Musher: You must have metric dirt.
Most people don’t realize how big a cubic foot is. A plastic “milk crate” is a little shy of a cubic foot. Fill one completely full of dirt one time and pick it up.
We all know that water is “a pint a pound” or 8 pounds to the gallon. A cubic foot of water is 7.5 gallons. So a cubic foot of water weighs about 60 pounds, not surprising then that a cubic foot of dry
dirt weighs 75 lbs.
That “dry” part is important too. Nobody ever talks about the buoyancy factor. Everything you throw in the water wants to float -- even a rock. The weight of the object is lessened by the amount of water it displaces. Let’s say you took that dry
dirt, packaged it very tightly in a plastic bag (removing all the air), and threw it in the water. That 75 lb chunk of dirt, will displace 7.5 gallons of water (60 lbs). It really only weighs 15 pounds, underwater.
However, most any trapper using dirt for an anchor is going to be using wet or damp earth to fill the bag. This is much heavier than dry dirt. Of course things like rocks and steel are even more dense (displace less water) than dirt.