Tuesday, December 22, 2015

Lateral Moraines and Boulders Above the Columbia

Finally got around to fixing a couple of glitches on the blog so I changed the banner picture as well while I was at it.

The pictures is from the upper slopes above the east side of the Columbia River across the river from Chelan. The slope consists of lateral moraines from the Okanogan ice lobe that covered the plateau to the east. As the ice retreated from the area a series of lateral moraines were left behind marking sort pauses of the ice retreat.

The massive boulders are nearly all basalt plucked from the top edge of the plateau. Technically most of them are glacial erratics in that the the underlying bedrock under the moraines is much older orthogneiss and granite.

The picture was taken in late spring while the grass was still green. This area is susceptible to wildland fire. It is wet enough for some pine trees on the upper slope but the fire recurrence in this area is fairly frequent and has minimized the tree establishment. This area partially burned last summer.

No comments: