The latest installment of Accretionary Wedge is a call to write about the “most memorable/significant geologic event that you’ve directly experienced”. This will be my first contribution to Accretionary Wedge, so if I’m doing it wrong, someone please let me know!
When I first heard the topic, I thought “well, I grew up in Southern California, so I’ve experienced lots of geologic events.” I’ve experienced more earthquakes than I can remember.
The 1994 Northridge quake knocked me out of bed.
I felt the 1987 Whittier Narrows quake while walking to school.
Then there was the one (unnamed, as far as I know) that occurred while I was in the shower, and my 14 year old self panicked at the thought of having to run outside naked.
I was in San Francisco a few weeks after the 1989 Loma Prieta quake, so while I didn’t feel it personally, I saw the aftermath up close.
I was at Mt St Helens a few months after the 1980 eruption. Again, not a direct experience of the event itself, but that experience is certainly something I’ll never forget.
(The real question here is why I didn’t become seriously interested in geology until a couple years ago!)
I have no pictures of my own to go with any of those events, so, while memorable, none deserve a dedicated blog post.
But a few months ago I got to experience something that will stay with me for a long time, and I’ve got lots of pictures to go with it, and I’ve been neglecting this blog for far too long, so here goes.
In mid-September I went to Zion National Park. I drove down from Provo on a Wednesday. I was still a couple hours away when a thunderstorm started up, but it was mostly gone by the time I got to the park.
By the time I got set up in the campground, the day was absolutely gorgeous.
The next day, the weather remained beautiful, but the Virgin River was clearly carrying a heavy sediment load from the previous afternoon’s storm.
That afternoon, I went on a ranger-led hike, and heard about Zion’s ephemeral waterfalls. I was disappointed that I’d missed them.
By Friday morning, most of the sediment was gone.
I took that picture across the road from Zion Lodge, where I was going to attend a ranger talk. One hour later, this was the view across from the Lodge:
It’s hard to see exactly what’s going on there because of the rain between me and the rock. But you can see, there in the middle, one of those waterfalls I’d heard about. This wasn’t a little shower, this was a deluge, complete with hail.
A couple dozen of us were huddled under the bus shelter waiting it out. (During the tourist season, private vehicles are not allowed in the upper canyon. You have to take a shuttle bus to get to most places in the main canyon.)
Then we heard the news that there was a mudslide over the road down canyon from the Lodge, so we were stranded indefinitely. Most people went inside, but the thought of standing around with a bunch of soaked, grumpy people didn’t appeal to me. So I stayed outside and watched the waterfalls grow…
…and change colors…
…and create beautiful veils of streaming water.
It turns out that the mudslide wasn’t as bad as it sounded, and was cleared (at least enough to allow the shuttles to pass) within an hour. This is what it looked like when I finally got on a shuttle bus.
That’s supposed to be the road.
Compare the sediment load here (from the Visitors’ Center) to the one above near the Lodge. This picture was less than two hours later.
Things had settled down by that evening, and our ranger-led shuttle tour went on as planned. The ranger told us that the discharge had gone from 60 cfs to 800 cfs during the storm.
I don’t know if it’s possible to say how much of Zion left the park via the Virgin River that day, but I was glad that I was able to witness a small (teeny, tiny) part of the millions of years old process.
So. Winter. I didn’t know it started in October. I had planned to be on the road until a couple weeks before Christmas, but when the weather started turning bad while I was hanging in Canada, I panicked a little bit. So I decided to start my wintering in Southern California a little early.
I thought I would be smart and take a route that approximated Route 66, taking me well south of the snow. Ha! I stopped for the night in the middle of Missouri, only to get a dusting of snow on my way out in the morning. And then I stopped for the night in Flagstaff, Arizona. And the snow found me. In Arizona! That’s my car under 4 inches of it up there.
So now I’m in Southern California for a while. The rest of the continent can have winter. I had my share in Arizona.
But then I start to think about the natural disasters or near disasters that occurred in the places I’ve been either shortly before or after I was there. There was the earthquake and then hurricane in the Northeast, a snowstorm in Zion & Bryce, a bigger snowstorm in Denver, and a huge snowstorm in New England, the earthquake in the East Bay, earthquake in Oklahoma.
If I were a superstitious person, I’d be thinking twice about staying in one place for any period of time.
