Saturday, November 16, 2019

Why did the Road Cross the San Andreas Fault? 17 Years of Geologic Change (a new 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 seventeen 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).

On Dec. 2, 2018, 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...

And here is the new update for November 16, 2019: Long-time volunteer Paul provides scale (he has been assisting MJC with field trips for 25 years!). The crack continues to grow, and I wouldn't be surprised if it was patched by next year.
 The paint on the center strip is split even more.
November 2019
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, November 11, 2019

The Last Planetary Transit I'm Ever Likely to See: Mercury Today

The Sun shown just a bit less brightly today, not that anyone could tell. The planet Mercury passed across the disk of the Sun over the space of a few hours this morning, presumably blocking a bit of sunlight from reaching Earth. It was probably the last time I'll ever see a planetary transit.
Today's transit of Mercury (it is just above the center of the Sun's disk).
One needed some special equipment to see the event, mainly a camera or telescope with enough magnification to see the planet, and filters powerful enough to keep the observer from burning out his/her retinas. Luckily, I was able to locate the camera filter I used to observe the solar eclipse in 2017, and my camera has a 60x zoom. In the picture above, Mercury is just above the center of the Sun's disk. When I looked again about 45 minutes later, the planet had clearly moved to the right across the Solar disk (below).
Today's transit of Mercury (it is in the upper right hand quadrant of the picture).
I've seen three transits in my life, today's, Mercury in 2016, and Venus in 2012 (below). The next transit of Mercury is in 2049, when I'll be 92 years old. I may or may not be paying attention then. The next transit of Venus will take place in 2117. I don't expect to be around for that one at all. I wondered whether there would ever be a simultaneous transit of both Mercury and Venus, and it turns out that one will take place on July 26, 69,163 AD. I think I'll let that one pass...
Transit of Venus in 2012

Mercury is the smallest of our "regular" planets, and is even smaller than it appears in the photographs because it is around thirty million miles closer to us than the sun. It's actually not all that much bigger than our own Moon. The planet has been a bit of a stranger for most of time because it is hard to see in the dusk or twilight, and we've only had two space probes come close. Luckily, one of the probes has been orbiting for the last several years, so we have a treasure store of data on the planet. It was the subject of one of my very first blog posts back in 2008.

Saturday, November 9, 2019

Travels in Cascadia: Acrophobia, Glacierlets, and "Summer" in Whistler, B.C.

Inuksuk near the top of Whistler Mountain. See the note at the end of the post.
Acrophobia, the fear of heights, is an interesting phenomenon. I don't have it, I swear. I have no trouble standing on cliff edges, or climbing up in trees, or flying. Gondolas don't bother me. There are variations and subcategories though. I can stand on a high cliff and look over the edge, but I cannot abide watching someone else do it, especially my students. And I really don't like dangling.

There are lots of creepy heebie-jeebie moments in movies, like "Here's Johnny!", or "the call is coming from inside the house", but none gives me heart palpitations like the opening scene of "Cliffhanger" when Sylvester Stallone is trying to save a young women dangling from a rope over a vast chasm. She falls unfortunately, and I always drop the popcorn while covering my eyes. And then there is that first scene from "Vertical Limit", when not one, but three people fell down the cliff.

In my youth (roughly the ages 12 through 60 years) I was a regular peak bagger and rock clamberer. But I couldn't handle dangling from a rope. I only feel comfortable with solid rock or flooring under my feet. I rappelled down a cliff just once, I've never parachuted or gone hang-gliding, and rides at amusement parks that mimic the experience have never held any appeal for me.

This fact that I hate dangling is the background to today's description of our exploration of British Columbia that we undertook last summer in July. It's because I had to dangle over a cliff in order to see something I really wanted to see: a glacier from above.
Whistler Mountain from the Roundhouse Lodge at the top of the Whistler Gondola.
We were well into our trip by the time we reached the town of Whistler, BC. We had explored the Olympic Peninsula, parts of Vancouver Island, crossed the Strait of Georgia, and wandered for days in Howe Sound, the southernmost fjord on the west coast of North America. We drove there on a modern highway, much of which was stapled onto cliffs of Howe Sound. Before the highway was completed (in the 1960s) and improved and widened in the early 2000s (in preparation for the Winter Olympics of 2010), Whistler was an isolated logging community. Today it is a busy recreational center, winter and summer.

On the day we arrived in town it was a little hard to tell which season it was July and it was cold and rainy. It could hardly be anything different (under the rules of Murphy's Law) since our weather thus far had been rather nice, and I was looking forward to seeing the spectacular alpine scenery around Whistler (my previous two visits had been in poor weather as well). We had scheduled only a few activities in the morning so the students could do some exploring on their own during the long afternoon.
The Peak Express ski lift leading to the summit of Whistler Mountain
As a major winter recreation site, the mountainsides are draped with all manner of gondolas and ski lifts, as well as some incredibly long ziplines. A single ticket provided access to most of the gondolas and the ski lifts that were running in the summer, so I headed up the Whistler Gondola, with the intention of riding and walking over a glacier for the first time (I've been to Athabasca Glacier, but not over it). There was also something up there called the Cloudraker Skybridge and the Raven's Eye that sounded worth checking out.

