Beacon Rock

 

Beacon Rock is an 800' rock monolith standing on the north bank of the Columbia just downstream of Bonneville Dam. It's also a State Park and there is an amazing trail that zigzags its way up to the top.

We had detoured east from the I-5 Corridor to visit the Columbia Gorge on our way down to Portland - it was the first time in a very long time (maybe ever?) that we had driven the Washington side of the river through this section. After Beacon Rock, we passed the dam and crossed the Bridge of the Gods to Oregon. Where most slopes were charred from last year's fires.

The gorge is carved through Columbia River Basalts, which flowed this way to reach the sea before much of the modern Cascades formed. The lava flows are many millions of years old, whereas Beacon Rock is a basalt plug that formed the core of a small volcano a little more than 50,000 years ago. Very different stories.

This section of the Columbia Gorge has a rich geologic history. Besides its volcanic features, the canyon is significant in that the Columbia is the only river between the Fraser and the Klamath that cuts through the Cascade Range, which otherwise forms a stark drainage divide between the damp coast and the dry interior. At the end of the last ice age (less than 20,000 years ago), as many as 100 catastrophic floods rushed through the Gorge as Lake Missoula repeatedly emptied out from behind its ice dam in northern Idaho. And then, just a few hundred years ago, a huge landslide occurred on this side of the river just above Bonneville, pushing the river to the south side of valley. Interestingly, the dam right is built right at the toe of this large slide.