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13 January, 2003

Casing Crisis

Today the teams rotated somewhat and I set off to the lake to help with coring, while others set off collecting rocks and minerals. Lake Bonney is an unusual lake in that there is a layer of halite (NaCl or table salt) on the bottom of the lake. This layer does not exist in the other lakes in Tayor Valley. So how did it end up in this lake in the middle of the valley? It is estimated that the halite is about 10-20cm thick (4 -8 inches). Part of Jake's graduate work is to research why this halite layer is present, and to study what is beneath it.

The ice on Lake Bonney is 5-6 meters (16-19 feet) thick. Then there is water beneath that until you reach the lake floor at 39 meters (127 feet). On the bottom is the layer of halite and under that is dihydrohalite (NaCl 1/2 H20) that has a consistency similar to toothpaste. We want to find out how thick that layer is and what is under it.

Our first step was to lower the corer through the casing without the piston inserted. Our goal was not to core, but to break through the halite by hammering the core barrel head into the halite. We lowered the corer and began to slowly hammer by raising and dropping the 20kg hammer weight. Disappointingly, as soon as we began hammering, the casing began to lower into the hole, an indication that the casing had either bent at a joint or even coming apart. This was very frustrating for the team because we had fed cable through the entire center of the casing and up the outside to help secure it. Needless to say this method was not going to work as anticipated, so we spent a good portion of our day removing each piece of casing. It had been difficult for the team to build the 39 meters of casing yesterday, and today was equally hard removing the 13 individual pipes. We would be forced to try to break through the halite without the assistance provided by casing, thus increasing the risk of bending our extension poles, the oblong rod, or the core barrel, but this would be a job for tomorrow.

We came off the ice and into the jamesway to warm up. It was nice to enter the hut to be greeted by our friends from F6 camp who are studying streams and remapping the area (LTER group).

This is a piece of halite removed from Lake Bonney.

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