A nice slideshow about the Barstow Formation and the fossils it contains, from the San Bernardino County Museum.
Thursday, December 31, 2009
A nice slideshow about the Barstow Formation and the fossils it contains, from the San Bernardino County Museum.
Wednesday, December 30, 2009
|(published by Scope Enterprises, Inc)|
Geologists divide California into eleven geomorphic provinces, areas that share unique geologic histories, rock types and topography that are distinct from the surrounding areas. I generally refer to the province when I am describing a particular feature or place. I am categorizing the posts that exist thus far in the same way:
Say Hello to California's New State Dinosaur, Augustynolophus morrisi: The first dinosaur discovered in California was found in our county, Stanislaus.
The Prairie Lands: California has its own version of savannahs, both present and past.
Sharktooth Hill: That's about it...thousands and thousands of shark teeth and a great many other species.
The Day of the Fiddlenecks (A Trip Through the Mother Lode): A brief foray for wildflowers on Highway 132 in California's Mother Lode
There's an Endemic in those Red Hills! Life and evolution on one of California's unique environments, the serpentine soils. Exploring the Red Hills Area of Critical Environmental Concern
The California State Mineral Exhibit-This is art, darnit! One of the best ways to see the incredible mineral wealth of California is to explore the state mineral exhibit in Mariposa at the south end of the Mother Lode. Because of the morons in the state legislature, it is about to shutter its doors
It's a Real Grind...Chaw'se State Historical Park: A look at more grinding mortars than you'll ever see anywhere else, the Miwok culture, and some interesting metamorphic rocks
The Other California Goes Underground: Hella Hot Helictites at Black Chasm Cave: Never heard of helictites? That's because they are the first cave features to be destroyed. But we have a world class collection of them in the Sierra foothills
What do you do with a Used Forest?: The Sierra Nevada between Yosemite and Kings Canyon National Parks is terra incognita for most Sierra travelers. The region has been logged, mined, and grazed...and is still spectacular. We take an excursion on the Sierra Vista Scenic Byway
Why Worry About Yellowstone? We've got our own "supervolcanoes" in California. Some are active. Some have been extinct for tens of millions of years. At the Minarets we can explore one from the inside out
I've seen these mountains before! The Big Ripoff: Viewed on a geologic map, the Klamath Mountains look like a continuation of the Sierra Nevada, but lie sixty miles farther west.
I Need This Like I Need a Hole in the Head: Scenic Bodega Head at Bodega Bay was the nearly the site of one of the most mind-bogglingly stupid energy developments ever conceived by the minds of engineers
Baymouth Bars - It's Five O'Clock Somewhere? Along the incredibly rugged north coast amid the violent surf there are long, perfectly straight sand bars that seem to defy explanation. They're explained here Humboldt Lagoons State Park
A Mystery Photo For a Saturday: A look at San Francisco from a unique angle, Monte del Diablo
The Thicket of the Devil (the mystery photo revealed): An introduction to a place with an incredible view, Mt. Diablo. How it got its name and why every landowner in Central California should care
Limekiln State Park Part 1, Part 2, and Part 3: Limekiln is a beautiful gem of a state park on the Big Sur Coastline. Unfortunately we have morons in the state legislature and this park is closing. See what is being taken from us
The Calico Mountains: An exploration of a unique mountain range, well beyond the confines of the tourist trap ghost town.
A Monday Mystery Photo: A quick introduction to the Cajon Pass country where the San Andreas fault splits the San Gabriel Mountains from the San Bernardino Mountains
Cajon Pass and No Strange Sci-Fi Creatures: Cajon Pass, the major freeway access route into the Los Angeles basin, is filled with strange looking sedimentary rocks tilted this way and that. But it's not where Captain Kirk fought the Gorn...
