Volcanic necks (aka, chimneys, throats, plugs, etc.- I don't know if there's a "correct" term) such as this are pretty common in the Western Cascades, where thousands of feet of overlying volcanic and volcanic-derived debris has been removed by millions of years of erosion. For the most part, these "old Cascades" have not seen eruptive activity since the Pliocene, about 5 million years ago. The roughly cylindrical conduits that carried magma toward the surface, once cooled, are often more
A final panorama of this alteration zone, shot from the pullout on the opposite side of the road, which shows the gradient from more or less unaltered rock down the hill to very highly altered in the area of the calcite veins. From here, we'll walk down the hill to the curve visible on the far right. There's a couple of fun surprises waiting behind the Douglas firs along the right edge of the photo...Photo stitched in HugIn, otherwise unaltered. July 8, 2012. FlashEarth Location.