So even though I won’t be traveling for the next few months, I’m so far behind in writing about what I’ve done already, so that should keep me busy for a while.
I just realized that it has been a month since I posted a blog entry. I am so very negligent. I could give you a million reasons, like the fact that I’ve driven through 21 states (and into another country!) since the events of my last entry. Or that I’ve been sick and drunk on Nyquil (except when driving) for the last week. I could tell you that this particular post has been sitting on my computer in partially-finished draft form for several weeks. But I know that none of those sorry excuses can assuage your anguish over going a whole month without me waxing prosaic on topics I know next to nothing about. So I’ll give you part one of this post now, and I’ll finish it up soon and post the rest.
This time the title is accurate, because ewwwwww. But we’ll come back to that.
Just like there was ancient Lake Lahontan in Nevada, there was ancient Lake Bonneville in Utah. And driving through western Utah, you see evidence of it everywhere. At its maximum, it was a huge lake.
(Image borrowed from USGS website)
My route cut a diagonal from the Nevada border, to just north of Sevier Lake, past Utah Lake, and then north to Salt Lake City. Sevier Lake is now dry, as you can see from this photo of its salt flat. It is filled by the Sevier River, but most of the water is diverted for agriculture around the town of Delta. What little water does enter the lakebed quickly evaporates.
All three of the current lakes (Sevier Lake, Utah Lake, and Great Salt Lake) are remnants of Lake Bonneville, and everywhere along that route, you see evidence of its former glory.
Based on where I was when I took this shot (halfway between Delta and Utah Lake), I believe we’re seeing wave cut platforms from the Provo and Bonneville levels of Lake Bonneville. You see, the various water levels are so well demarcated in so many places, they’ve given names to all the water levels. You can see a great animated map of the levels here.
Oh, and did you notice the sunflowers along the road? They’re everywhere. And I do mean everywhere. I think every road in Utah, other than city streets, has sunflowers along the road. It’s awesome.
So once I got to Salt Lake City, I really wanted to see the Great Salt Lake, and maybe wade in it. You know, just because. And I found a totally unexpected gem of a park in the middle of the lake: Antelope Island State Park.
Antelope Island is one of 11 islands in the Great Salt Lake. To get to the park, you drive across a causeway from the town of Syracuse.
Incidentally, while driving through Syracuse on my way to the park, somebody’s horses were running around on the street. I hope they got them under control and nobody got hurt.
So, remember the whole Basin & Range thing I talked about before? Well, Antelope Island is one of the ranges. It just so happens that its particular basin has a bunch of water in it, so it’s an island.
An island, by the way, that is covered with sunflowers. Sunflowers make me happy in a way no other flower does. It totally made my week to see so many of them in Utah.
So, if I had to pick one word to describe the lake itself, it would be “gross”. I’ll show you why. You see these brown masses on the beach at Badger Bay?
This is what they look like up close.
Those are dead brine fly larvae. You see, there isn’t much that can live in the super salty water of the Great Salt Lake. But brine flies do. And the wind blows them into these great stinky piles on the beaches.
There are still plenty of them in the water, though.
And on the beach. So, yeah, I took my sandal off, stuck my toes in, took a picture, and high tailed it out of there.
Oh look, more sunflowers. Happy thoughts, happy thoughts.
So, you’re thinking, being right in the middle of the Great Salt Lake, there must be more Lake Bonneville wave cut platforms visible there. And you’re right.
You can see every named level of Lake Bonneville on the island.
You can see sunflowers, too.
Coming up in part two: big animals, old rocks, and yellow flowers.
After leaving Lake Tahoe, I headed east down the Sierras on US-50, intending to drive across Nevada in one afternoon. I ended up spending three days there.
The stretch of US-50 through Nevada is called “The Loneliest Road in America” because there are only 5 towns along the route and almost nothing in between. Actually, it wasn’t very lonely at all, because there were plenty of other cars traveling in both directions. However, there were a few times where I could no see no cars either ahead of me or behind me. And you can usually see quite far on this road.
The state tourism board (or whatever it’s called) has even come up with this little “passport” book that you can get stamped at all five towns and send in to get an “I Survived the Loneliest Road” certificate. I got my book stamped, so we’ll see when I get the certificate.
I saw more different kinds of “___ Crossing” signs during my transit across Nevada than I have ever seen: Bear (in Lake Tahoe), Deer, Horse, Cow, Antelope(?), Fire Truck, and Tractor.
