These rocks formed between 363 and 325 million years ago.

The rocks formed a low, broken wall into the river.

These rocks formed in the area approximately 320 million years ago.

He came to a place where steep rocks formed the side of the river.

Many new rock and alternative groups/bands form during the early years of this decade.

With others the rock forms last and cracks easily when you stick your hand through it.

Other sedimentary rock in the area formed more recently, around 20 million years ago.

Beneath it, another rock formed a ledge five feet below them.

Magnetite has been very important in understanding the conditions under which rocks form.

Rock can form layers in a variety of ways.