Working out on the tundra these days we don’t see much of the geology in the area because of all the snow. But as you look around at the mountains and the hills that run on all sides you are constantly reminded that there are a lot of forces at work here.
The hike up to Mt. Healy is pretty steep and get even more so! The wind made us turn around after an hour.
Immediately to the south of us is the Healy Range with Mt. Healy on the east side. The range is a result of tectonic forces creating the Hines Creek Fault and pushing up on the ridge. Elizabeth and I went hiking near Mt. Healy last week. Before we were turned away by some very strong and cold winds, we managed to look at some of the rock features along the trail and identify a few samples. At first, some of the rock looks polished and shiny, but upon closer inspection you can see that the luster is due to the minerals in the rock. Most of the samples we saw were pretty common schist. Among with the metamorphic schist we found many samples of quartz veins running through the rock in folds. The rocks with the silvery mineral appearance look that way due to the muscovite mica.
The rock is mostly metamorphic schist, but we found lots of quartz layered in.
The muscovite mica in this schist gives it luster and makes it look smooth.
To the east of the study site is the coalmine. The Usibelli Coal Mine was founded in 1943 and produces 1.5 million tons of coal each year. The coal that is mined here is called Lignite, and is very young coal at less than 20 million year old. Being this young, it has a lower carbon and energy content than older coals such as Bituminous Coal or even Anthracite, which is the oldest coal at over 300 million years old. This is the only coalmine operation in the state of Alaska today.
As we move from the cabin to the study site and back we pass another geologic feature, these are the erratics! Glacial erratics are rocks that have been carried by a glacier and then dropped in a place where the surrounding rock does not match. A rock like this can give good information about where it came from and how far it moved. This in turn tells us about the glacier that moved it.
This glacial erratic boulder may have been carried for hundreds of miles by the ice that was once in this valley.