two earthquakes from San Juan Bautista that took place last night just five minutes apart. In the record above you can see the 3.6 magnitude foreshock on the left side, and the larger 4.2 magnitude quake in the center. This seismogram nicely illustrates the vast difference in the size of the two quakes. In terms of energy release, a magnitude 4 quake is about 32 times more powerful than a magnitude 3. So the 4.2 quake is many times larger than the 3.6 (can a seismologist out there do the calculation?), which is obvious from the graph above. The 4.2 was not just a little bit bigger, it was huge in comparison.
I isolated the magnitude 4.2 and "stretched" it out. One can see from the horizontal scale that the vibrations continued for two or three minutes at our location. The quake would have been a few quick jolts near the epicenter, but the unit is far more sensitive than humans are. The really big quakes can reverberate for hours.
The unit shouldn't really be on the third floor of the building, because it catches all manner of foot traffic, trains and traffic. On the other hand, what a great teaching tool. I've used a signal splitter to put a second monitor in the window with some interpretive notes. I've had any number of people who've stopped by to jump up and down, creating their own little earthquakes (about magnitude -2, I understand).
Thursday, November 20, 2014
Wednesday, November 19, 2014
|What else are you going to call a restaurant situated right on the San Andreas?|
|Mission San Juan Bautista and the scarp of the San Andreas fault|
There is a very slight chance (5% or less) that this quake is a foreshock to a larger magnitude event, as the San Andreas fault has over a century of accumulated stress. There is no way to say until a larger quake takes place. It is good to have moderate quakes like this once in a while to remind all of us of the necessity of being prepared. The larger quakes, when they come, will cause extreme damage to our infrastructure, meaning power outages lasting for days, disruptions of transportation corridors and communications (no internet!). Always have an emergency kit with extra water, food, radio, flashlight, batteries, and first aid supplies in your house and in your car.
|Source: Southern California Earthquake Data Center|
|Vernal swales on the summit area of Table Mountain. These have some similarity to vernal pools on the valley floor but are also different in some important respects. Click on this post for more info.|
|Vernal swale on Table Mountain above Jamestown in the Sierra Nevada foothills|
There is very little of the original California prairie left, no more than five or ten percent. A lot of what is left has already been altered by grazing, but such lands are not getting particularly worse under that form of land use. It seems we hear that this new development or that one will only take only a few more acres, and a few more. Repeat over and over, and the last of the pools will be gone, especially if the politicians go through with their plans to restrict the power of the Environment Protection Agency and other government organizations to do their jobs and enforce the law.
|Vernal pool east of Modesto|
Read more here: http://www.modbee.com/news/local/oakdale/article4005292.html#storylink=cpy
|So many trees, so little water to keep them alive. But profit is profit.|
From March 14, 2014: The Water Pirates: A Can a Day is All We Ask (plus 107 million gallons)
|New orchard on the California prairie|
This could describe the effects of the California Gold Rush of the 1850s, but unfortunately it is not. It is a story that is happening right now in my neck of the woods (prairie?), and the worst of the destruction still lies ahead. And right now, there isn't a whole lot anyone can do to stop it. It's not gold, it's water. And despite the fact that gold is worth somewhere around $1,000 an ounce, the water is far more valuable.
Our local paper, the Modesto Bee, has been running a series of reports recently including this one by reporter J.N. Sbranti that should receive much wider exposure. Almonds have become a valuable and profitable commodity these days, and there is a wild rush on to plant as many acres of almonds as possible. In many cases farmers are simply switching from corn or other yearly crops and putting in orchards. The most destructive aspect, however is the planting of some 30,000 acres of almonds and other nut trees on the former prairie and grazing lands east of Modesto adjacent to the foothills of the Sierra Nevada.
The problem with the trees on the valley floor is that one can't let the fields lie fallow in the driest of years like the one we are now suffering through. The trees must be watered or they die, and they require 4 acre-feet of water per acre each year. If the water gets prohibitively expensive, so what? They'll have to pay the price.
|California's version of "snow". The almonds are beautiful when they are blooming.|
What's worse are those almond orchards in the foothills. They can't be irrigated by normal means, as there is no infrastructure to deliver water there from the local irrigation district. The only source of water is from the ground, and there are few if any rules regarding the use of the groundwater. The large agribusinesses simply buy up the cheap grazing lands, put in the trees, and start pumping vast amounts of groundwater to water them. According to the Sbranti report in the Bee, the 30,000 acres of new orchards are consuming 39 billion gallons of groundwater each year, which is more than is currently pumped for domestic use across the entire county. The groundwater resource is limited, and will likely be depleted in the service of these orchards. When the water runs out, the orchards will die, but the owners will have gotten their cash. All legally of course, and damn the consequences.
