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5 August, 2000

August 5 , 2000

Matanuska Glacier, Alaska

There was an interesting event that occurred during the drilling today. The new drill sites are located on the low flat ice sheet near the Mammoth Vents. This ice sheet is probably no more than three or four feet above the “lake” that is produced by these vents. In both holes that were bored today geysers of water maybe a foot high shot up through the holes. I suppose that given the location near the vents that it should have been anticipated but it caught everyone off guard. Some people who weren’t there when it happened made a special trip out to have a look. Ben and I are now curious about whether or not our dye would come out this “man-made vent”. It will be intetresting to see if frazil ice terraces form around them.

I had quite a bit of free time today and spent some time hiking up above the seracs by the glacial lake. On my way back I stopped to look at several moulins. It seems like something really odd is going on. The moulins all seem to be backed up like they’re clogged somehow. A couple of them even had pools just a couple feet below the ice rim. It’s odd because the melting of the ice doesn’t seem to be as high as it was a few weeks ago. The surface runoff into these moulins is not nearly as high as it had been. A number of people have remarked that it’s been an unusual melt season this year and I’ve heard a local resident complain about the lack of the usual summer weather they are accustomed to. Maybe something unique will happen.

During the summer melt season the rivers that drain glaciers experience a drastic rise in water level. The levels can change quite a bit during a given twenty-four hour period as well as from day to day. The valleys below a glacier are broad and very flat and the streams produce numerous gravel bars. After several warm sunny days the streams rise up and occasionally over these gravel bars and new ones are produced as the water recedes once again. The result is something called a braided river. There is an aerial photo of the drainage just below the Matanuska Glacier in my July 26 journal. In that picture you get a good idea of why they have that name. Because these rivers are so wide they can handle a significant rise in water volume and yet not increase in height very much. However, with the higher levels comes a whole new appearance to the resulting gravel bars. There are several whitewater rafting companies that capitalize on the summer flow. It appears to be a nice safe river for family trips with long standing wave trains that are big enough to get occupants wet and provide a fun ride but small enough to keep everyone in the raft. All the outfitters provide dry suits to keep the parcticipants protected from the icy splashes. During the winter there is very little water flowing in these streams. What does flow is from groundwater sources.

We’re still waiting for the dye to get here from the CRREL office in Anchorage. As soon as it arrives we will be resuming our dye tests. I’m anxious to get them started again especially now with our “man made vents” gushing forth.

Marvin Giesting

Isaac Larsen prepares to hitch the drill rig as water gushes from the new hole.

This is the same area of braided river as in the aerial photo from the July 26 journal. As you can see it is very wide and flat.

This is the same moulin that we've been dumping our dye into recently. Compare this picture to the one on July 27. Something's up!

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