Thursday, October 16, 2008

No Child Left Inside: 4th Graders in the Red Mountain Mining District

Last week I took a group of 4th Graders from a nearby elementary school to the old ghost town (I guess there aren't any new ones) of Ironton Colorado. This area is smack in the middle of the Red Mountain Mining District and has quite a few nearby mines to examine. Here we are standing on the tailings from the Larson Brothers mine. The mining district is pretty much right on the rim of the Silverton caldera, with the ore deposits all being associated with breccia pipes and the ring fault system at the rim of the caldera. Walking around the district you can see the remnants of the breccia pipes with small mines (and the occasional large one) at each base.

The kids were quite interested in the color of the water coming out of the mine and even though the chemistry was a bit over their heads, they got the idea that the pyrite oxidised into a strong acid. Then they all jumped over the stream so that the acid water wouldn't dissolve their shoes.

From here, we walked up valley into the town itself and then visited the renovated Colorado Boy headframe. The Colorado Historical Society has done an awesome job restoring the structure which I have shown to my college and high school classes on our field trips here. There is not much written about what was mined here beyond the usual, copper, silver and galena ores. It is also a great place to take a rest during a mid winter ski. This picture nor the next was of course not taken last week

Above the Colorado Boy is the remnants of an old wooden flume that transported a tailings slurry to the massive tailings pile in the valley bottom. The image here is the old suspension structure carrying the pipline across Corkscrew Gulch. Legend around here suggests that when this was made, it was the 2nd largest suspension bridge in Colorado. They engineered the pipeline so that it bowed upwards when there was no load and then during slurry operations it would assume the correct downward slant. Please don't cross the bridge now!

Tuesday, October 7, 2008

geologic time and the budget- An analogy of sorts


I was thinking about asking the Department of the Treasury for some help this semester in explaining exactly what 4.5 billion years looks like. They seem to have no problems with really large numbers. Here is a link to a story about the national debt clock being out of room.

Perhaps scientific notation will help? How many significant digits do you want?

Monday, October 6, 2008

Black Rocks

Last weekend was spent on a stretch of the Colorado River through Ruby and Horse thief Canyons. It was an awesome early fall day with warm daytime temperatures and the leaves just starting to turn.

Here, our flotilla is approaching the Black Rocks Monocline. Black rocks is the local name for...well, an outcrop of black rocks where this stretch of river sees its only rapid. I am not sure but it seems as if the Laramide left us more than our fair share of monoclines on the Colorado Plateau. My field work is very limited, but we seem to have a bunch. Anyway. The monocline shows a great bend in the Wingate-Kayenta-Chinle combination, much different from the usual flat lying cliffs we are used to seeing. Around the river bend will be the Black Rocks. These pre-Cambrian rocks are much harder than the Mesozoic sediments found everywhere else. The river channel in this section is much narrower, but deeper and the whole flow must squeeze through the channel creating a faster current, with some great hydraulics. I have seen whirlpools appear out of now where and just slap a canoe over, capsizing the boat and throwing dinner into the water, not to mention the two paddlers.

These rocks have been dated to 1.7 billion years old and it looks like a migmatic pegmatite with a few quartz veins shooting through (did I think of taking a close We had even camped one canyon up river with a great outcrop of the same material. Oh well, sitting right on top of this early Proterozoic black rock is the Mesozoic Chinle formation which clocks in at about 200 million years old. This trip was for fun, but every early summer I take a few geology-hungry K-12 teachers down this stretch and they love being able to stand on 1.5 billion years of missing Earth history. wow!