Let's see if we can do in one day's time what it took Nature several million years to do.

Your teacher will provide a gallon jar, half full of water. Taking turns, the students can add handfuls of sand, gravel, soil, powdered clay, iron filings (be careful!), maybe some tiny shells and a dead bug or two.

The mixture represents materials that might be deposited by a river in an ocean, sea, or lake.

Shake the jar, then set it on a table where it will not be disturbed. Look at the jar (from the side; not from the top) several times during the day. Don't touch it! Nature
sometimes let silt deposits stay undisturbed for centuries. Surely we can do it for a day!

When the water is clear, look at it very carefully. You will see that the stuff we put inside has formed layers. Isn't that exciting? How do you think Nature decided which
substances should be in which layer?

The settling action is analogous (say, "ann-AL-oh-guss;" it means "sort of like") to that of natural materials being added to older layers of material year after year. The tiny
shell and dead bugs can be anywhere, but they probably will not be on the bottom. [Incidentally, the most valued pieces of a stone called "amber" are those which have a dead bug in them! Yuck!]

Many mineral deposits are thought to have been formed in this way.

This writer has a fossil sea snail that has several layers of different-colored silts in it, and a layer of crystals on the top. It is probably two hundred fifty million years old!
When that creature first died, it probably didn't have anything in its' shell that is interesting, except for its own body.