is feeding the interest of scientists from several disciplines.
Smyth said that other researchers who have examined the trees - which appear to be some kind of spruce - are able to gather clues to the ancient atmosphere by deducing what kind of nourishment these trees may have had. Differences in the tree rings can suggest moist or dry years, giving clues to climate change.
An issue of immediate concern is why these ancient old spruce trees are suddenly greeting coastal visitors more than 55,000 years after getting buried in a landslide. Whether the answer lies in rising sea levels, more intense wave action, or a period of greater storm activity, the erosion could have serious implications.
Highway 101 lies only a few feet above where the trees are exposed, the researchers point out.
"One thing we need to remember is that the Oregon coast is constantly changing," Smyth said. "At times in our past, the sea level was much higher, and at other times, the coast line was miles out into where the ocean now is.
"If nothing else, these trees are a nice reminder that things don't remain the same forever."