Article Published on geology.com

My article "How Old Is The Grand Canyon?" went live this morning on the web at geology.com. You can jump right to it here. Thanks to Michael Conway of the Arizona Geological Survey for connecting me with Hobart King who operates the site.

The history of the Grand Canyon is large and complicated but there is nothing I enjoy more than making its story at least a bit more understandable and accessible to those not well versed in geo-speak. Hopefully, this article will do just that. Enjoy it and share with your friends.

Book Review: North Pole South Pole

I rarely do book reviews on this site, it being more oriented towards field explorations in the southwest. But I can not count how many times I have been leading a trip and someone asks me detailed questions about the earth's magnetic field. There is just something about the earth's magnetism that is ... well, magnetic to some folks. They want to know how it all works.

Maybe it's because all of us used to use magnets in the dirt as children to gather iron filings. That was cool. Or maybe it's the way a compass intrigues us - magnets always point north no matter where we go. (Although on my first trip to the South Pole in 1986, we pulled out a compass and watched the dial point down against the bottom of the compass as it tried to point north from there). The next time someone asks me about the earth's magnetism, I'll just tell them about Gillian Turner's new book, "North Pole South Pole", published by Awa Press (New Zealand) and The Experiment (New York). This small but handy book contains a history of our knowledge about magnetism, and the scientists who have studied it through a long span of time.

As most geologists will know, the earth's magnetic field sometimes switches such that what is now magnetic north reverses to the other side of the planet. This last happened about 780,000 years ago and many scientists wonder what a magnetic reversal would "look like" if we lived through one. Do species go extinct during these events or become confused when they migrate? How long do reversals last? Readers of this book have to wade through gobs of history concerning past study and understanding of the magnetic force to find these answers - the book deals mostly with a chronology of this understanding. I wish there would have been a table in the book where all of the "facts" concerning the magnetic force were readily available. As such, this is a book that will likely find favor only to other scientists and historians of science.

But I still found the reading worthwhile. Turner is a very easy-to-read writer who crafts her sentences well, with stories that flow nicely. Most of us received what little knowledge we have of the magnetic field in grade school and a book like this has such a depth of information about the important milestones in the field that you are sure to learn much from it. But you'd have to be interested in the topic in a big way to keep slogging through all of that history. Someone could probably write another book for non-scientists on this topic that would be more approachable, but if you are a scientist and want to know about the history of magnetic studies, this is your book.

I learned many things from Turner but the most fascinating was that the strength of the earth's magnetic field has dropped 15% in only the last 200 years. Could this suggest that a magnetic reversal is underway? Perhaps we will get a chance after all to live through one of these!

An East Africa Volcano Like No Other!

Many friends have been e-mailing me about this link from the Boston Globe. If you have not yet seen these pictures of a crater located along the East African Rift Valley, you must see them now. Follow the link here.