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Home Archived Aug 4, 2016

USGS Geology in the Parks

Field trip map 2; Baker River

FIELD SIDETRIP G - Railroad Grade; off the Schriebers Meadow Road, Baker River

View from atop a glacial moraine

view from RR grade
Panoramic view to the south from Railroad Grade Moraine

Leave the Park Butte Trail after it reaches high meadows above a stiff switchback and take the Railroad Grade trail to gain wonderful views of volcanic and glacial features. The panorama from the moraine takes in the Easton Glacier, today well-retreated from its glory days as represented by the lateral moraine that provides this viewpoint. The relative smoothly ascending ridge of the moraine, which inspires its name, mimics the surface of the glacier that deposited it. Down the valley of Rocky Creek, the barren glacial debris gives way to brush and forest. Farther on down the valley (beyond the well hidden parking area at Schriebers Meadow), a slight hump in the forested terrain is actually a small volcano--really a cinder cone--that gave vent to the Sulphur Creek lava flow that flooded the lower end of the Rocky and Sulphur Creek valleys and continued on down to Baker Lake.


View of Black Buttes
Looking towards Black Buttes from the Railroad Grade moraine.

Look up the mountain to the northwest, to see the dark crags of Black Buttes, an ancient volcano that grew and was eroded before Mount Baker burst forth. Black Butte lavas are about 300,000 to 500,000 years old, whereas lavas from Mount Baker itself are probably all younger than about 30,000 years. Look south to see mountains carved from rocks hundreds of millions of years older than Mount Baker lavas. Across Rocky Creek are the ridges of Loomis Mountain, carved from an old volcanic arc of the Chilliwack River terrane. These rocks range from about 150 to 400 million years old. Park Butte, in the near foreground on the west, is carved from a block of ancient gneiss and other rocks of the Yellow Aster complex. The block of ancient gneiss is incorporated in the Bell Pass mélange and lies on a nearly horizontal fault above the Chilliwack River terrane. To the west in the distance are the peaks of the Twin Sisters massif, a huge piece of the Earth’s mantle that is also caught up in the Bell Pass mélange. In good viewing light the orange hue of the dunite making up Twin Sisters is a striking contrast to other old rock in view, which is all black, grey, and brown.

On to Anderson Creek Overlook

Material in this site has been adapted from a book, Geology of the North Cascades: A Mountain Mosaic by R. Tabor and R. Haugerud, of the USGS, with drawings by Anne Crowder. It is published by The Mountaineers, Seattle.

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