Thursday, December 6, 2018

Wait a Minute...What Happened to the Rocks I Picked Out?

Something kind of extraordinary happened on campus this week. I was pausing between classes and saw a large truck and a crane downstairs in the staging area for the Great Valley Outdoor Nature Lab. The crane was dumping gigantic rocks onto the ground. "My" rock collection had arrived!! You might remember that early last month I went 'rock collecting' in the Sierra Nevada foothills for the rocks that will be part of the displays and landscaping of the outdoor. All 60 tons or so...
My response about their arrival on campus was predictable...

But if you remember the scene in "Elf" when Buddy thought Santa was in the store only to discover he was a fake, well, I had that moment too. I saw that something was off about the rocks I had selected. Something was different about them. Below was the rock that I selected a month ago, when it was 85 degrees out, and rain had not fallen in months...
And here (below) is the rock they claim I picked out. This after nearly two weeks of rain and cooler temperatures. This rock is clearly on a PALLET of LIES!

Well, okay, maybe it isn't on a pallet like the others, and maybe it is the same rock I picked out. But you can now see one of the main reasons I picked it, and why it will be sitting in a position of honor by the entrance sign to the outdoor nature lab. Not only is it a unique rock that is found in our region (the latite of Table Mountain), it is also a miniature ecosystem of mosses, lichens, grass, and other organisms. To see it, just add water!
In any case, we now have an astounding variety of the rocks that are found in our region. There is marble from the Calaveras Complex, the host rock of the many caverns that are found in the Sierra Nevada foothills.
There is a gigantic chunk of the quartz from the Mother Lode veins, the source of the gold that played such a huge (and devastating) part in the history of California. Sorry, no visible gold (although I'll keep looking).
One of the most striking rocks are the "tombstone rocks" of the Foothills Terrane, large fins of slate and phyllite that were once mud and silt on the ocean floor. The rocks were crushed against the western edge of North America, metamorphosed, and tilted vertically. We'll be putting them in the ground in the same vertical orientation. It will be a dramatic sight at the southern entrance to the lab.

The next step comes at the end of the week. I'll get to help direct the placement of the rocks! I'll try not to be insufferably picky..."Could you rotate that one about four inches? Great! Wait...I liked it better the way it was...". An update will follow.

Tuesday, December 4, 2018

Why did the Road Cross the San Andreas Fault? 16 Years of Geologic Change (an Update)

I've been leading geology field studies trips to lots of places in the American West for 30 years and started to take digital pictures in 2001. I sometimes struggle to find new things to photograph when I visit a place for the 30th time, but in some cases it is not a problem. There are geologic changes that happen on a yearly basis, and with sixteen years of photos, the changes become obvious. This is a continuing update from a post in 2013, and I'll probably continue updating for the foreseeable future.
Highway 25 in the California Coast Ranges connects the town of Hollister with the access road to Pinnacles National Park (formerly Pinnacles National Monument). Along the way the highway crosses the San Andreas fault in a section where the fault creeps an inch or so each year (36°35'54.27"N, 121°11'40.19"W). Most years we've stopped to have a look at the effect the movement has on the pavement. In 2002 and 2004, the damage was obvious.
By 2008 someone had patched the road, and no fault motion was evident.
Little damage was evident in 2009 either. But by 2010 cracks had begun to appear as the fault stressed the pavement.
The fact that the fault creeps in this region is a good thing. It means that stress is not building along the fault surface, but instead is being released gradually. The sections of the fault to the north and south of the creeping section are locked by friction, and are building up the ominous stress that will eventually produce quakes with magnitudes in the range of 7.5 to 8.0. The quakes are coming and we need to be as prepared as possible.
By 2012, the road had been completely repaved, and  yet the shearing was already evident.
It became even more pronounced by 2013 and in 2014. Just by chance, the person working as a scale was the same individual as in 2004.

