Ancient Forest Underwater
DB: This is Earth and Sky on the subject of an ancient forest – underwater.
JB: You can look down and see this forest in a place called Clear Lake in Oregon. Clear Lake was formed when part of the Upper McKenzie River valley was dammed by lava flows from a volcanic eruption about 3,000 years ago. Three thousand years old is very young for a natural lake – but not as rare as you might think. The eruption at Mount St. Helens resulted in the formation of several large new lakes that are now only 21 years old.
DB: Clear Lake is aptly named. The water is crystal clear, and cold – it stays about 38 degrees year round. The water seeps into the lake from large springs, where melting snow from mountain peaks has filtered under ground through the fractured lava. The water’s cold temperature slows down decomposition. That’s why the trees that stood in the valley before the lake was formed still stand – a submerged forest of large preserved Douglas Firs. Radio-carbon dating shows that they’re almost 3,000 years old.
JB: Clear Lake is a place where you can go swimming in a forest. As you can imagine, the “underwater forest” is a popular destination for scuba divers. Today’s program was made possible by the National Fish and Wildlife Foundation, in cooperation with the U.S. Forest Service. We’re Block and Byrd for Earth and Sky.
Our thanks to the following individuals and institutions who assisted in the preparation of this script:
Dave Kretzing
Hydrologist
McKenzie and Blue River Ranger Districts Willamette National Forest
Mike Long,
Oregon Department of Transportation
The following books, articles and web sites were used in preparing this script:
Clear Lake Loop – Oregon Scenic Drives (GORP.com)
(@ mileage 72.4 Clear Lake turnoff)
Author’s Notes:
West of the Cascade Range, the Upper McKenzie Watershed has had a tumultuous history. Between 4 and 10 million years ago, Earth’s crust lifted up and created deep faults. As land rose, streams and rivers became steeper. The water sliced deep valleys. Flooding and lowering sea levels continued to scour out the valleys.
But other forces acted to fill in the valleys. As glaciers grew and shifted, the Cascades eroded somewhat, pouring material down into the valleys. Landslides also helped refill the valleys.
Remnanats of ancient glaciers can be found on the side slopes of the Three Sisters. Following the ice ages (about 12,000 years ago), volcanoes erupted. The lava and ash buried most of the glacial depsits. The flows filled some valleys and produced waterfalls, lakes and underground springs. Today, five glaciers remain in the area, covering about three square miles. The volanic eruptions continued up until about 1,500 years ago, leaving behind about 50 cinder cones.
The lake is deep and still – over 60 meters, or 200 feet, in some places. Divers learn to keep enough distance from the lake bottom to avoid stirring up sediment and reducing the clarity of the lake.