One thing about this road is that if you’re at all unclear about what the term “Basin and Range” means, US-50 will straighten you right out.
That’s all you see driving across Nevada: Basins (valleys) and Ranges (mountains). You can see that very easily on a topo map.
All of these small, north-south oriented mountain ranges separated by valleys. Well, those mountain ranges weren’t always so small. The Basin and Range province is being created by extension of the crust, because the movement of the Pacific plate along the San Andreas Fault is creating tension on the crust.
What happens when you start pulling crust apart? It breaks into faults. These faults run north-south roughly parallel with the orientation of the San Andreas. These are normal faults, where the two blocks separate, thus making the crust longer and thinner. But underneath these roughly vertical normal faults are horizontal detachment faults. So the blocks don’t just separate in a linear fashion, they slide down and rotate.
The result of this is that one edge of the rotated block is left sticking up, forming a mountain range. The other block has dropped down along that axis, and forms the valley. Incidentally, the technical terms for the mountain and valley are “horst” and “graben”. I just love those words. Especially graben. Graben. Say it a couple times and I know it’ll grow on you too.
So the mountains and valleys formed and then the mountains immediately started undergoing erosion. And they’ve been doing this for millions and millions of years. In some places, the sediment filling the valleys is tens of thousands of feet thick.
Whenever you get this crustal extension, volcanic activity is not far behind. Although it’s not right out in your face, the volcanism can be seen if you know where to look. And one of those places is the very first interesting spot along the road.
Just past Fallon (town #2 for the passport book) is Grimes Point. This is a field strewn with basalt boulders covered with petroglyphs.
These petroglyphs were created by scraping away a layer of desert varnish covering these basalt boulders.
Desert varnish is created by oxidation of manganese by bacteria.
The symbols are thought to have had mystical power in helping with game hunting.
You might wonder “What game? Aren’t you in the middle of the desert?”. This area is now a desert, but it was once a lakeside location. Around 12,000 years ago, a large portion of Nevada was covered by Lake Lahontan, which was up to 700 feet deep.
In the distant hills, you can barely make out the wave cut platforms, showing the various water levels of the lakes. Now when the Native Americans who made these petroglyphs lived in the area, the water level was much below its maximum, but the water was still there. And where there’s water, there’s game.
These petroglyphs are as much as 7000 years old. Very nearby Grimes Point is Naval Air Station Fallon. This is the home of the TOPGUN Naval Fighter Weapons School. Which means that while you’re walking the trail around these ancient inscriptions, you’re hearing and seeing (mostly hearing) these flying overhead:
It took a couple tries before I actually got a shot of these. I kept looking in the direction the sound was coming from, but then I figured out that they are nowhere the sound by the time you hear it. I have no idea what they are.
The next interesting point is just a little further down the road. And Sand Mountain really is quite striking. Even though it’s a desert, there’s really not much sand along this road. In fact, most of the bare ground is covered with desert pavement. Desert pavement forms when wind blows away all the small particles, leaving only densely packed stones at the surface.
But here is a mountain of sand! (You can see some desert pavement to the left of the road in this picture.) Remember that old Lake Lahontan? Well it was here, too. And it left a lot of sand in this area, which got blown around. As it turns out, Sand Mountain sits at point where the winds hit a mountain range, lose their energy, and deposit all their sand.
Right next to Sand Mountain, you can see very clearly some of the wave cut platforms from Lake Lahontan.
The next stop on the tour was Fairview Peak. This is a fault trace exposed by a magnitude 7.1 earthquake on December 16, 1954.
You can see how much displacement there was here, but there’s even more displacement further up the road.
Fairview Peak sits at the eastern edge of one of the “Ranges”, and this picture is looking south. So the ground to the left (east) moved down and that to the right (west) moved up. This stretched the crust a little bit more, so the creation of the Basin and Range province is still continuing!
One last stop before ending my first day in Nevada: Stokes Castle
This was built by Anson Stokes in 1897 to be a summer home for his family. He was the owner of a railroad that ran between the nearby town of Austin and Battle Mountain. After building the “castle”, the family lived there for a month and then abandoned it.