In 2015 the fractures were moderately larger. They'll need to start thinking of road repairs before long.
In 2016 Laura once again provided scale, as she did in 2014 and 2004.
Here in 2017, long-time trip volunteer Mary provides scale. The cracks in the road are just a bit larger, but they didn't look appreciably different than the previous year except for a twist (pun intended).

And so we come to Sunday's (Dec. 2, 2018) look at the road. The break to my eye seems more continuous. It's now been six years since the road was completely repaved.

Last year the paint was deformed (twisted), but not split (below).
The offset paint strip reminds me of illustrations of elastic rebound theory, the idea that stress builds up on a fault line over time. In that model, the land on either side of the fault is distorted over time until the frictional resistance is overcome and the rock snaps back to its original shape. That won't be happening with the paint. Last year in 2017 I said "if they don't repair the road (as they often do; see above), it will probably show a clear break by next year." Here's what transpired:

First, a close-up on 2017's center stripe...
And here's how it looked on Sunday, Dec. 2, 2018:
As predicted, the break in the paint is complete!

So now we await next year's trip...

These little 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.

Monday, December 3, 2018

How Much Can Happen in a Minute? The Anchorage Earthquake of 11/30/18

The Anchorage Alaska 7.0 magnitude earthquake as measured at Modesto Junior College

Attention must be paid. If you are one of my friends or readers in California or Nevada, you need to watch this. If you live in Oregon or Washington, you need to watch this. If you live in any place where earthquakes are a serious possibility, you need to watch. Why? Because when your time comes and you must undergo the ordeal of a major earthquake, you need to be ready, both for the duration of the quake itself, and in the aftermath. These people handled things pretty well.

In a nutshell, realize that your building will remain standing and you won't have time to get out of it anyway. What you'll need to do is not panic and take shelter from debris that could fall from the ceiling or walls. Be a helper as Mr. Rogers would put it and reassure the others around you so they won't panic either.

In the aftermath, check yourself and others for injuries. Get to a safe place, as there will be aftershocks. Stay off the phones; they should be used for emergencies only during the first hours after the quake. You should already have prepared a first aid kit for your home and your car, and you should have water supplies in both places as well. You should also have a plan in place for reuniting your family. This is often best accomplished by having an out of the region relative being the contact person.
Source: U.S. Geological Survey

The most important thing you can do right now is education yourself about the earthquake risks in your home region. The U.S. Geological Survey and state agencies are always a good place to start. You may live outside of California, but you might be surprised at the possibilities for damaging quakes in other parts of the country.

The damage in Anchorage was extensive and the residents have my prayers and best wishes. But it is very notable that Alaska has had high architecture standards because of the magnitude 9.2 quake in 1964, and it paid off. At the last report I heard there were no deaths and few injuries. California also has high standards; in most cases you can trust the buildings will weather the quake. Just do your part to make sure the people do okay as well.

Monday, November 26, 2018

Fall Finally Arrives, California Style

I would never try to compare our fall season with the hardwood forests of New England and the Appalachians, or even with the aspen groves of Colorado or Utah. But there are a few benefits to experiencing fall here in California.
For one thing, our fall lasts for a couple of months, and our trees are at the height of their color at a time when the trees back east are barren of leaves, and winter-style snows are lashing the landscape. It was 68 degrees out yesterday (though we had a day of light frost last week).
I walked the Tuolumne Parkway Trail this morning after a week on the road, and the changes were pretty obvious. The willows and wild grapes were changing.

There are also some mature cottonwood trees that have been various shades of yellow for weeks now.
But we also have some brilliant colors in the city as well. I had errands in town and took a few shots of the Modesto neighborhoods where Modesto Ash was planted many years ago.
There are other ornamental trees on our west campus that are relatively young, and they turned almost fluorescent over the holiday weekend.
So yes, I would never presume to say our fall show of color can compare to the wild displays back east, but I certainly enjoy having a few weeks to appreciate the changes that are happening here right now.
There is a lot of horror going on right now in so many places. I'll be back to trying to right the wrongs soon, but for a few moments today I took a few breaths of blessedly clean air (the Camp Fire is out, thank heavens) and enjoyed the technicolor show.

