Glacial Erratics – Remnants of the Ice Age

Towards the end of the last Ice Age a huge ice dam collapsed causing a 3000 square mile lake to drain. The destruction caused by this cataclysm can still be seen throughout the Pacific Northwest. The Columbia River Gorge is a product of this great ravaging wave of water, and many unique features along the route are a testament to it’s effects.

One of the more unique effects of this great flood are the number of “Glacial Erratics” strewn about the country side. These glacial erratics are chunks of rock that hitched a ride in pieces of ice broken off during the flood. One of the larger ones found is located about eight and a half miles South West of McMinnville Oregon off of SW Oldsville Road at Erratic Rock State Natural Site.

Direction sign to the rock

Oregon Geology Sign

A small sign is set here, it says: “The 90-ton glacial erratic rock at the top of this 1/4-mile-long trail is a stranger from a distant location – it was transported here thousands of years ago on an iceberg in the wake of a cataclysmic flood.

“During the last Ice Age, 13,000-15,500 years ago, a giant glacier dammed the Clark Fork River in what is today southwest Montana and created a huge lake – Glacial Lake Missoula. At 3,000 square miles, the lake held nearly 500 cubic miles of water.

“Rising waters collapsed the ice dam several times, releasing tremendous torrents of water across eastern Washington and down the Columbia River toward the Pacific Ocean. Floodwaters nearly 1,000 feet deep surged through the Columbia River Gorge and flooded the Willamette Valley.

“Flowing with 10 times the combined annual volume of all the Earth’s rivers, floodwaters raged at 60 miles per hour, stripping away up to 200 feet of topsoil and ripping huge boulders from the underlying bedrock. The floods also carried boulder-laden icebergs – as the ice melted and the floodwaters receded, boulders, called “glacial erratics,” remained stranded in fields and prairies.

“The boulder at the top of this trail is the largest known glacial erratic among the hundreds found in the Willamette Valley.”

A look back at the park entrance.

and a look up the hill along the path to the errant boulder.

The boulder itself

But the view from this little hill top is quite nice. This was in the fall, I can only imagine what it looks like in the spring with freshly blooming fields laid out below.

View for miles

Know of any other glacial erratics in the Pacific Northwest? Please comment below!