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Information board shows the evolution of the valley over the last 8 Ma (In Spanish, but legible if you click +
Hollister, California
In the San Francisco Bay area there are three major faults, from west to east the San Andreas, the Hayward, and the Calaveras; all are part of the San Andreas fault system. All of these are "right-lateral strike-slip faults," which means that the motion is predominantly horizontal, with the land on the west side of the fault moving north.
South of the Bay Area the Hayward and Calaveras merge into the San Andreas. Hollister is located just north of where this happens, right on top of the southern end of the Calaveras fault.
What makes Hollister particularly interesting is that from San Juan Bautista to just north of Parkfield the faults in the San Andreas system are not "stuck": instead of moving only during major earthquakes, they continuously "creep." As a result of this creep, Hollister is being slowly ripped in two, for the most part along a remarkably narrow zone running right through the middle of town.
The rate of creep is inconsistent, and has been measured at between 6 and 15mm per year at various times throughout the 20th century. Underground pipes, road paving, curbing, and foundations all show signs of being gradually shifted apart. Notice how the distortion always bends structures to the right- no matter from which side of the fault the photo was taken. Also notice that the motion is horizontal: the ground is remaining level as it moves. Together, these two observations define right-lateral strike-slip motion.
Fault (two rock formations have moved relative to each other) at the head of the geo between Gote o' Tram and Girston Geo. The fracture zone is the dark line in the right-corner. Photographed on 11 April 2009.
On my second visit to Lake Cowal back in early December, I was told about a place that was of great interest to geologists visiting the nearby gold mine. This trip I headed out to have a look.
Following is the information I was given to explain what I was going to see.
"The outcrop is part of the Booberoi Fault and features sheared Late Silurian-Early Devonian Edols Conglomerate (Sherwin, 1996) showing stretched quartzite and vein-quartz pebbles in a quartz white mica-chlorite matrix, which was probably a muddy sandstone. Mesoscopic kinematic indicators show at least two movement episodes: a horizontal sinstral movement and a near vertical reverse (west side up) movement. The movement direction can be discerned from the asymmetry of the matrix surrounding the pebbles and the mineral elongation within the matrix."
Video - youtu.be/gFIb1JXFTb8
This was earthquake country, a stretch of rural California countryside in what I think is the San Joaquin valley, headed toward Yosemite. Videos I've seen of fault country show portions of the San Andreas passing through places like this, though I know we'd already passed over the fault closer to San Francisco. Incidentally, this is located in Calaveras County, site of the famed Twain story.
I love California countryside, the farmland and fences and trees. There is a very weird way in which it almost remainds me of my pre-Chicago home.
Side note: Map viewers take note, my placement of this photo is somewhat specualtive. The road's right, but this might have been shot anywhere within 20 miles of my randomly chosen location.
As far as I can see all these shots are uneven in focus/out of focus, this is due to me Dropping the camera last summer, probably the last ones I will shoot with the camera
On my second visit to Lake Cowal back in early December, I was told about a place that was of great interest to geologists visiting the nearby gold mine. This trip I headed out to have a look.
Following is the information I was given to explain what I was going to see.
"The outcrop is part of the Booberoi Fault and features sheared Late Silurian-Early Devonian Edols Conglomerate (Sherwin, 1996) showing stretched quartzite and vein-quartz pebbles in a quartz white mica-chlorite matrix, which was probably a muddy sandstone. Mesoscopic kinematic indicators show at least two movement episodes: a horizontal sinstral movement and a near vertical reverse (west side up) movement. The movement direction can be discerned from the asymmetry of the matrix surrounding the pebbles and the mineral elongation within the matrix."
Video - youtu.be/gFIb1JXFTb8
"The Fault" by Viviane Silvers, a sculpture at Vanderbilt featuring a baby reaching out to a woman who's turning away sadly. Very strange.
On my second visit to Lake Cowal back in early December, I was told about a place that was of great interest to geologists visiting the nearby gold mine. This trip I headed out to have a look.
Following is the information I was given to explain what I was going to see.
