Tuesday December 10, 2013
I'm in the middle of a week at the Fall Meeting of the American Geophysical Union, in San Francisco. This is typically a whirl of talks, posters, refreshment breaks (coffee in the morning, beer in the afternoon) and throngs of geoscientists. I typically don't cover the meeting like a journalist does, although I share the press room with them. A lot of what I seek out is background stuff that I hope is ahead of the cutting edgeat least, it's ahead of my cutting edge. A talk I saw yesterday was not one of those.
Manny Gabet, teaches at San Jose State University, has been studying the odd landscape features known as mima ("meema") mounds. They're piles of dirt, meter or two high, and range in area from dinner-table to living-room size. They occur bunched up together in big groups, and are widespread in the American West. Gabet cited two special facts about them: they're found where the winter rains regularly saturate the ground, and they're occupied by pocket gophers, one on each mound, with the unusual habit of pushing the dirt from their burrows uphill. He made a computer model of a bunch of gophers and set them loose on a flat computer landscape, showing that their behavior, over several centuries, turned the ground into fields of mima mounds.
The advantage of a mound is that it sits above the winter rains, making large areas of marginal land inhabitable for gophers. Gabet told us that by his reckoning, mima mounds are the largest set of animal-made structures on Earthother than our own, of course. It intrigues me that a single change in behavior brought this aboutpushing dirt uphill instead of downhill. That probably arose from a very small genetic change, one that doesn't make a difference east of the Mississippi, where mima mounds aren't found.
Sunday December 8, 2013
Geology gave the world the gift of immense time: not just the measly millennia counted by old civilizations, but millions of years and billions of years, more years than anyone could count. It made even the absurdly long sacred chronologies of the Hindus look reasonable. And as we explored all that time, we figured out how to organize it into structures of time, hierarchies of time periods with, eventually, actual dates assigned to them. That's what this week's "Who Wants to Be a Geo-Whiz?" quiz is about: geologic time. Now don't dawdle, you've only got a week.
Saturday December 7, 2013
This message is for the thousands of geoscientists arriving for the coming week's Fall Meeting of the American Geophysical Union
. If you're going to San Francisco, be sure to wear . . . some decent walking shoes. Because the city is full of geological attractions. I've got a fair sampling of them in this photo-tour
. Some of them might be unexpected; for instance, the Japanese Tea Garden in Golden Gate Park displays some of the different local rock types with plantings and decorations that complement them. There are no signs pointing this out, just little pleasures awaiting your tranquil, enlightened gaze.
San Francisco geology
More California geology
Visit San Francisco
Franciscan basalt Geology Guide photo
Wednesday December 4, 2013
A brief remark at a talk in October led me to a clever bit of science that offered a way through the paleomagnetic mirror problem. By that I mean the ambiguity that results when a moving continent heads toward the equator. The paleomagnetic record shows it reaching the equator, then moving closer to the magnetic polebut in which hemisphere? Just from magnetic evidence, there's no way to decide whether the continent plowed straight onward into the opposite hemisphere or backed off and stayed on its original side of the line. The solution had to do with the Coriolis force, the only way we have to tell the left-handed hemisphere from the right-handed hemisphere. So far this method has been useful only once, but I was pleased that a method existed at all. Details in this new article, "Disambiguating the Paleomagnetic Record."