Probling the Depths of Crystal Lake

Crystal Lake was being mapped by the Illinois State Geological Survey the Thursday before last. (The one seen here is from 1957. It shows ten-foot intervals down to deeper than 40 feet.)

I asked what the state agency was doing and here’s the reply I received from Illinois Geologic Survey geologist Brandon Curry:

Hi Cal,

Thank you for your phone message.

The boat was out in the lake on Thursday doing geophysical surveys in an attempt to image the lake’s bottom sediment.

We used two techniques and had three objectives; two of the three will likely be successful, but the third may not work out as well.

One product will be an extremely accurate bathymetric map (which I think you mentioned in your message).

A bathymetric map shows lines of equal elevation of the lake’s sediment, and should be accurate to within a foot or so. There are earlier bathymetric maps available, but this one should be the best one done to date.

The other product is an Echosounder image… it does two things… it creates a detailed surface reflection, and also provides some data on the shallow “acoustic properties” of the surficial sediment. The combination of the two should result in an interesting map from which we should be able to classify the lake bottom sediment, and perhaps, aquatic vegetation, in addition to subterranean springs.

The third product will probably take the longest to produce, and is the product of seismic reflection.

The useful product from this is a deeper acoustic cross section of the lake sediment. This technique is hindered by methane bubble(s) in the sediment.

Preliminary results suggest that very little penetration (1 -2 meters) was achieved using this technique, which is too bad, but we’ll have to wait and see.

Each of these techniques needs a lot of computer processing time. Our consultant, Dr. Nigel Wattrus (University of Minnesota – Duluth), says that it will take about a month to process the data. I haven’t talked to Nigel yet, but I would think that the bathymetric map should be done fairly soon… ostensibly, it’s the easiest to process.

I asked for something that would give an idea of what the mapping might provide and was sent the map of Crystal Lake’s 1957 depths you see in this article:


Sure thing! Attached is a jpg of a figure I used for a proposal to do studies of climate change based on the fossil record. The proposal was sent to the University of Illinois Research Board, and was, by the way, not funded.

Using some money from old grants and limited support from the ISGS, I will be working on the part of the record that should tell us about paleoclimate from about 7,500 to 9,000 years ago (why this time frame? It’s when we know Illinois went from moist to dry).

I will need more funding in a while to continue my study as I go up the geological column. I would imagine that there would be interest in a study of drought frequency (climatic) conditions over the past 2,000 years.

Can you think of local funding agencies that would likely endorse such a project?

The asking price… about $15,000. The study could be done in one year.

Agencies such as NSF don’t generally fund projects that are that limited in scope geographically. Please don’t be offended by me pouncing on you this way… I’m just testing the waters.

And, as a matter of fact, I can think of who might be interested in rainfall records.

How about the villages that have water bans in effect? Might not they be helped by knowing what happened in the past, so they can adapt in the future?

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