"The outcrop is part of the Booberoi Fault and features sheared Late Silurian-Early Devonian Edols Conglomerate (Sherwin, 1996) showing stretched quartzite and vein-quartz pebbles in a quartz white mica-chlorite matrix, which was probably a muddy sandstone. Mesoscopic kinematic indicators show at least two movement episodes: a horizontal sinstral movement and a near vertical reverse (west side up) movement. The movement direction can be discerned from the asymmetry of the matrix surrounding the pebbles and the mineral elongation within the matrix."
Video - youtu.be/gFIb1JXFTb8
Hollister, California
In the San Francisco Bay area there are three major faults, from west to east the San Andreas, the Hayward, and the Calaveras; all are part of the San Andreas fault system. All of these are "right-lateral strike-slip faults," which means that the motion is predominantly horizontal, with the land on the west side of the fault moving north.
South of the Bay Area the Hayward and Calaveras merge into the San Andreas. Hollister is located just north of where this happens, right on top of the southern end of the Calaveras fault.
What makes Hollister particularly interesting is that from San Juan Bautista to just north of Parkfield the faults in the San Andreas system are not "stuck": instead of moving only during major earthquakes, they continuously "creep." As a result of this creep, Hollister is being slowly ripped in two, for the most part along a remarkably narrow zone running right through the middle of town.
The rate of creep is inconsistent, and has been measured at between 6 and 15mm per year at various times throughout the 20th century. Underground pipes, road paving, curbing, and foundations all show signs of being gradually shifted apart. Notice how the distortion always bends structures to the right- no matter from which side of the fault the photo was taken. Also notice that the motion is horizontal: the ground is remaining level as it moves. Together, these two observations define right-lateral strike-slip motion.
Hollister, California
In the San Francisco Bay area there are three major faults, from west to east the San Andreas, the Hayward, and the Calaveras; all are part of the San Andreas fault system. All of these are "right-lateral strike-slip faults," which means that the motion is predominantly horizontal, with the land on the west side of the fault moving north.
South of the Bay Area the Hayward and Calaveras merge into the San Andreas. Hollister is located just north of where this happens, right on top of the southern end of the Calaveras fault.
What makes Hollister particularly interesting is that from San Juan Bautista to just north of Parkfield the faults in the San Andreas system are not "stuck": instead of moving only during major earthquakes, they continuously "creep." As a result of this creep, Hollister is being slowly ripped in two, for the most part along a remarkably narrow zone running right through the middle of town.
The rate of creep is inconsistent, and has been measured at between 6 and 15mm per year at various times throughout the 20th century. Underground pipes, road paving, curbing, and foundations all show signs of being gradually shifted apart. Notice how the distortion always bends structures to the right- no matter from which side of the fault the photo was taken. Also notice that the motion is horizontal: the ground is remaining level as it moves. Together, these two observations define right-lateral strike-slip motion.
Once supplied with a link to purchase Teen Witch, I couldn't be stopped... however, I haven't clicked Max Out Your Credit Card yet...
And I did hold back... another $100 in DVDs (which is actually just 2 Collector's Sets), have been placed on my wishlist.
Hollister, California
In the San Francisco Bay area there are three major faults, from west to east the San Andreas, the Hayward, and the Calaveras; all are part of the San Andreas fault system. All of these are "right-lateral strike-slip faults," which means that the motion is predominantly horizontal, with the land on the west side of the fault moving north.
South of the Bay Area the Hayward and Calaveras merge into the San Andreas. Hollister is located just north of where this happens, right on top of the southern end of the Calaveras fault.
What makes Hollister particularly interesting is that from San Juan Bautista to just north of Parkfield the faults in the San Andreas system are not "stuck": instead of moving only during major earthquakes, they continuously "creep." As a result of this creep, Hollister is being slowly ripped in two, for the most part along a remarkably narrow zone running right through the middle of town.
The rate of creep is inconsistent, and has been measured at between 6 and 15mm per year at various times throughout the 20th century. Underground pipes, road paving, curbing, and foundations all show signs of being gradually shifted apart. Notice how the distortion always bends structures to the right- no matter from which side of the fault the photo was taken. Also notice that the motion is horizontal: the ground is remaining level as it moves. Together, these two observations define right-lateral strike-slip motion.