View of Mt. Mazama Pumice Flow

Tephra from Mt. Mazama's Climactic Eruption

It was one of Oregon’s highest peaks, over 12,000’ in elevation. It was taller than Mt. Hood and more massive than Mt. Jefferson. But in a matter of hours 7,700 years ago, it disappeared in one cataclysmic explosion, sending ash deposits as far away as Canada and hot pumice flows hundreds of feet thick up to 25 miles from today’s Crater Lake. The distinctive, white-colored signature layer of these tephra deposits can be found throughout Central Oregon today, revealing itself at trailside or on riverbanks when least expected.
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Panoramic View of Balanced Rocks

Balanced Rocks of the Lower Metolius Canyon

Hidden and nearly unnoticed in the canyon lands above the Metolius River arm of Lake Billy Chinook are several small bowls with unique geologic formations, known as the “balanced rocks.” Carved by erosion over eons of time, these great slabs of rock weighing many tons are poised up to thirty feet in the air above pinnacles of softer rock. First recorded in 1855 by a railroad survey party traveling in the area, these balanced rock formations are accessible today by a short hike from a good road about thirty driving miles west of Culver.
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Mima Mound with Rock Ring

Mima Mounds - A Mystery on the Shaniko Plateau

In our scientific age, it’s hard to believe that the origins of any landform could still be unexplained, but this is the case with the extensive soil mounds and their encircling rock rings found northeast of Madras on the Shaniko Plateau. Known as mima (my-muh) mounds, several theories have been advanced about their formation, from differential erosion, to Ice Age freeze-thaw cycles, to soil movement by foraging gophers. But no one theory is widely accepted and these unusual land features remain a puzzle to geologists today. Hundreds of acres of this mima mound topography can be explored on BLM land near Shaniko.
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Panoramic Photo of Tumuli Lava

Tumuli Lava - A Backdoor into the Badlands

What are tumuli (besides the plural of tumulus)? From the Latin tumidus, meaning swollen or bulging in shape, a tumulus is a circular, domed lava structure up to 30’ high and 60’ in diameter, formed by the upward pressure of actively-flowing lava against its cooling crust. Along with its elongated cousin, the pressure ridge, these fascinating lava formations can be explored on a less-traveled trail in the Badlands Wilderness, just 15 miles east of Bend.
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Panoramic View of Sand Canyon

Pinnacles of Wheeler and Sand Canyons

Some of the more geologically and visually interesting canyons in Central Oregon are found on the southeast slopes of the Crater Lake caldera. In these lightly-visited canyons are found hundreds of stark stone pinnacles, which have eroded out of the volcanic ash of remnant Mount Mazama. The pinnacles in Wheeler Canyon are easily accessible by car at a viewpoint in Crater Lake National Park, while the rock towers in lower Sand Canyon require a challenging, cross-country bushwhack of 2.7 miles roundtrip.
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