Kenneth Terry, age 11, of Hinden, W.Va for his question:

What are Archean rocks?

This takes us way, way back to the babyhood of our planet. The story of the earth is written in the rocky layers of the crust which forms the continents and the seabeds. In most places, the olde7t layers are the deepest and their story dates back some 4,000 million years. This, we think, is when the young planet cooled from a molten state and began to form its solid crust.

The word archean has an ancient sound and the archean rocks are old indeed. They tell the story of the first half of the lifetime of our solid little planet, for they were the first firm rocks to form from Its molten fires. The archean rocks cover a period of time tech began some 4,000 million years ago and ended some 2,000 million years ago.

The face of the earth is eternally changing. During the long ages, mountains rise and fall, seas slop over the land masses and recede, ice ages come and go. Old layers of rocks constantly are being changed and new layers constantly are being made. The changes which occurred in the first 2,000 million years of the earths history were quite as extensive as those which have occurred since.

The first part of the story, however, is harder to read for the oldest rocks are usually the deepest rocks and for eons of time they have suffered the crushing pressure of the rocks above them. These gnarled and ancient layers are the archean or pre cambrian rocks,. In some places we must dig a mile or more to reach them. In Grand Canyon, the busy Colorado river has cut down to the archean level. North of the Great Lakes, a vast shield of archean rocks has been brought to light by the wearing away of an ancient mountain system. These older than old rocks tell us that six huge mountain ranges as high as the Himalayas rose up and wore away during pre cambrian days.There were ice ages in those far off times, regions of desert and volcanoes.

Archean rocks are metamorphic minerals, changed from their original states by pressure, volcanic fire and watery sediments. They include shale’s and dense gneisses, schists, dolomites and ancient sandstones. Certain archean rocks are rich ores of iron and copper, nickel and lead, cobalt and zinc, mica and silver.

There is evidence in the archean rocks that life existed even in those far off times. The archean deposits of Glacier National Park in Montana record ancient seaweeds. There are other records of archean sponges, of wormy animals and one ..celled creatures that lived 2,000 or more million years ago.