Geology Maps

By: Charles Bowen Decades ago, as a college student trying to fulfill a physical science requirement, I wandered into a geology class with something less than great expectations. But I surprised myself. I got hooked on a big story, perhaps the biggest story: How the
planet Earth came to be.

For several years after that, I became a devoted -- not to say obsessed -- rock hound. I even got my father-in-law involved and we spent some time together bonding and trolling for Trilobytes in the fertile neighborhood riverbeds.

Ever since then, the years I spent in amateur geology have added a dimension when I travel. Whether looking down from airplanes or examining the enormous cross-section created along the sides of our ever-expanding interstate highway system, I'm still telling time with the rocks.

And sometimes boring my fellow travelers.

"Whoa! See that? It's a sliver of the Devonian period. We don't have that back home. That's, like, 400 million years ago, when the first forests appeared and the first vertebrates colonized the land. North America was attached to Europe then, around the equator..."

Yes, you're right. A respectful silence does greet many of my pronouncements on the subject.

And through the Web I've found not only like minds but also the mother lode of geology information. A new site called "A Tapestry of Time and Terrain" from the U.S. Geological Survey brings together the comprehensive geological and topographical maps of the United States.

Billed as "a helpful teaching tool" -- and, of course, it is -- it also is a site for fun surfing for anyone who is just curious about the story told beneath our feet.

Reached at http://tapestry.usgs.gov, the site rolls out what those poets at the USGS calls a "digital tapestry (that) outlines the geologic story of continental collision and break-up, mountain-building, river erosion and deposition, ice-cap glaciation, volcanism, and other events and processes that have shaped the region over the last 2.6 billion years."

On your first visit, you might want to start by watching the Quick-Time film that shows the merging of the two maps, along with a brief description of how each individual map portrays the United States.

Within the features description section of the site, you can interact with a clickable map surface that details the prominent features of the United States, such as the Driftless Area of Southwestern Wisconsin and the Olympic Peninsula in the state of Washington.

For real learning, click on the assorted sections of the interactive map legend, which will produce descriptions of the different eras, such as Paleozoic or the Precambrian. You may be surprised just how long some of those local rocks have been lying around.

For other considerations in using Tapestry of Time and Terrain in your work:

1. For a closer look at geological data for your specific region, note that the Boundaries option on the introductory screen brings you to a clickable state-boundary map. Select it and you can explore the geological terrain for any U.S. state and click a link to reach that state's own geological survey.

2. Also in the Boundaries section is an option to view the material through an interactive map of "physiographic regions." This can help the serious student explore the broad-scale subdivisions of data based on terrain texture, rock type and geologic structure and history. For instance, if you're interested in the Appalachian Plateaus, you can use this map for more information the Mohawk section, the Catskills, New York, the Allegheny, Kanawha and Cumberland Mountains.

3. If you write about this feature in your news columns or Internet features, you might want to point out the site's new puzzle feature which enables kids to work large geological jigsaws on the screen.

---
You can read the last 20 "Reporter's Digital How-to" columns on our index page. Subscribers may access previous columns from our archives.