Exploring Wildness

The Folding and Twisting of a Miocene Lava Flow

The Miocene Lava Flows have been folded and twisted in the Manastash Ridge. (Thomas Bancroft)

The Miocene Lava Flows have been folded and twisted in the Manastash Ridge. (Thomas Bancroft)

The basalt rocks rose from the roadside to the ridge on our right and ran down the hill to the valley below. Endless red-brown blocks the size of basketballs scattered the hillside with no vegetation growing between them. A few dead trunks had slid from the ridge top where hemlocks, pines, and firs dotted the crest. The slope dropped down to a ravine, and Manastash Creek was out of sight over the edge of a steep bank. Then an abrupt cliff rose on the other side, the bottom part looked like folded cloth, rising to another ridge crest. Further down the valley was a stark promontory of basalt, making like a majestic head looking to the east.

The hillside was covered with small basalt lava rocks in the Manastash Ridge area of Wenatchee National Forest. (Thomas Bancroft)

The hillside was covered with small basalt lava rocks in the Manastash Ridge area of Wenatchee National Forest. (Thomas Bancroft)

In the Miocene, primarily between 14 and 17 million years ago, massive lava eruptions came from a series of fishers in eastern Washington and northeastern Oregon. The lava covered the Columbia Basin with a contiguous lake of molten rock, some even flowed out the Columbia River Gap. 

Here on Manatash Ridge, the Miocene basalt flows of the Columbia Plateau have been folded and twisted like so much licorice strips. The Yakima Fold Belt runs along the eastern slopes of the Cascades. This region was uplifted, twisted, folded, and manipulated like so much putty and now the hard basalt rocks have been exposed by the erosion of softer sedimentary elements. The Cascades are young mountains with much of their formation happening in the last ten or so million years.

We parked the car along Forest Service Road 31. The road ran down the Manastash Valley toward Ellensburg, Washington. This incredible piece of our geologic past stretched along both sides of the road in the Wenatchee National Forest. My body felt tense, heart racing, as I tried to imagine the formation of this landscape. The westward movement of the North American Tectonic Plate continues to push against the Pacific Plates creating the pressure that has caused the Cascades to grow. The dust from the road filled my nostrils, and a light breeze rolled down the valley while I stared across this landscape, mesmerized by its beauty and the geologic forces that have sculpted the landscape.

A large lava headwall at the end of a ridge line in the Wenatchee National Forest. (Thomas Bancroft)

A large lava headwall at the end of a ridge line in the Wenatchee National Forest. (Thomas Bancroft)

 

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