Sunday, June 6, 2010

Geologizing

Finding something to do to amuse myself in my off time can be a bit of a challenge here at Brooks Camp. I do have books to read and the occasional Netflix flick to watch on my laptop. Friday night I watched “Harold and Maude” which was made in 1971 when I was 19 but I had never seen it before. Great flick and the Cat Stevens soundtrack brought back hippie memories of my freshman year at the University of South Florida (Hi Barb!). Whatever happened to the guy who played Harold?

Other people at Brooks Camp often stay up late and play games and cards but that’s not really my gig. For fun, I can often be found checking the weather station for the day’s high and low temperatures and times of sunset and sunrise. But since that takes a total of, oh, maybe three minutes, I still must search out something to do to fill that void between dinner and going to bed when it is still light outside. And I’m not talking 8:30 p.m., either. This is the Land of the Midnight Sun, after all. Now at least I know what to expect when I finally get to Iceland. And btw - what latitude in the southern hemisphere is New Zealand?

I can’t really stay on the computer for hours, either. We have limited bandwidth out here in the Alaska bush and must share between at least 14 people the 2 Macs that have internet access. No big deal, though. I manage.

So I walk. No surprise here to those who know me! I walk around camp. I walk to the beach. I walk along the beach and back to camp. I walk to the bridge across Brooks River. I walk in the woods on the road to Lake Brooks and back - 2 miles round trip but watch out for the bears along the way. I saw a lynx one time. I walk in the woods on the trail to the falls platforms – same distance, same bears. I see a lot of spruce grouse, camouflaging themselves by not moving.

Spruce Grouse

I might be walking around and happen to look at my watch and it reads 10:30 p.m. OMG!!! It’s broad daylight out here! I’ve got to go to bed!

Saturday on my day off I went on a nice 3 mile round-trip hike up Dumpling Mountain with a group of visitors from Elderhostel. These people stopped so much and walked so slow it made me look good! We went up to the first overlook and on the way down I showed them where there is a bear den. It was drizzling rain and no wind when we started out around 9:30 this morning. When we were coming down off the mountain at 1:00 p.m. the winds had picked up to a strong breeze. By 5:00 p.m. the wind was blowing one-foot whitecaps on Naknek Lake. You just never know what the weather will do around here. I now believe that Alaska must have invented the phrase “If you don’t like the weather, wait 10 minutes and it will change!”

Iliak Arm from Dumpling Mountain

Back to the subject of things to do at Brooks Camp. My favorite pastime lately has been lobbing pieces of pumice into the lake and watching them float. Now, you may think BORING, that this is no big deal, but it is! Lobbing pumice is totally exciting! Pumice is really “frothy magma” when it is ejected explosively from a volcano and cools within seconds. This magma (melted rock that is underground) was once full of gas, and the pumice rock still has a bunch of tiny holes or vesicles in it, and it is really light weight. There have been tests done on pumice and some of it has been found to still float after a year and a half in the water. That’s amazing!

There is a bunch of pumice all over the beach here and it’s all most likely from the 1912 eruption of Novarupta volcano. We got pink pumice. We got white pumice. We got brown, orange, yellow, white and gray pumice. And most exciting of all – hold on to your hats, folks – we have banded pumice. Woo Hoo!!! Banded pumice gets igneous geology-types all worked up. It is a combination of several different types of magmas – mainly rhyolite, andesite, and dacite, depending on how much silica is involved – and geologists have been working for years to figure out just how those magmas were mixed underground before they erupted in the 1912 volcano for which Katmai is so famous.

Banded Pumice

Glaciers retreated from this particular area of the Alaska Peninsula around 10,000 years ago, leaving us as evidence of their presence what are referred to as “glacial erratics.” These are often boulder-sized rocks that were carried along by the glacial ice as it advanced and moved far from their mountains of origin, and dropped wherever the glacier melted. Granite boulders of varying sizes can be seen on the shores of Naknek Lake, having been carried there from the Aleutian Range, many miles distant.

Glacial erratics

There is also a nice outcrop along the beach of fossilized leaves and petrified wood from the early Jurassic (198-177 million years ago) Talkeetna Formation. This rock formation, which includes shallow marine (ocean) sedimentary rocks, was once part of a volcanic arc much as the Aleutian subduction zone is today (where the Pacific plate is diving or subducting beneath the North American plate along southern Alaska and the Aleutian Islands). The rock outcrops can be traced for over 900 miles, from Katmai north to Cook Inlet near Anchorage, then east through the Talkeetna Mountains and on to the Copper River basin.

Leaf fossil in mudstone

Sunday I am going back to the Valley of Ten Thousand Smokes for the day. The tours are run by Brooks Lodge but a park ranger goes along as interpretive guide on each tour. The owner of the Lodge told us that since the tour isn’t full (so early in the season) anyone from the Park who wanted to go was welcome. Of course I immediately volunteered! It is my day off and I’m not the guide, so I don’t have to go in uniform but can relax and enjoy the geology. It is a pretty cool date, too – June 6, 2010 is the 98th anniversary of the explosion of Novarupta.

2 comments:

  1. Ms Glacial Erratic,

    I hope ya'll had a happy 98th anniversary party for Novorupta.
    Could it be Dumping Mountain got it's name from people dumping banded pumice into the lake? Is it really that slow this time of year?
    That is cool Brooks Lodge takes you along on their tour - what would it cost the out-of- towner for the same trip?
    WEATHER FLASH - just in case you are missing the last vestiges of spring here in Southern Utah - Lake Powell 103*, Saint George 107* and finally Mesquite (Beaver Dam Mountains) 113* !!
    That's right.....

    Look on the horizon - the cruise ships are arriving.

    Your Tour Director

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  2. We don't get cruise ships here. People come in on float planes.
    I think it's entirely too early for those temps to be getting to high!
    It costs $96/person to go on the Valley tour, which includes a lunch. The Park guides bring their own lunch or can purchase one from the lodge.
    I made a typographical correction to the name of the mountain - it's Dumpling. Nothing to do with the pumice, though.
    Yeah, sometimes it's a stretch to find something to do on my free time. Good thing I like to read so much!
    We sang Happy Birthday Novarupta!

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