The Aldergrove Glacial Erratic. source: geocaching.com
This is something a little different, leading to something cool: the NW Geology Blog has assembled quite a few self-guided geological fieldtrips, mostly in the Seattle to Vancouver corridor. There are two in the Fraser Valley: the Aldergrove glacial erratic, and the Shasta erratic in Coquitlam. The other BC field trip is to the recent, massive debris flow at Capricorn Creek.
But it was one of the Washington State trips which caught my eye though: a trip to a formation of Stilpnomelane at Blanchard Mountain, Skagit County, near Bellingham Washington. The reason this caught my eye: the formation is intersected by massive, green chert beds.
Northwest Coast Archaeology 