Monday, November 19, 2018

The Way It Was: The Deep Grassy Valley of the Ahwahnee

No geology exposition in today's post. Our state is choking in a toxic inversion layer filled with ash and particulate soot that is a sad reminder of the lives lost and lives destroyed by a horrific wildfire in the North State. Just for today, a reminder that beauty surrounds us in the depths of tragedy and suffering.
Half Dome reflected in the waters of the Merced River at Sentinel Bridge
Ahwahnee was the Native American name for Yosemite Valley. It's meaning is muddled in time, but it probably means the "Big Mouth", or the "Deep Grassy Valley". It was an island of clear skies and clean air above the smoke and ash. We only had a few hours to visit, so we headed to Sentinel Bridge for a short stroll, and as the sun set in the west we made for the Gateway View at the west end of the valley.
Sentinel Rock from Sentinel Bridge
Sentinel Rock is an astounding vertical cliff that rises nearly 3,000 feet above the valley floor. It receives somewhat less attention than some other rocks and cliffs in Yosemite Valley because it rises behind people who are staring in awe at Yosemite Falls on the north side of the valley.
Yosemite Point and the dry Yosemite Falls
Speaking of Yosemite Falls, there wasn't much to see of them. There was the barest trickle of water that did no more than wet part of the cliff. That should change this week as the first winter storm of year arrives (weeks late). We need it desperately, and many storms thereafter. When the falls aren't there, one's eyes are free to wander over the incredible cliffs that surround the dry watercourse. Yosemite Point and the Lost Arrow stood out boldly in the sun (in the picture above).
We barely had time to reach the Gateway View before the sun settled below the horizon. Only the vertical face of El Capitan was still catching the rays of light, and it soon faded.
The Moon peeked out from the cliffs to our right.
As the valley floor settled into darkness, the sky still glowed. It was a peaceful scene, filled with a serenity that is so sadly lacking right now. We enjoyed the scene until the darkness descended and we headed home.

To help those whose lives have been destroyed in the fire, you can find some ideas here:

Friday, November 16, 2018

A Journey of Ten Million Years...the Salmon of the Sierra Nevada

Chinook Salmon attempting to enter the fish ladder at Camanche Dam on the Mokelumne River
They've been coming here for at least ten million years. Every year, without fail. The lands changed, but still they came. If one waterway was blocked, they eventually found another. Sometimes they were isolated, and could never return to the sea, but they survived anyway. They are the salmon and trout of the Sierra Nevada.
Stanislaus River at Knight's Ferry

Anadromous fish are those that live much of their lives in the oceans, but which return to freshwater streams to reproduce. One might wonder why they would have such a complicated breeding scheme. In all likelihood, it had to do with the survival of the young fish. Rivers and streams tend to offer more hiding places than open ocean, and the young have a chance to grow large enough to survive. The most familiar of these fish are the various species of salmon and Steelhead Trout. I had several opportunities to view the November migration of the Chinook Salmon this week on three different rivers: the Mokelumne, the Tuolumne, and the Stanislaus.
In historical times, the fish ranged far into the interior of the Sierra Nevada and Cascades Range, being stopped only by cascades and waterfalls too high for them to jump. They numbered in the millions. As European and American colonizers replaced the Native Americans across the state, the fish began a steep decline.

One of the first and worst events was the Gold Rush of 1848. Miners tore up miles and miles of river gravels and disrupted the flow of the rivers with their placer mines (sluices, long-toms, and cradles). Hydraulic mines (water cannons) ripped away billions of cubic yards of gravels from the hillsides and choked riverbeds with egg-smothering silt and clay. Vast amounts of water were diverted from river headwaters to feed the hydraulic mines through a system of flumes and pipelines.

