Wednesday, May 20, 2009

National Park stone: Mt. Rainier

I recently spent a very sunny weekend up at Mt. Rainier. We stayed at the Paradise Inn. Built during 1916 and 1917, the historic lodge is on the national register of historic places. It is an A-shaped building, a shape necessary to withstand the average of over 600 inches of snow per year. From a geologic point of view, the most impressive features are the three massive fireplaces, two in the main lobby and one in the kitchen.

Fireplace in Paradise Inn at Mt. Rainier

Each fireplace is made of various sized rough blocks of what appears to be granodiorite from the Tatoosh pluton. The pluton ranges in age between 26 and 14 million years old. I could not, however, find any information about which rock was used. The stones reportedly came from a local quarry.

One feature that stands out on several blocks is the row of drill holes. They show how the quarrymen made blocks by drilling a line of several-inch deep holes and dropping in two metal shims, each of which was bent at the top so the shims wouldn’t disappear into the cavity. He would then drop a wedge of steel between the shims and pound the row of plugs until the rock split on the perforation.

Close up of Mr. Tarbox's plug and feather quarrying method

Quarrymen call this the plug and feather method. It has used by stone masons for thousands of years though it has an interesting story in the US. According to quarry historians, a man named Mr. Tarbox introduced the method in this country in 1803. His work was noticed by a member of the commission to build a new jail in the Boston area, who tracked down Tarbox, hired him on spot, and got him to teach the method to other builders in the region. That knowledge spread quickly and soon the price of cut stone dropped appreciably.

The plug and feather method is still in use though it has been modified significantly with hydraulic air drills and hydraulic expanders. In places such as the Indiana limestone building district, quarrymen no longer need to swing a hammer.

Down lower on Mt. Rainier, at Longmire, another building makes use of the local stone, too. The visitor center is built of large boulders that must have been collected from the nearby river. The boulders are andesite, granodiorite, welded tuff, and rhyolite. Builders even used the boulders to make the chimney.

Longmire visitor center at Mt. Rainier
These buildings are two of many wonderful national park structures that use local rock, most often with rough cut faces or as boulders. Does anyone have any other favorite national park buildings with local materials?

1 comment:

Eric said...

Here's a picture of the rock fireplace at the Longmire Inn, courtesy of the Seattle Times:
http://seattletimes.nwsource.com/ABPub/zoom/html/2003593641.html
There's another rock picture as well with the story:
http://seattletimes.nwsource.com/html/outdoors/2003593640_nwwrainier011.html