Northern Tier 2010

July 19, 2010

Moving Like a Glacier

Filed under: Geology, Montana, Section 02 — Henry Scott @ 8:00 pm

I slept in as long as I could today (7 a.m.) because it was a bit cold and cloudy, and then realized I didn’t have a sense for how to best use my time. Should I go for a hike? Proceed to another part of the park? I decided to go out for pancakes to think it over.

Somehow, things still weren’t clear after breakfast, and I thought about seeking the advice of a ranger. Right about then a park bus showed up on its way to the St. Mary visitor center, which was about five miles away (Glacier has a terrific, and free, public transportation system), so I hopped on. I spoke with a very helpful ranger, and she encouraged me to continue on to Many Glacier and hike to Grinnell Glacier.

As I waited for the return bus, it started to rain. Fortunately, I left my camp rain-ready when I went for breakfast, but it was still raining when I got back, so I parked myself in the tent to read and wait it out. Once the rain stopped I packed up and rode the 23 miles to Many Glacier and made camp. The ride took quite a while due to strong headwinds.

I got here too late for the hike to Grinnell Glacier, but I had enough daylight to head up to Ptarmigan Falls, which were incredible, but hard to photograph. Along the way, however, there were many good outcroppings of the Grinnell formation of the Belt Supergroup.

The rocks in this formation are mostly fine-grained sedimentary deposits with a deep red color due to the presence of some oxidized iron. They clearly formed during a long period of time for which much of the Belt sea was shallow water that periodically dried up, only to be re-flooded, as indicated by numerous preserved ripple marks and mud cracks. These rocks are overlain by deep-water deposits such as limestone, so we know sea level was ultimately on the rise, but within the Grinnell formation there appears to have been a long transitional period because there are occasionally interbedded green layers which suggest the more reducing conditions of slightly deeper water.

I’m currently trapped in my tent while it rains again, but that’s okay because I’m ready for bed, and I love the sound of rain on the tent. I just hope the weather will be good tomorrow!


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