Thursday, November 1, 2007

The Seismic Survey

Hope everyone had a good Halloween and enjoyed a chocolate bar for me. I wanted to show you what “Little Andrill” has been up to lately and give you a math problem to solve. In my blog while waiting for the weather to clear, Marv described the seismic survey process. I have some photos to share with you now that we’ve started the survey.
The first step is to get a good hole to drop the air cannon into so that it is under the surface of the ocean under the sea ice under us. Kyle Webster is our driller. He likes to call himself the “Drilling Superintendent”. He makes great holes for us.

And sometimes enjoys his free time. Note: this photo was taken while we were all having a lunch break.

After we have a good hole to work with, the air cannon is lowered to eight meters below the surface and fired four times with 2,000 psi (pounds per square inch) of pressure.

The geophones that trail behind the airgun trailer (known as the Thunder Sled) for one mile record the vibrations from the strata under the sea floor and are recorded by computer equipment.
Marv and Ross will look at the data for quite some time after we complete the survey to determine the best location for a future core drilling project. Ross is hoping to get an area of large depositional Holocene records that will tell us more about the history of the Mackay Glacier.
Here’s the math question part: while we were completing our work yesterday, some of us were wondering just how much ice was coming out of the holes being drilled. Bob, my fellow ARISE Educator tried to figure out the answer using snow and finger rather than pencil and paper.

Feel free to use a calculator if you need to. What is the volume of the hole that measures 13 inches in diameter and is averaging 2.2 meters deep? (Sorry, yes you will have to do a metric conversion, but I’m sure you can look it up on Wikipedia or somewhere else) By the way, don’t use the numbers that Bob is using. He mixed up the units and didn’t get the right answer the first time. And here’s a photo of me in front of our kitchen tent just so my family doesn’t forget what I look like.
[Note: Julia is currently on the Seismic Survey. Are you wondering how she is able to blog without internet access? CDs with her blog text and pictures mysteriously arrive at Crary Lab every now and then. What is happening is that helicopter pilots that are passing by the survey camp or are ferrying some equipment out there stop at the camp, and Julia hands them a CD that they later drop off here at Crary Lab. We then post her blog for her]

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