Re: Sauropods in wet versus dry environments... a tip of the hatto some past ...

[Dinogeorge@aol.com]

In a message dated 1/16/02 10:00:15 PM Pacific Standard Time, 
dinotracker@earthlink.net writes:

<< With each step, the animal is compressing the hard
 substrate at the grain level, driving the grains closer together for some
 respectable depth >>

You might be surprised to learn that when something makes a track, the 
substrate grains are not driven closer together but are driven apart. This is 
because the grains are already maximally closely packed and cannot be driven 
closer by the action of the foot. What happens is the grains are driven 
apart, then rapidly fall back into a new maximally close-packed configuration 
after the pressure of the foot is released. The extra space required by the 
grains driven apart comes from the volume around the foot where the substrate 
squishes out. For example, when you walk on wet sand, you will notice that 
the sand dries momentarily beneath your feet. This happens because the sand 
grains are moved apart, allowing the water in the immediate vicinity to 
escape into the widened interstices between the grains. In due time the 
grains fall back together and the water is squeezed back out again.