So this is where we talk about acrophobia. I had no problem with the gondola ride at all. It's in an enclosed space with seats and a floor and all that. But when I got out at the Roundhouse Lodge at 6,069 feet, I found that I was still 1,100 feet below the summit of Whistler Mountain. And I would have to get their via...a ski lift. A spindly rickety dangling ski lift. I know all you skiers out there are used to these things, but I'm not. I don't like them. But it was the only way to get to the top of Whistler Mountain within our time constraints, so I hiked over to the base of the cliff and loaded myself onto the lift.
The Cloudraker Skybridge and Raven's Eye (on the far right). The "snow" is actually the top of a glacier.
There are a few places I've been that feel like no human should really be there. At the very bottom of a huge open-pit mine, for instance. One looks at the rocks exposed for the first time in millions or billions of years, and it just doesn't feel comfortable. Standing two feet from flowing lava. And dangling from a thin cable over a cliff of crumbling rock. It just didn't feel right. But there I was, and soon I reached the top no worse for the wear.
Walking out onto the Cloudraker Skybridge. The Raven's Eye is in the distance, upper left.

Once I was on solid ground again I felt better. I walked over to the Skybridge and crossed it several times. It didn't bother me one bit, and I had a great view down the small glacier beneath my feet. Glacier is perhaps a strong word for what this icefield was. A glacier is defined mainly as a mass of ice large enough to flow under the influence of gravity, and this one qualified, but I suspect the rate of movement is on the order of a few inches or feet per year. The term glacierlet is sometimes applied to these ice fields (most Sierra Nevada glaciers are of about this magnitude in size).
It was immediately clear that this glacier was only a shadow of its former self. On the slope far below I could make out a barren ridge surrounding a turquoise lakelet with a couple of huge boulders. This was a very young terminal moraine, so young that plants had not had a chance to grow. The glacier ended down there only a hundred or so years ago. Although there is snow in the lower reaches, the actual glacier ends today hundreds of feet above the lake.
Terminal moraine and moraine lake at the former end of the glacier at Whistler Mountain.

The true size of the glacier today can be seen in a satellite image taken in the late summer when nearly all of the snow (but not glacial ice) has melted away (below). The loss of glacial ice is a worldwide phenomena indicating that the global climate is warming. When these glaciers disappear, their loss will have serious ramifications for the regional ecosystem. The glaciers serve as a dependable year-round water source for alpine creeks, and when that disappears, so will the animals and plants that are dependent on that water. They don't have anywhere else to retreat to.
Meanwhile, I had one more challenge. As physics tells us, what goes up must come down, and I had been procrastinating, walking around the nature trails around the peak of Whistler Mountain. I was out of time, and was going to have to take the ski lift back down. I'm glad no one was with me, because I was whimpering "oh, sh*t" over and over as the ski lift chair tipped over the edge of the void.
The arete on the east side of the glacier. The ski lift went right over it.
The scenery gave me something else to concentrate on, so I snapped lots and lots of mostly useless pictures, but I did get a decent perspective on the terminal moraine and small moraine lake behind it. The turquoise color is caused by clay-sized particles suspended in the water, derived from the grinding action of the glacier on the rocks at its base. An arete is a sharp jagged ridge that divides glacial valleys. The ski lift carried me right over the top of it.

You'll all be happy to know that I gathered myself together and was not whimpering by the time I reached the bottom of the lift.
In the end, the lousy weather mostly kept me from seeing the spectacular alpine scenery that surrounds Whistler. On the other hand I was able to see a glacier up close, and learned to live with my subtle form of acrophobia.
Google Earth image of the small glacier at Whistler Mountain. The cirque is the bowl-shaped valley where the glacier originates. The skybridge traverses the upper end of the cirque.
The Inuksuk at the beginning of the post was the icon of the 2010 Winter Olympics that were held in Vancouver and Whistler. The stone men have been a part of Inuit and other Arctic cultures for thousands of years. The use of the Inuksuk at the winter games was somewhat controversial, as no Inuits ever lived within hundreds of miles of the site of the games. The local First Nations people were the Squamish and Lil'wat.

Whistler refers to the Hoary Marmots found in the region. I saw one of them at the Roundhouse Lodge when I got back from the mountain.

Sunday, November 3, 2019

A Bit of "Where's Waldo the River Otter?" at the San Luis National Wildlife Refuge

There are things in my life that are more thrilling than spotting River Otters (Lontra Canadensis), but there are not many of them. I spend a lot of time on the Tuolumne River where it flows through my town, and also at the local national wildlife refuges, including the Merced, the San Luis, and the San Joaquin. I'm usually searching for birds, but a bit of my attention is always watching for rarely seen mammals like beavers, foxes, and especially River Otters.
We were on the eastern leg of the San Luis NWR Waterfowl Auto-Tour when I spotted what I thought were four ducks bunched together. But they didn't look right, and after a moment I realized that it was a family of River Otters playing on the banks of the irrigation canal. We played a brief game of hide and seek (I mostly hid behind the car), and they eventually swam away downstream (down-canal?).

Most of the time I forget that I have a fully functional video with my camera, but I thought of video first this time around and got a short shot of the family swimming away together. Then I snapped pictures as I could in the dim shadows where they were hiding. What I noticed later is that in each picture of an individual, there was actually a second otter photo-bombing the shot. Can you find the extra otter in each picture?

River Otters in California took a real beating over the centuries of European occupation in California, with trapping and destruction of their habitat by gold mining, damming, and urbanization causing a drastic drop in their population and range. With efforts at reclaiming the river environments in the Bay Area and Central Valley, they have begun to spread out again. A pair of otters was even seen in Yosemite Valley a year or two ago.

I've seen otters on a number of occasions on the Tuolumne River, but this was my first sighting at the San Luis refuge, which is part of the San Joaquin River drainage. The river had been decimated by reservoir construction decades ago and the river was dry for many tens of miles in the San Joaquin Valley, but recent agreements have resulted in a new river, with the potential of even the return of the salmon. The otters will surely follow!