It's all well and good to complain about government regulations, but theoretically government exists to watch over the well-being of the citizens. When there is no governance, the pirates take over, and we all lose. There oughta be a law, but I don't hear about anyone working on it. Much too arcane a political issue. At least until the wells run dry...
Tuesday, November 18, 2014
"A City Divided!" "Rift Tears City Apart!" "Slip-Sliding Away!" "Creepiness on the Calaveras"... I Give up: "Calaveras Fault in Hollister"
Like the San Andreas in this region, the fault is creeping instead of storing up seismic stress, moving perhaps a quarter inch per year. Curbs, streets and foundations are all slowly cracking and moving apart.
DeRose Winery, especially on wine-tasting day (and no, none of my students imbibed on Saturday)! The winery, the oldest in California, is several miles south of Hollister on Cienega Road. The San Andreas fault runs right through the winery warehouse and is slowly tearing the building apart. A culvert on the south side of the building shows very well the continuing offset along the fault.
If your travels ever bring you to central California in region around Monterey or Santa Cruz, it's not hard to find your way to Hollister. It's worth your time!
Monday, November 17, 2014
Dinosaurs, Volcanoes, Monsters of the Deep, and Other Stories Told by a Pile of Rocks. And Disneyland.
On those long evenings, we would ride every ride possible, and around midnight we would be exhausted. Everything was starting to close up, but there was one last ride we could do...the train. It passed through the diorama of the Grand Canyon and then it passed onwards into the Primeval World. I'm pretty sure that every misconception I ever had about dinosaurs and ancient life was shaped by the scenes that passed before me in that dark tunnel. If you've never had the opportunity, someone (probably many, really) has it posted on YouTube (thank you, Dan Smith):
One of the associations that was imprinted on my mind was the T-Rex battling a Stegosaurus with an erupting volcano in the background. I look at the diorama today and see Apatosaurs lolling in swamps (they didn't), Tyrannosaurs standing like tripods (they didn't), and other misconceptions, but it was always the lavas in the distance behind the battling dinosaurs that I remember so well. So, what possible connection could there be between childhood memories of Disneyland and yesterday's class field trip to the Coast Ranges? Bear with me!
Our first stop of the day was at San Luis Reservoir, a major storage site for the California Water Project. Water is drawn from the Sacramento River Delta and pumped into the reservoir where it is eventually sent south through an extensive canal system. It is the largest "off-river" reservoir in the country. Shoreline erosion has removed the extensive coating of soil, exposing the underlying rocks, a unit known as the Panoche Formation, a complex of conglomerate, sandstone, silt, and claystone that was deposited in Late Cretaceous time, the final years of the Mesozoic, the dinosaur era.
The rocks seemingly defy explanation. They formed in thousands of feet of water, in the forearc basin that developed on the landward side of a vast subduction zone/trench system that existed on the west coast of North America for millions of years. The subduction zone was eventually replaced in central California by the San Andreas fault, a transform boundary between the Pacific and North American plates. The thing about these rocks is that on an ocean bottom one tends to expect to find mud and silt. Sand, pebbles, and boulders don't make sense. There are no strong currents on the ocean floor like there are in rivers. Or are there?
On river deltas and on the edge of the continental shelf where shallow ocean floor gives way to steeper slopes leading to abyssal depths sediments may be shaken loose, by earthquakes for instance. In this situation sediment gravity flows and turbidity currents form, fast-moving bottom-hugging masses of sediment moving very fast into deeper water. These masses are capable of considerable feats of underwater erosion, carving deep submarine canyons into the continental shelf. There are many examples of these along the present-day coast of California, the Monterey Canyon being one of the most famous.
|Source: U.S. Geologic Survey|
So, dinosaurs and volcanoes? The boulders in the Panoche Formation contain the occasional piece of granite derived from the deep erosion of the Sierra Nevada. The granite cobble is a fragment of what once were the magma chambers for a vast system of volcanoes that would have closely resembled the Andes or the Cascades. Yosemite Valley and the other exposures of granite across the Sierra Nevada were once situated miles beneath volcanoes. In Cretaceous time. Meaning dinosaurs once wandered the flanks of volcanoes right here in California!
That's kind of a stretch, isn't it? Is there actually any evidence of the actual volcanoes? And what about the dinosaurs?
