A very hard layer of rock can form a temporary base level, until it is cut through.

A layer of white or gray mold will form on top.

These layers may have formed when the whole area was a giant lake.

At the same time, the bottom layer forms a small sac.

The very top layers of the Earth form a thin skin, the crust, which is only a few miles thick.

Programmed to strip out all the blue, the computer can then join the layers to form a single shot.

By now all the booths were full, and a second layer was forming around the bar.

Only the inner layer had formed when the lighter struck.

Another layer formed above, high in the stratosphere, beginning to spread.

In a huge quiet room, defined stagnant layers could form.