Tuesday April 22, 2014
I love Earth Day as much as the next guy, but I have little use for it. To the geologist, every day is Earth Day, and the rest of the crowd seems to be singing from a different hymnal. So let me offer for your delectation three different essays about the occasion:
- In "Getting Down to Earth Day," I urge that more geoscience be celebrated in addition to the water and the wildlife.
- In "A Better Kind of Earth Day," I contemplate ways to observe the occasion with more weight and bite in light of our true relationship with this lovely planet.
- In "Earth Day? How About Earth Life?" I ask us all to get to work on the distant future, because it's coming fast and all hands will be needed.
Enjoy Earth Day 2014.
Sunday April 20, 2014
Over 200 years ago, we began to glimpse the outlines of the great engine that sculpts and maintains the Earth as we know and love it. It took a century and a half to come up with a paradigma body of theory and worldviewthat we could sink our teeth into: plate tectonics. Today the general public is familiar with the basics of plates. But this quiz gets into the deep details that only a Geo-Whiz has mastered. Could you be one? Give the quiz a try.
Saturday April 19, 2014
In geology, the rocks have a way of messing with our pretty schemes. One instance I'm thinking of involves the base of the geologic time scale. The Earth itself is about 4.5 billion years old--but the time scale starts at the base of the Archean Eon with a time unit called the Eoarchean Era, running from 4.0 billion years ago (4 Ga) to 3.6 Ga. Like most of the Precambrian time periods (and unlike the more familiar Phanerozoic time periods), the Eoarchean is based on arbitrary numbers rather than notable geologic events.
When this part of the time scale was put together, we figured, from long experience, that there weren't any rocks older than 4 Ga. So much for experience: now we have rocks in hand that are older than the official time scale, and some zircon crystals that are reliably dated at 4.4 Ga. Today, Hadean time is no longer a matter of conjecture. So I hope someone is thinking about setting up signposts in deep time for the Hadean Eon. I suggest the Paleohadean for 4.5 to 4.4 Ga, the Mesohadean for 4.4 to 4.2 Ga, and the Neohadean for 4.2 to 4.0 Ga.
Here's an oddity: in the Cenozoic Era, the Paleocene Epoch comes before the Eocene, but in the Archean the Eoarchean comes before the Paleoarchean. Why is that?
Friday April 18, 2014
It was 18 April 1906, 5:12 local time when the rumbling began. (Today that hour would be 6:12, a quarter-hour before sunup.) More than a full minute later, the shaking was still going on, and hundreds, maybe thousands of San Francisco's buildings had fallen, broken or caught fire. With the water supply rendered useless, fire raged over the city for three days and left half its people homeless. And that was only the beginning of the story of the great San Francisco earthquake, 108 years ago today. The legend lives on, even if no one alive can remember that day, because artifacts of the time still stand in Baghdad-by-the-Bay. This fire hydrant was connected to a cistern that continued to supply water near Mission Dolores and saved the neighborhood. Ever since that day, the hydrant has been painted gold. Folklore and ceremony are good ways to keep awareness alive.
If you've ever given serious thought to how earthquakes would affect where you live, the 1906 quake is as timely a lesson as ever, and there are several good books I can recommendand one to steer away from.
The miracle fireplug Geology Guide photo