By Dave Tucker September 29, 2010
The most recent post on the entertaining Magma Cum Laude blog, by Jessica Ball [aka ‘Tuff Cookie’] states:
“Perhaps we should submit a request for a Columnar Jointing Week to someone in Washington.” Maybe she means a Presidential dictum for ‘National Columnar Jointing Week’.
Okay, well, I’m “someone in Washington”– State, that is. I can’t issue any dicta whatsoever, so will reinterpret her ‘challenge’ to show off some photos of columns from Washington State. This won’t be a field trip on the Northwest Geology Field Trips website just yet. I’ll work these various stories and photos into future field trips. Click any photo to enlarge it.
Pinus Lake andesite, Mount Baker (Hildreth and others, 2003). I already wrote up a field trip to this orphan andesite lava, with the spectacular columns rising above the Mount Baker Highway. Here’s the photo again.
Here are some more andesite columns, in the Table Mountain lava flows of Heather Meadows near Mount Baker. This flow is similar in age to that of Pinus Plateau, around 300,000 years old. It erupted from a vent on Ptarmigan Ridge, and forms the inverted topography of Table Mountain between Mount Baker and Mount Shuksan.
The Table Mountain lava (Hildreth and others, 2003) has stubby columns at the lowest elevation exposures, shown above. However, higher up, the lava has much skinnier columns, suggestive of cooling in contact with ice. Just above the Heather Meadows Visitor Center (USFS) are these wonderful columns right along the highway. They cooled against the steep valley wall. The radiating columns show that the cooling front was spreading out into the interior of the flow.
And how about these ice contact columns? These are in the 70,000 year old Portals andesite on the north wall of Rainbow Creek at Mount Baker.
Now, lest you think I am completely Baker-centric, here are some columns in a dacite lava near White Pass, south of Mount Rainier. These are in the Clear Fork Cowlitz River, and can be seen from a small interpretive site along US Highway 12 west of White Pass. The glaciated flow is around 650,000 years old (Pringle, 2008).
And then there is Beacon Rock, the 57,000-year-old (Evarts and others, 2009) eroded plug along the Columbia River just west of Bonneville Dam. The colonnaded south face of the rock rises 850′ above the river. The cinder cone that once surrounded this basaltic andesite plug was eroded by the catastrophic Missoula Floods.
Of course, the Columbia River Basalts provide quintessential examples of columns in Washington State. Here are some in the Grand Coulee, on the west shore of Lenore Lake (US 97).
Here’s a detail of the wildly diverging columns in the lower right of the photo above:
The Columbia River Basalts flowed out the ancestral Columbia River and radiated into southwestern Washington, too. Here are some columns in a quarry near Rainbow Falls State Park, which are west of Chehalis on US 12.
So, I’ve done my part to answer Tuff Cookie’s challenge. How about…Oregon? Or is it a matter of ‘seen some, you’ve seen ’em all?”
Evarts, R. C., Conway, R. M., Fleck, R. J., and Hagstrom, J. T., 2009, The Boring Volcanic Field of the Portland-Vancouver area, Oregon and Washington: tectonically anomalous forearc volcanism in an urban setting. In Volcanoes to Vineyards: Geologic Field Trips through the Dynamic Landscape of the Pacific Northwest, ed. J. E. O’Connor and others, 253-270. Boulder, Colo.: Geological Society of America.
Hildreth, W., Fierstein, J., and Lanphere, M., 2003, Eruptive history and chronology fo the Mount Baker Volcanic Field, Washington: Geological Society of America Bulletin v. 115 p.729-764.
Pringle, P., 2008, Roadside Geology of Mount Rainier National Park and Vicinity. Washington Division of Geology and Earth Resources, Information Circular 107.