After my post yesterday about the frozen swamp I heard from two engineers and one scientist. Two common threads ran through all three responses: 1. There is not enough information in the story to reach a definitive conclusion; and 2. Even so, the veracity of the story is highly dubious.
One engineer said the missing information which needs to be considered includes the air temperature during the previous week, the temperature of the rocks and how long it took them to sink when they were thrown into the swamp, the temperature of the water before the 30 degree drop, the temperature of the surrounding soil, and the number and size of the wheels on the wagon carrying the monument.
The scientist said that we need to consider the mud/water/vegetation ratios in the swamp.
The other engineer, in agreement with the above considerations, nevertheless suggested that conservative assumptions could be made on many of these issues and a calculation could be applied. His opinion is that whether the “frozen solid” assertion in the story refers to water or to muddy muck, the rate for freezing for either substance is similar enough to determine times and temperatures “within the ballpark.”
He sent a link to an equation from the Encyclopedia Britannica that models the rate of freezing of ice on water. Applying this equation, he provided the following information using the Fahrenheit scale:
If the temperature started out at 33 degrees (so the swamp was not yet frozen) and dropped to zero degrees, after 12 hours at zero degrees there would be 1.66 inches of ice on the swamp.
If the temperature was zero degrees and we needed to have 8 inches of ice on the swamp (a reasonable depth to hide the rocks that were thrown in) it would take 93 hours (almost 4 days) to freeze to that depth.
If we only had 12 hours for 8 inches of ice to form, to accomplish that the temperature would have to be 215 degrees below zero.
Furthermore, regarding ice and the load it can bear, this engineer reported that according to the State of Minnesota, a medium-sized pick-up truck needs 12 to 15 inches of ice to bear its weight safely, so the 1.66 inches that could reasonably be expected to form on the swamp overnight at zero degrees would certainly not be enough to hold 40 tons and 22 horses as they “passed over the swamp without difficulty.”