FIELD TRIP SIDETRIP H - Anderson Butte, Baker River

A view of Bacon Peak and its cap of Eocene sediments

From the summit of Anderson Butte (an easy hike of about 1.8 miles and 1,000 feet of climbing from the Anderson Lakes trailhead), the traveler has great views of mountains carved from rocks of the Western Domain. Almost directly east is Bacon Peak, a massif carved from rocks of the Easton terrane (Shuksan Greenschist and Darrington Phyllite) and capped by 50 million-year-old sandstone and conglomerate of the Eocene extensional event. During the Eocene extensional event, faulting and stretching of the crust produced low areas--valleys--that were filled up with sand and gravel by streams. Geologists do not know how much of the immediate area was once covered by the stream deposits, and most have been eroded away except for patches like that on Bacon Peak, which were faulted down into the older, harder rocks and therefore somewhat protected from erosion.

View from true summit of Anderson Butte looking east to Bacon Peak and sandstone beds (yellow) lying on rocks of Easton terrane. A small arc-root pluton of granodiorite (pink) intrudes the older rocks.