So after my first day of driving through Nevada, I’d barely made it halfway across the state, but I arrived in Austin, town #3 for the passport. The population of Austin is about 300, but they have 4 motels and 2 gas stations, not to mention a few restaurants and stores. Obviously I’m not the only person who feels like they need to stop for the night in Austin.
After spending the night in Austin, and eating breakfast in a former hotel that was moved, piece by piece, from Virginia City, 165 miles away, in 1863, I continued my sojourn east.
The next interesting stop was Hickison Petroglyph Recreation Area. It contains, guess what…petroglyphs!
But before we talk about the petroglyphs, let’s just get this out of the way: There’s a trail to/around the petroglyphs. There are two parking areas, one is right next to the petroglyphs, one is a half mile away, with a trail connecting it.
Not only did I park in the “wrong” parking area, which was totally not my fault because the signs pointing to the two parking areas are labeled “Trailhead” and “Campground” so of course I took the “Trailhead” turn…but once there, I got on the wrong trail. I’ll bear some responsibility for that. It was just carelessness and sloppy map reading. And I’ll also take responsibility for the fact that it took me almost an hour to realize I wasn’t on the alleged half mile trail.
But I got some cool pictures! So these petroglyphs, rather than being carved onto basalt boulders like at Grimes Point, are carved into ash-flow tuff. These rocks are the solidified remnants of a pyroclastic flow. So this is a very different kind of volcanism than that which produced the canvas for the Grimes Point petroglyphs. If you don’t know what a pyroclastic flow is, watch this video:
Commonly found with this kind of tuff are breccias. And this is where my misadventure on the wrong trail becomes a good thing!
I’m not sure what made that cavity, but it’s a window through which you can see all the many bits and pieces that were flung out of the volcano along with all the pyroclastic materials.
Here’s another. Really, these were all over the place. But let’s get back to the petroglyphs.
Isn’t the way this stuff erodes just so cool?
This is a view of Lone Mountain, which is just west of town #4, Eureka. I know this isn’t the best photo, taken through my car window with my cell phone. But I think you can see that there are tilted layers, right?
The oldest layer, at the far left, is Pogonip Limestone. This layer was deposited from the late Cambrian through the middle Ordovician periods, or roughly 550 to 450 million years ago. At this time, most of the North American continent was covered by water, which would be expected because limestone is almost always deposited in marine environments.
The next layer up, a fairly thin but relatively bright white layer, is Eureka Quartzite. This layer of metamorphosed sand was deposited in the middle Ordovician period, around 450 million years ago. It appears that the sand was blown south from Canada.
The next two layers, which are a little difficult to distinguish in my photo, are the Hanson Creek Formation, laid down in the late Ordovician, about 444 million years ago, and the Roberts Mountains Formation, from the early Silurian, around 430 million years ago. A very thin layer of dark chert separates the two strata. These are both limestone layers, indicating a return to a marine environment.
The next, light layer, is the Lone Mountain Formation, a late Silurian (around 416 million years ago) dolomite layer. Next, forming the peak of the mountain, is a dark layer, the early to middle Devonian Nevada Formation dolomite. So we’re still underwater.
Not much further along the road is Devils Gate. Here we get a close up view of the Nevada Formation, which formed the peak of Lone Mountain just about 10 miles back.
I don’t have much to say about town #4, Eureka, or #5, Ely. I pretty much stopped just long enough to get my passport book stamped and moved on.
I took this picture because the color contrast of this mountain was striking. I can’t find a name for this mountain, but it turns out to be the site of Rose Cave. (If you click and zoom in, you can see the cave entrance behind the utility pole in the foreground.) This cave is a migratory stop over for Mexican free-tailed bats. But guano is useful for production of industrial chemicals, so they started mining it here in the 1920s. To expedite the mining, they dug a tunnel below the natural cave entrance in 1926. Unsurprisingly, this messed up the bats, so in 1998 the tunnel was closed off. There is now concern that new wind power turbines in the area might kill the bats.
Ok last stop in Nevada was….Great Basin National Park. I was only there not even 24 hours, but I think I had the absolutely most awesome campsite ever. EVER!
Allow me to give you a tour:
From my parking space, I had to cross a footbridge over creek #1.
Then a short walk to the table/tent area.
From which you discover that creek #1 is actually composed of creeks 1A and 1B.
And on the other side, creek #2, which is actually creeks 2A and 2B.
So to give you an idea of what I got to listen to all night:
I no longer need any of those white noise CDs, because I made my own.