The volcanoes are the easiest to prove. Most of the rocks in the photos above are volcanic in origin. They are the eroded pieces of lava flows that once adorned the summit ridges of the Sierra Nevada much as Lassen Peak and Mt. Shasta do today in the Cascades. It really stokes my imagination to pick up one of these rocks and to realize it started as a mass of molten rock that was erupted onto the flanks of a large stratovolcano off to the east. The lava flow was eventually eroded and removed, the bits and pieces being carried in a river and dumped onto a river delta at the edge of the continent. One day the edge of the continental shelf was shaken by an earthquake, and the chunk of rock disappeared into the depths, carried along by a turbulent mix of water and sediment. It came to rest on the deep ocean floor. Eventually intense compression folded and lifted up the rocks, and finally a last bit of soil washed away and the rocks were once again exposed to erosion and trampling by the feet of geologists.Proving the dinosaurs were here is a bit harder, but it happened. In the 1930s, a young teenager from Gustine was exploring Del Puerto Canyon in the Coast Ranges looking for fossil shells. What he found instead were the remains of a Saurolophus, a duck-billed dinosaur. It was the first dinosaur fossil ever found in California. How much more exciting can that be? The dinosaur was apparently drowned in a river flood, and the carcass floated out to sea where it eventually sank to the seafloor.
|Plotosaurus is one of the genera of Mosasaurs. P. bennisoni was the species found in the California Coast Ranges.|
For a description of some recent research on the conglomerates of the Panoche formation check out: http://www.searchanddiscovery.com/abstracts/html/2013/90162pacific/abstracts/green.htm
Saturday, November 15, 2014
Why did the San Andreas Fault Cross the Road? Why did the Road Cross the San Andreas Fault? 12 Years of Geologic Change
These changes that happen at a rate visible in human lifetimes add up to huge changes when multiplied by thousands or millions of years. The nearby eroded volcano of Pinnacles National Park has been displaced 195 miles (315 kilometers) in the last 20 million years or so by movement along the San Andreas.
Friday, November 14, 2014
We live in the most spectacular of times, and in so many ways humans have accomplished incredible feats, with explorations out to the voids of space and into the micro-world of atoms, quarks, and strings. What happened this week? Humans built a machine, threw it into space and let it drift for ten years through intense radiation fields, turned it on, and orbited a comet. They let loose a lander that, despite glitches (like bouncing a kilometer or more), landed and conducted observations and experiments.
We've landed on other planets. We've put telescopes into space that act like time machines, looking back to the early years of the existence of the Universe. We are about to place machines in orbit around Pluto, and around the largest asteroid (2015 is going to be a good year). The Cassini has been orbiting Saturn for years, taking incredible images, like those of the sun reflecting off the seas of Titan. And Jupiter and Mars before that. We've been back to Mercury.
We are learning more about the Cosmos, the Earth, life, and ourselves than has ever been known. Every field of science is a continuing adventure, each week an odyssey of discovery. New dinosaurs, cures for diseases, new insights to the nature of matter itself.
|Telescope night on the roof of the Science Community Center|
Our community knows what they have. Our telescope nights, our planetarium shows, our science lectures, our tours, they are all well attended, sometimes sold out, sometimes standing room only. I was at a telescope viewing and planetarium show tonight, feeling proud of the community I'm living in.
So why depressed? It's this: in the most exciting times of history, when the greatest discoveries of the human adventure are being made, popular media, the best possibility of educating the people who live on the planet, is a visual sewer. The Discovery Channel, the Learning Channel, the History Channel, and others keep putting up tripe of the worst kind, material that reaches for the lowest common denominator: ghost-hunting, paranormal, sasquatch-hunting, hollow-earth documentaries, and now megalodon-hunting. And they work. An uneducated public, apparently incapable of critical thinking, swallows the bait hook, line and sinker. The Discover Channel ran their fake documentary and convinced nearly three quarters of their audience that a creature that went extinct millions of years ago was still living in the seas today.
We have gigantic challenges ahead of us. The climate, affected by global warming, is changing our world in ways that no humans have ever experienced. We are using up critical resources and not finding new ones. We continue to pollute our air and water, and politicians seem hell-bent these days on making things worse ("burn more coal!"). Our hope lies in knowledge, and in an informed and engaged populace who will put pressure on those in power to make things work.
Ignorance can be defeated. Popular media like the Discovery Channel have it in their power to help, and not make things worse.
Tirade over. I wrote fast and angry, and will probably have to fix parts of it, but that's what is nice about blogging. I make my own rules! I'd love to hear your take on the quality of science programming in the popular media today, and what could be done about it.