Somehow the fish survived this onslaught, but then something more insidious happened. The dam-makers arrived in the late 1800s and early 1900s to build reservoirs to divert water for irrigation purposes. The dams themselves were barriers to the upstream movement of the fish, but even worse was that water diversions left the rivers to small and warm for their survival. The mega-dams were constructed in the 1960s and 1970s, diverting even more water. One river, the San Joaquin, ceased to flow most years over a stretch of about sixty miles. By the time the last dam was built, more than 95% of the historical breeding grounds for the fish had been made inaccessible to their migration (see the map below).
The blue portions of the rivers have salmon. The historical range is shown in black. Source:
Millions of years ago, this landscape was much different. The Sierra Crest was lower than it is today, but the summit region was covered by volcanic complexes not unlike the Lassen Peak complex and other parts of the Cascades. Periodic eruptions sent steaming lahars (volcanic mudflows) down the river canyons and onto the floor of the Great Valley (which may have actually been a shallow sea in this area). The rocks from this time period, 5 to 12 million years ago, are called the Mehrten Formation and they can be found throughout the Mother Lode foothills.

The Mehrten Formation has yielded up a treasure trove of fossil species. At Turlock Lake fossils were found of Giant Tortoises and Oncorhynchus rastrosus, the Spike-toothed Salmon. These remarkable salmon were as long as eight feet. They apparently used their "tusks" to fight for territory. Otherwise their lives were similar to the salmon of today. The riverbanks were populated by horses, camels, bison, antelope, giant ground sloths, mastodons, and carnivores, including the ancestors of the bears and wolves. The woodlands were dominated by sycamore and oak. For an excellent overview of the fossil record, check out the technical article by Sankey, Biewer and others, or read their excellent book The Giant Spike-Toothed Salmon and Other Extinct Wildlife of Central California.
Oncorhynchus rastrosus, the Giant Spike-toothed Salmon. Artist: Jake Biewer

Erosional processes steal nutrients from the land and carry them to the sea. It has been remarked that salmon and other anadromous fish return the gift. After they fight their way up the streams and rivers, and after they lay and fertilize their eggs, the fish die. Their bodies provide food for a host of carnivores and scavengers. Long before I found any fish in the Mokelumne River the other day I sensed the lurking presence of several dozen Turkey Vultures. I wasn't actually thinking about fish at that moment, but wondered why so many vultures were hanging around the river.

Moments later the reason was clear, as many were already feasting on the dead fish. The alert eyes that followed the movement of the fish are of an ancient lineage as well. Turkey Vultures are the most common of the avian scavengers, but their ancestors and Condor relatives patrolled these rivers millions of years ago.
These fish have survived for at least ten million years, and it has taken only a century and a half to threaten their very existence. Even now intense controversy follows the negotiations over how much water to devote to agriculture and how much to preserve the future of the salmon and the entire ecosystem that they inhabit. It's not a fish versus people proposition as some have portrayed it. It is a larger question of whether we want to preserve healthy river habitats for clean water, a diverse ecosystem, and for our own recreation and inspiration. Agricultural interests in the drainage of the San Joaquin showed in the 1940s that they were more than willing to destroy a river to apportion every drop of water. Things began to change in the 2000s as agreements were reached to restore flows to the lower river and bring back viable populations of Chinook Salmon. I hope we can be as wise in the other water conflicts around the San Joaquin Valley.

These videos are from the Mokelumne River below Camanche Reservoir, the end of the road for the Chinook Salmon. I had never visited the area before, so I was exploring the trails at the day use area below the fish hatchery. There were lots of fish in the river, and large numbers of them were struggling to break through the gates of the fish ladder, which was closed. I followed the fish ladder into the hatchery grounds, wondering if it actually provided access to the reservoir, but it didn't. It led to holding ponds that were already full of salmon. When the fish are ready, the eggs are harvested and fertilized, providing the stock for the hatchery. The young fish are later released into the river at the hatchery and other locations downstream.

These hatcheries are one way of dealing with the devastating loss of habitat for the salmon, but it seems it would be better if we could provide access to their ancestral breeding grounds upstream. I don't claim any expertise in these matters, but there have to be better answers than what we see happening today. They've been here for at least ten million years, and deserve a chance to be around for a few more.