Notice how green and lush everything is. Surprising, no? I mean it’s right in the middle of the desert.
The highest mountain in Great Basin is Wheeler Peak.
It’s the one on the right with the nearly vertical face.
From this view, you can very nicely see the cirque and the rock glacier. As you can see, the weather was starting to get ugly, and the road up to this point was scary enough when perfectly dry. I didn’t want to be descending it in a downpour. Fortunately, the other big attraction in Great Basin is totally weather-independent.
This is Lehman Caves. And man is it hard to take pictures in here without a tripod. And they don’t allow you to bring tripods on the guided tour. So, these are the best I could do.
So I spent a few days in Lake Tahoe. Well, I wasn’t in Lake Tahoe for a few days, more like a couple minutes. And I was in all the way to my ankles. But I was in the area for a few days. Was it ever gorgeous.
I dare you to click on that and not fall instantly in love.
Or how about that one?
Or that one?
It seems like everywhere you look there’s a breathtaking view. And knowing a little about the processes that made those views makes it all the more spectacular. But is the geology of the Sierra Nevada ever complicated. So many things going on in the same place (but not at the same time).
First you have to know that the eastern side of the Sierra Nevada was once the west coast of North America. But then the Atlantic Ocean started opening up, and shoved North America to the west, where it smashed into the Pacific plate, which started subducting and scraping off bits and smashing them up against the North American plate. Those rocks are now the eastern side of the Sierra Nevada and North America has grown a bit and is at about the line of the Sierras.
And then it happened again, adding more smooshed and folded and deformed rocks and growing North America even further west. And these rocks form the center and western side of the Sierras.
And then…again! And those rocks form the Sacramento Valley all the way out to the current coast.
And while all this is going on, there are volcanoes. Because you can’t have subduction without volcanoes. That’s just how it works. So all this magma of varying compositions is working its way up from way down deep in the earth. Some of the more mafic (basaltic) magma would blurp up into the more felsic (granitic) magma. And then they’d solidify as plutonic rocks and eventually get exposed by erosion. And you’d get inclusions like this:
When you know what these are, you suddenly notice they’re everywhere. Like 3 of every 4 hunks of granite you see have these inclusions. Technically these are gabbro, which is chemically identical to basalt, but has larger crystals because it cooled slowly. (The same is true of granite and rhyolite: granite cooled slowly and has large crystals; rhyolite cooled quickly and has small crystals).
Oh and because of all this magmatic heat and water from the subducted plate moving around you get quartz veins.
Sometimes you see rocks with both! And of course, where you have quartz veins, you have gold. So there was a lot of gold pulled out of the Sierras back in the 19th century, and it left a huge mark on the appearance of the area. A lot of the damage has since been covered over by tree growth, but at one point, mining operations dumped so much sediment into the Sacramento River, that the river flooded and destroyed tons of agricultural land in the Sacramento Valley.
Oh did I mention the glaciers? As if all of this subduction and volcanism weren’t enough, there were massive glaciers in the Sierras during the ice ages.
It’s not hard to see that there were glaciers when you see something like this huge erratic on the shore of Donner Lake. No force short of ginormous could have moved this here. And glaciers qualify as ginormous.
I’d like to think that these linear erosions are evidence of glacial activity, too. But I’m not certain. Glaciers are famous for leaving boulders with striations or scratches, because it’s not like they’re pure ice. They’ve got all kinds of gravel and rocks riding along with them. Maybe these striations created another surface for erosion, which deepened them and allowed more room for freeze-thaw cycles to expand them further. I found some pretty dramatic examples of this same process, if that’s what it is.
Oh and there’s one more element to the geology of Lake Tahoe. It is the western end of the Basin and Range province. I’ll talk more about that in my next post, but for now just know that it involves lots and lots of faults that create valleys (that’s the Basin part) and mountains (that’s the Range). Lake Tahoe actually lies in one of those basins, and its eastern side is one of those ranges (the Carson Range).
So the whole story goes something like this:
Repeated rounds of subduction caused mountain building and volcanism, while glaciation was carving and eroding the growing mountains. Meanwhile, faulting from the Basin and Range province split those mountains in two, creating a valley which filled with water after a volcanic eruption closed its main outlet, leaving the Truckee River as its sole, pitiful outlet. Ice dams from melting glaciers sometimes blocked this outlet, causing the water level to rise greatly until the ice dams broke, unleashing huge torrents of water which further sculpted the area. Glaciers also created features like Emerald Bay:
Ok enough talk. Let’s get back to the pretty pictures.
