And Now for Something Completely Different
This has been a tumultuous week, and today my city has been struck with a debilitating heat wave. Enough of disaster, enough of politics, enough of everything. Today I rummaged around in my photo collection and added a few new items to the slickenside gallery. I think I'll do some more rummaging.Slickenside in limestone Geology Guide photo
Aftershocks and Rumors of Aftershocks
There is a line of thought among earthquake researchers that maybe, if you back away far enough, the earthquakes in a large tectonic province or even the whole planet can be analyzed as if they were a great self-generating aftershock series. That underlies some interesting basic research tied to earthquake prediction, but it doesn't provide the planners and responders of today any useful information.
Inevitable Quake Rumors Arise in China
Let me say first that no one predicts earthquakes today in government or academia. China tried for a while starting in the 1960s. Offices opened all over the country to collect stories of unusual animal behavior, natural phenomena and seismic signals. In 1975 an earthquake warning issued to the city of Haicheng was actually followed by an earthquake, and many lives were saved. That is the only significant time the system has worked, and today the general scientific opinion is that it was coincidence. The Chinese model may be flawed by its cultural/political origin at the height of Maoism, the apotheosis of the proletariat. Large networks of amateur observers were relatively easy to establish, and the prediction algorithm relied on folk traditions. But human sensory observations are notoriously unreliable, and the folk traditions do not hold up against actual data.
The eruption of rumor in the Chinese blogs surely matches what everyone on the street is saying, the same things people everywhere have always said. The history of amateur observation probably adds nuance to the Chinese response. But it's a good inoculation to read the Chinese expressions of panicked thinking now, in hopes that we will be less susceptible when our turn comes in our own lands.
It is literally human nature to turn events into stories imbued with meaning. People who claim to have open minds are often the fastest to shut them down, grasping at an explanation and clinging to it against all evidence. One of the hardest things a scientist can do is resist human nature and remain open to new explanations, but that's what they train for.
M 7.8 Earthquake in Sichuan, China
Tidal Wave or Not?
On the one hand, the results of tsunamis and storm surges are the same for human purposes and probably the same in the sedimentary record. When we look for ancient tsunamis, the historical record is ambiguous. Some of history's most deadly tsunamis might have been storm surges. History mentions very deadly "tidal waves" along the South Asian coast, comparable to what we're seeing in Myanmar, and for planning purposes we need to beware both earthquakes and storms.
On the other hand, for geology the two causes must be distinguished, if possible. In some places, such as the American Gulf coast, there are no earthquakes, and the prehistoric hurricane record can be deciphered by experts in paleotempestology. But if the Myanmar cyclone had happened a thousand years ago, could we tell from the sediments what had happened? Hard to say. Without sure signs of earthquake such as sand blows or suggestive signs like mud volcanoes, we're stuck.
But probably arguing about "tidal waves" versus "tsunamis" is immaterial, just as it is when the press talks about the "Richter scale" for earthquakes. The important thing is that geologists get to explain Earth hazards to the public.
More on Cores
Earth Science in Space
I don't let geology keep me Earthbound, not when so much of interest to geologists happens above the ground and out in the rest of the universe. I've written (and newly updated) a seven-part series of articles on various atmospheric and space-related topics, including sprites, stardust and cosmic impacts. It starts with the Sun.The Sun in ultraviolet light NASA image
Big Blowup at Chaitén
Not much is known yet scientifically. Another recent eruption in southern Chile, that of Cerro Hudson in 1991, released a large quantity of fluoride and sulfide gases into the stratosphere that subsequently contributed to a large Antarctic ozone hole. Chaitén is about 250 km north of Hudson and 150 km south of Puerto Montt, the end of the road.
Follow the official news from the Chilean geologic agency SERNAGEOMIN. If your Spanish isn't good, Google's translation service does a decent enough job. The agency is conducting daily overflights and is deploying a local seismic network.
The Ultimate Webcam
Dendrites
They look like fossils, but dendrites are purely mineral growths whose fractal, arborescent habit gives them an organic appearance. Instead, they're generally made of psilomelane or pyrite. Museum specimens and expensive moss agates can be spectacular, but if you keep your eyes open you'll see dendrites in humbler guise, like I did in this sandstone boulder at the Dinosaur Ridge headquarters building.Dendrite Geology Guide photo

