Friday, October 14, 2011

Mt Baker cont

In previous posts, I wrote about our Rodeo Holliday trip that ended with a day at Heather Meadows on the side of Mt. Baker. The last notable thing about the trip was we had a great conversation about how science is supposed to work. At an earlier stop, I had pointed out the sun cups on top of the snow field, and mentioned that the how and why suncups form is a question that hasn't been completely answered. While exploring a snowbank Sam noted that there were suncup like features under the snowbank as well.

As we walked down the trail we made theories about how the suncup features would form on the bottom of a snowbank, and if the theories were testable. My theory was that it was based on the crystal structure of ice, but when pressed by Sam how I would test it, I did not have much of an answer. Her theory was the rocks under the snowbank (in the streams) initially forced the meltwater up over the rock creating the curved shape. Her test was to se if there was a correlation between cup location and size and an underlying rock.

At the next snowbank she ducked under to test her hypothesis

and sure enough there was a rough correlation between boulder location/size and suncup size. She repeated her observations at the next (last) snowfield we encountered and her subjective test held true. In the end she felt pretty proud she had come up with a theory that made more sense (to her) than her dad's and she was able to prove to him that she was right!

Wednesday, October 12, 2011

Mt Baker

In my previous post, I mentioned that on a Rodeo Holiday we went up to Heather Meadows on the Mt. Baker Highway. While we were there, we ran into a High School Geology class and the instructor pointed out to me that even though we couldn't see any mountains, there was some notable geology under foot.

Basically the canyon that forms drains Bagley Lake is a fault. On the west side of the lake is the Chilliwack River Terrane an accreted island arc, and on the east side are Mt. Baker Andesites. The Bagley Lakes trail parallels this drainage and crosses over a small dam, where you can see the difference in rocks from one side to the other.

Sam Looking at Mt. Baker Andesites

Sam Looking at Chilliwack Terrrane
  According to the USGS website on the Chilliwack Terrain, it is mostly phyllites and Greenstones that are thrust over the younger Nooksack Terrane.

Before the Chilliwack River terrane was thrust over the Nooksack terrane, its beds were folded upside down.
From: Terranes of the North Cascades: Chilliwack River Terrane
We saw a couple of nice metamorphic rocks on our hike. Admittedly the weather wasn't conducive to finding the best examples (and I am not great at identifying metamorphic rocks), but there were three areas that had distinctly different outcrops

Greenstone with quarts veins
Not sure with this one, originally thought it was a different metaconglomerate, but then thought about a fault Breccia, didn't know if that made sense. Help?
Though I certainly saw the difference between the rocks, I was in "Look at the Mountain and Glacial Features mode" so I'm not sure if I would have put together the drainage was a contact between terranes. So thank you to the unnamed HS teacher I met. It certainly made more sense to look at rocks than mountains on that foggy day.

Tuesday, October 11, 2011

Return of Fall

I am taking my Physical Geology students on a field trip today so I turned on the weather channel to see what the weather was going to be like. A screenshot from their website shows the weather forecast for our area.

A bit of good news for me! As we are headed for that little gap in the rain shown by the arrow!

 But another section of the map caught my eye, that light blue swatch of snow along the Washington/Canada border. This is the area around Mt. Baker Ski area, and when Sam, Stanton, and I took a trip up there during our Rodeo Holiday in mid-September spring had just arrived.

It had been a gorgeous warm fall, and on the beginning of the Rodeo Holiday trip we had taken advantage of weather and went to the San Juan Islands.

 Because the weather was nice, and we were about as close as we would ever be, I thought we'd extend our trip a day and go up the Mt. Baker Highway. Mt. Shuksan is one of those oft photographed Mountains, and I wanted to see it for myself. However, by the time we got to Heather Meadows Visitor Center, this was the view that greeted us.

We had actually intended to go all the way to Artist point, but the road to Artist Point did not open this year because the snow never melted. There were record snowfalls (over 900 inches) and when they went to plow the road in July there was still over 50 feet of snow over portions of the road. With all that snow, summer never really arrived. We saw one willow bush that was still in bud.

Because of the snow we went on two short hikes near the visitor center. One, The Fire and Ice trail, which has placards which presumably highlight geologic features of glaciers and volcanoes, only the placards had not been put in yet for the season. We did see lots of neat basalt columns.

The columns were tilted in many places 
so you could see the tops too. 

and a nice cirque/tarn at the end far of the trail.

Despite the lack of view and winter like weather, I had a good time looking at the rocks. In fact a HS geology class was up there at the same time we were, and the instructor told me about some geology to look for which I'll summarize in a future post.