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Travels in Geology August 2004

Roving Oregon's dunes

Last Friday, the Mars Exploration Rover Opportunity took the closest images to date of dune fields on the floor of a martian crater. Scientists hope to send the rover to study the dunes, which are only a meter tall. But you don't need to leave Earth to get some out-of-this-world glimpses of dunes. The United States contains many remarkable dune fields including Great Sand Dunes, White Sands, Sleeping Bear Dunes, Jockey's Ridge and Oregon Dunes. Oregon Dunes is the largest coastal dune system in North America and visitors often see dune-buggies, rather than rovers, wandering the landscape that looks as alien as the scenes from Mars.

In this aerial photograph taken south of the Winchester Bay area, in Oregon Dunes National Recreation Area, vegetation grows in between transverse dunes. The introduction of non-native, invasive plant species threatens to completely cover the dunes in some locations. Image courtesy Darren Beckstrand and Errol Stock.

South of Florence and north of Coos Bay, Oregon Dunes National Recreation Area stretches for 42 miles along Oregon's coast. The area contains dunes up to 600 feet high and a wide variety of dune features. Oregon Dunes is easily accessible from Highway 101, part of the Pacific Coast Scenic Byway, and observant drivers can catch glimpses of the dunes as they speed along.

The many rivers flowing westward from the Coast Range, which runs from southern Alaska to California, delivered a large proportion of the sand that is now incorporated into the dunes. Scientists, however, are uncertain about the mechanisms that brought the sand together to form the dunes. One theory, says Darren Beckstrand, a geologic consultant who wrote his master's thesis on the Oregon Dunes while at Portland State University, is that retreating beach sand caused by sea-level rise in the Holocene accumulated as it moved inland and formed the dunes. The competing hypothesis, favored by Beckstrand, is that the sand was blown inland from the continental shelf during periods of low sea level in the Pleistocene.

The modern geologic features of the dunes are as interesting as its history, says Gayle Gill, an information assistant with the National Forest Service. In the winter, visitors can find rare occurrences of yardangs — elongate, wind-sculpted ridges — among the dunes. Intrepid hikers can also explore a field of heavily vegetated parabolic dunes in the Winchester Bay area. The tallest dunes are located along the John Dellenback trail, previously called the Umpqua dunes trail. For those who want to explore the dunes but loathe the idea of slugging through soft sand to see anything, a dune buggy is the perfect alternative.

NASA's Mars Exploration Rover Opportunity recently snapped this picture of small dunes on the floor of Endurance Crater. Dunes are common features in the martian landscape, and scientists hope to send the rovers to explore these features. Dunes are also common sites across the United States, including on Oregon's Coast. Image courtesy of NASA/JPL/Cornell.

Dune buggy/ATV rentals and guided trips are available at most of the surrounding commercial hubs — Reedsport, North Bend and Florence. The Spinreel Campground is the center of most off-road vehicle activity. About 50 percent of the dunes are open to off-road traffic, but the vehicles are restricted to areas that are not environmentally sensitive.

Sometimes, however, the reverse is true: The Forest Service has opened up vegetated areas to off-road vehicles for ecological reasons, Beckstrand says. For example, dune buggy traffic can help combat the invasion of non-native species of European beach grass by keeping the grass populations in check. "The areas of open sand have been rapidly decreasing over the last 30 to 40 years," he says.

If you are interested in visiting, you should consider planning a trip soon while the dunes are still largely free of vegetation. August is the peak tourist season, but Oregon's mild winters make the dunes enjoyable year-round, Gill says. September through October, with small crowds and early fall temperatures, may be the best time to visit. There is a day-use fee of $5 at most of the trailhead parking lots, but compared to the $1 billion it cost NASA to be able to drive Opportunity through the dunes on Mars, it is well worth it.

Jay Chapman
Geotimes Intern

Links:
Oregon Dunes National Recreation Area
Darren Beckstrand's Web site on Oregon Dunes
NASA website on Mars dunes

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