June 3, 2010

Happy Birthday, James Hutton

Born this day in 1726, in Edinburgh, Scotland, James Hutton grew up to be the father of modern geology.

Hutton's list of accomplishments include being a physician, naturalist, chemist, and experimental farmer as well as a geologist. His contributions to geology include the idea that the earth's rocks were created from materials laid down in early oceans—dirt and sand and the shells and bones of living creatures—and that these rocks were later uplifted into their current place above sea level.

He suggested that this rock-building process has gone on for a long time, and that today's rocks are continuing to erode and wash out to sea, creating the rocks of the future.

With this ongoing process of rock formation, Hutton made the case for the Earth being much, much older than most people had suspected.

Hutton was a famously bad writer.

Want a sample? Here's one:

“The world which we inhabit is composed of the materials, not of the earth which was the immediate predecessor of the present, but of the earth which, in ascending from the present, we consider as the third, and which had preceded the land that was above the surface of the sea, while our present land was yet beneath the water of the ocean.”

Yet he is credited with a nice turn of phrase here:

"(In geology) we find no vestige of a beginning—no prospect of an end."

Before Hutton...

... most people had supposed that the bedrock beneath our feet had been around since the beginning of the world, or perhaps since a single enormous flood a few thousand years ago.

But Hutton's analysis of the composition of sedimentary rocks showed that there had been at least several cycles of erosion - rock formation - uplift, and possibly many, many cycles.

Hutton proposed that Earth was hot in its interior, and that the planet was millions rather than thousands of years old. (He was right about Earth's interior being hot, but our planet's age actually numbers in the billions of years. Still, Hutton's estimate was a huge improvement over earlier ideas.)

The Rock Cycle

Hutton's discovery about the rock cycle largely deals with sedimentary rocks and metamorphic rocks. Sedimentary rocks are created when layers of dirt, sand, and remnants of life are pushed down over the years into hard rocks. Metamorphic rocks are usually sedimentary rocks that have been changed by extreme heat or pressure.

We can often see layers
in sedimentary rocks.

• Here is a cartoon-illustrated explanation of the rock cycle.
  

• Here are animated diagrams about how various kinds of rocks form: this is a simple version, and this is a more detailed version with lots of buttons to click to see more animations and to learn more.

• Here is a “recipe” for a quartz sandstone outcrop (a kind of sedimentary rock landform).

• Here is an activity that will help you see how sedimentary rocks form.