In the above picture of Mt. Tallac, you can see some of the small glaciers that remain. Glaciers flow from the heads of valleys called cirques, which are usually steep on the uphill side and open on the downhill side. And they pick up lots of debris as they scourpad their way down the mountain, leaving it in great piles called moraines. You can see both cirques and moraines in this picture.
That last one is actually Spooner Lake, the one I mentioned in a previous post. As promised, here are some better pictures of the fire fighting helicopter that was scooping water out of the lake for a nearby fire.
Donner Pass is very close to Lake Tahoe, so I took a quick trip out there. I’m sure you all know the story of the Donner Party: group of pioneers try to get to California by wagon train, take a bad shortcut that adds weeks to their trip, get stuck by early snows in the Sierras, half of them die, the other half eat the dead ones, the end. Or something like that.
The base of this memorial shows high the snow was that year. Near that memorial is this boulder.
It’s interesting for a few reasons:
There’s a plaque on it! It lists the names of every member of the Donner Party, and whether they died or survived.
It actually formed the wall and fireplace of the cabin that the Murphy family lived in.
It’s huge! It’s clearly a glacial erratic.
It seems really complicated. Now, there’s a lot of dark lichen growing on it, so it’s tough to decipher for my inexperienced eyes, but it seems like it’s a granite intrusion into something else. And the granite intrusion has its own dark inclusions.
But not everything in the area is granite. Like I said there’s lots of other stuff going on in these mountains. Like serpentinite.
At least I think that’s what this is. It’s weathered into a rather unattractive color.
This might be an example of exfoliation, where the rock is weathering by peeling like an onion. Or maybe it’s just been plucked at by a glacier. Either way, the ever present inclusions are there.
I believe that’s an andesite boulder along the shore of Donner Lake. So more evidence of volcanism.
I think this is an Atlantis fritillary, based on my cursory glance at a field guide. But I’m no expert!
I have no idea what this little guy is!
These were the biggest dandelions I’ve ever seen. As big as my fist. And I don’t have dainty hands.
This golden-mantled ground squirrel was posing for me.
As was this deer near Spooner Lake.
And its parents(?) nearby.
I think that’s a good sampling of what I saw at Lake Tahoe. See you next time!
I took another field trip during my stay in the Bay Area: to Napa Valley. Unfortunately, I picked Labor Day weekend to do this, and everyone else in the Western Hemisphere was doing the same thing. Between the crowds and the fact that I was driving, I abstained from imbibing the local spirits.
But, like me, my day was not totally wasted, because I found a few geologically interesting places. The thing that most defines Napa Valley, besides the wine, is the volcanism. Back when there was subduction happening on the coast of California, there was a string of volcanoes along the continental margin, usually 50 to 200 miles from the subduction trench. This is always the case when you have subduction because that oceanic plate dives into the mantle, melts, and goes the only way it can go: up! This is still going on in the Cascades, as well as in Alaska, and Japan, and Chile…hey that’s pretty much the whole Ring of Fire thing, isn’t it?
One of the old volcanoes is Mt St Helena, because we don’t have enough volcanoes in this country with names like that.
It’s one of these, I think the one in the back. About 3.5 million years ago, one of these volcanoes erupted. And this was a pretty massive eruption. This was a felsic magma, which means it had a high silica content, which means it was very viscous and held onto gasses, which means that when it erupted, it was violently explosive. When this kind of lava cools quickly, you get rhyolite. In this picture, you can see little vesicles, indicating that there was still gas in this lava when it cooled.
This stuff is everywhere in the area around Calistoga. In fact, it’s this volcanic history that’s responsible for Calistoga’s famous hot springs. But we’ll get back to that in a little bit.
All this rhyolite buried a redwood forest. The wood tissue was eventually replaced by silicate minerals and the result is a petrified forest! It’s the only petrified forest in California and the only one to contain primarily petrified redwood trees.
Here’s a petrified redwood. It was about 2000 years old when the volcano blast knocked it down.
Here you can see how well the bark is preserved.
You can see the minerals that replaced the wood tissue. Some of the petrified trees are really quite lovely.
Here’s one that doesn’t really look like much from afar.
But up close, isn’t it beautiful?
This one is so large, they didn’t even excavate the entire thing. They just built a little mine shaft of sorts to extend back over 100 feet.
You can see how thick this layer of volcanic rock is over the tree.
Here are some more petrified trees:
That last one is called the “Robert Louis Stevenson” tree, and it does kind of look like a face with the shadows… Actually he stayed in the area for a time and wrote the book “Silverado Squatters” about his time there.
This is a beautiful piece of petrified wood in the fireplace of the museum/gift shop at the Petrified Forest.
The other cool thing I found in Calistoga was the “Old Faithful” geyser. Now I know what you’re thinking, Old Faithful is at Yellowstone, but apparently this name is something that any geyser can have as long it erupts fairly regularly. And this one was going off at 20 minute intervals while I was there, although it depends on how much groundwater there is which depends on how the precipitation has been. Here is the geyser pre-eruption.
What happens in a geyser is that the groundwater is sitting in cavities below ground, absorbing heat. What’s the source of the heat? A magma body. Now all of the volcanoes in the area are quite extinct, and haven’t erupted in millions of years, but there is still magma down there somewhere. In fact, there is at least one (maybe more) geothermal power plant in the area.
So the water is getting hot, but it doesn’t boil because it’s underground where the pressure is higher, so it gets superheated, meaning it’s above the boiling point. But hot water does expand, so the expanding water eventually fills all the little chambers until there’s no space left but to escape through the opening to the surface. This sudden release is like opening a shaken soda can. The weight of the water that escaped reduced the pressure on the water below it, causing the remaining water to instantly boil and erupt.
The eruption starts small with just some steam and a few burbles of water. But then it really gets going.
And if you have nothing better to do with 6 minutes of your life than watch water shoot out of the ground, here’s a video.
And if you do have nothing better to do, welcome to my sad little world.
But! That’s not all you get for your $10 at Old Faithful of California. I don’t know about you, but the first thing I think of when I think “geyser” is “fainting goats”, followed immediately by “Satanic freak-sheep”.
You’re not imagining things. That sheep does have four horns. It’s a Jacob sheep, and they can have up to six!
I swear this one was dreaming. It would occasionally lift its (her?) head just a bit and baaaa very softly but never open its eyes. It would also kick its legs rhythmically for a few seconds.
Last stop of the day was Clearlake, which is allegedly the largest lake in California.
I can’t really say how clear it is, but it smelled like a high density cattle feed lot. I don’t know why, but after standing next to it for a couple minutes, I started getting nauseous.
My guidebook said there would be obsidian visible in the roadcuts on the western side of the lake, and there were. Unfortunately there was no safe place to stop to take pictures. Other roadcuts south of the lake were serpentinite, but again, no safe place to stop. You’ll just have to take my word for it!
I’m going to leave you with one last photo, a hillside vineyard with an extinct volcano in the background, perfectly representative of the Napa Valley.
While I was in the Bay Area, I did some touristy things, like riding the cable cars.
I think they used the same model for the safety tips sign as for the “watch out for illegal immigrants” signs along I-5 near San Diego.
Riding the cable cars is fun, but as I mentioned before, San Francisco is pretty hilly.
And there is that moment when you’re approaching the top of a hill and your heart skips a beat as you wonder where the road went.
And then you’re going down the hill and you think to yourself, “Wow. If the brakes failed right now, we’d all be dead. Because, you know, you’re basically riding a park bench down the hill.”
That’s actually not the worst hill. On the worst one, I was too scared to move let alone take pictures.
I also went to Alcatraz, because what says fun like a defunct high-security prison?
Don’t drop the soap!
Getting thrown in solitary gets a nice view of nothing once that door is closed, but with the added bonus of knowing that San Francisco is visible through the windows right outside your own personal hell.
The old warden’s house. I guess excellent ventilation is one of the perks of being the head honcho.
There’s a time capsule! I’m not sure I’ll be around when it’s opened, but here’s hoping!
How’d you like to eat three meals a day knowing there are canisters of tear gas hanging right above your head?
Alcatraz is no escape from the hills. They tell you, several times, that the walk from the boat dock to the main cell block is the equivalent of 13 stories. It’s also no escape from the birds. In fact, if you’re afraid of birds, you’d probably want to avoid the place like the plague the birds probably carry.
It’s hard to see in that picture, but there are hundreds, if not thousands of birds down there. They’re everywhere. And the whole island smells like bird crap. You can’t escape it.
While I was on the boat waiting to leave, something set the birds off, and they all took to wing at the same time. It was freaky, like a Hitchcock flick.
And then they started flying over the boat, which left me covering my head in desperation to avoid being a target. And as you leave, the birds mock you from the warning sign, because these prisoners need no help escaping.
While in San Francisco, I ate a ton of sourdough bread. That stuff is addictive. Who knew some meager little bacteria could produce something so wondrous? But I didn’t take any pictures. And for Monique:
Alas, I did not spend all my time in the Bay Area wandering around San Francisco. I also went to the Winchester Mystery House in San Jose. They don’t let you take pictures inside, and I forgot my camera anyway, so here’s a cell phone shot of the outside.
The place is kooky but fun. I love the winding staircases with the teeny-tiny risers, even though they made me dizzy. Hey, can I make a geology link here? I can! the house was damaged quite badly in the 1906 San Francisco earthquake (there used to be a seven story tower but it came out of the quake leaning and had to be demolished) and Mrs Winchester was trapped in one of her rooms for several hours because all the walls were leaning so badly the doors couldn’t be opened. She thought the spirits were telling her that she was spending too much time working on the front rooms, so she immediately boarded them up and never repaired the damage.
I went looking for some geology, and I found some! First, I went to Hayward to find the Hayward Fault. This fault runs parallel to the San Andreas and was the source of an 1868 earthquake which was called, at the time, The Great San Francisco Earthquake. Of course, that moniker was usurped less than 40 years later.
If you look at a map of the Bay Area, you’ll see a lot of valleys running roughly southeast to northwest. These are all caused by accessory faults to the San Andreas, and run parallel to it.
The path of the Hayward fault is easy to see because it separates the flat lands of the bay from the Berkeley Hills to the east. And it runs right through the cities of Hayward and Fremont.
This is a curb at the corner of Rose and Prospect Streets in Hayward. The fault is running right to left right through this curb. I’m standing on the west side of the fault, and the block I’m on is moving north relative to the east side of the fault. I don’t know when this curb was last aligned, but you can see someone marked a line through it in 2006 (it’s a famous curb!).
It hasn’t moved much in the last 5.5 years, but that’s not necessarily a good sign.
In this shot, I’m looking west down Sunset Blvd from Prospect Street and across the fault. The fact that I’m looking down a hill is due to the fault, and you can see some creep in the sidewalk.
This is the old Hayward city hall, which was built, you guessed it, right across the fault. Oops! It was starting to get too expensive to repair the damage caused by continual creep along the fault, so it was abandoned and a new city hall was built a few blocks away. Even though this building is currently empty, it still looks pretty nice (although there a few broken windows) and I saw no external evidence of fault damage.
It seems that this isn’t an isolated problem! Building city halls on top of faults seems to be the thing to do in the East Bay. Because the city of Fremont did the same thing. Then they discovered that the fault ran right between the support columns. Oops!
Well, as part of that complex they expanded the sag pond and made a nice little park around it.
I had mentioned sag ponds briefly before, but I didn’t really explain how they form. And that’s probably because I didn’t really make the geometric connection, but now I get it, so here goes. I talked before about how the “big bend” in the San Andreas causes a local area of compression. That’s because it’s a left hand bend in a right lateral strike-slip fault. If the bend is a right hand one, you get an area of extension. Since compression gives you mountains, extension gives you valleys. And since water tends to collect at low points, you get sag ponds.
Here’s some really bad art to illustrate. (Man, drawing that with a touch pad was really hard, and I’m pretty artistically challenged anyway.) So all three are right lateral strike-slip faults; see how if you were to stand on one side and look across, the other side is moving to your right in all three cases? The left drawing would be a perfectly straight fault. You get only (or mostly) lateral motion. The middle drawing shows a left hand jog which causes compression and mountains. The right drawing shows a right hand jog which causes extension and sagging.
Incidentally, the Fremont park was filled with Canada geese the day I was there. It was also filled with Canada goose poop. Have you ever seen Canada goose poop? I hope they don’t defecate in flight because if one of those hits your car from a significant height, you’re gonna need some body work.