The Mountains of My Youth: The eastern San Gabriel Mountains aren't all that familiar to people from outside the state, but they are spectacular and they were the mountains where I grew up. We explore an extraordinary gorge, San Antonio Canyon
Hemming and Hawing on the Hogback: The San Gabriel Mountains are the steepest mountains in the world. Often the only flat spots are on dangerous stream floodplains and on top of landslides. Several examples from San Antonio Canyon include the Hogback and Cow Canyon Saddle
A Canyon as Deep as the Grand, and a Road For No Reason: The Glendora Ridge Road offers some of the greatest panoramas of any road in southern California, and there doesn't seem to be a reason for it being there. I suspect I know what the reason is
The Forbidden Valley: An introduction to the San Dimas Experimental Forest
A Minor Challenge: A quiz to introduce the unusual geology of the Santa Clarita Valley
Dreams of Avarice and the First Gold Rush: You thought the gold rush started in the Sierra Mother Lode? There was a rush six years earlier, but the Mexican miners kept their secrets better (and there wasn't very much gold, either)
The Oldest Rocks (Well, maybe...): The San Gabriel Mountains have very old rocks, maybe the oldest in the state. But it depends on how you define "oldest". A short introduction to radiometric (isotopic) age dating
The Other California: Another Friday Fun Foto: A brief introduction to San Jacinto Peak, the highest mountain in the Peninsular Ranges, and one of the most prominent mountains in the state, with a 10,000 foot slope in one area.
A Mystery Photo for the Day: A view of a rock that looks like it belongs somewhere in the Sierra Nevada, but that is not where it is...
When is a Peninsular Range Not a Peninsula? Baja California is a peninsula, but the rocks continue into Alta California. This post explores the village of Idylwild next to the highest part of the province at San Jacinto Peak
I clearly have lots of ground to cover, and will update this page as necessary.
Tuesday, December 29, 2009
The meadow in the foreground lies along the entrance road to Sunset Crater National Monument, which preserves one of the youngest volcanic features in Arizona. A look east from the same meadow reveals Sunset Crater itself.
Sunday, December 27, 2009
Friday, December 25, 2009
A couple of clues: It is the southwesternmost peak in the United States that shows evidence of Pleistocene glaciation, maybe even the southernmost, period, and also has the southernmost grove of Aspen trees in the United States. As far as the "transformative" part, in the picture above, not one, but two strands of the San Andreas fault lie tucked between the ridges visible in this photograph.
Merry Christmas and happy holidays to all! Thanks to Susan Hayes for the photo.
UPDATE: As Chasmanian Devil and Forrest noted, it is San Gorgonio Peak, the highest mountain in Southern California at an elevation of 11,499 feet. The mountain shrunk three feet over the course of my life, as I grew up in SoCal with the highest point being officially 11,502 feet. It got too heavy, or else the surveying methods improved! San Gorgonio is a fascinating place to hike, especially if you like wilderness: many people follow the trails to the summit, but some wonderful lonely trails explore the flanks of the peak, especially at the headwaters of the Whitewater River. It was glaciated in the Pleistocene ice ages, and recent research has established the precise glacial chronology. It even has a few natural lakes, a rarity in southern California mountains. It's a place I am anxious to get back to! I highly recommend a book by Stephens Press called Call of the Mountains, a beautiful photo-essay about southern California's mountains.
Wednesday, December 23, 2009
Dust storms are a normal phenomenon of deserts, but they are made worse by poor agricultural practices and droughts. According to news reports, the worst dust of this particular storm was the result of plowing in nearby agricultural fields. I find myself wondering if the agribusinesses take high winds into account when they plow potentially dusty dry fields near major transportation corridors. A sign on a highway warning of dust is too easily ignored, and does not absolve those responsible when things go terribly wrong. This sort of tragedy is too common in the Phoenix region, as well as back home in the Central Valley.
Monday, December 21, 2009
It has been my experience that when I look upon a scene of such grandeur, my mind is not fully capable of taking in the true scale of the canyon. The vastness of the scene has been shrunk to a single image in the back of my eye, and my ego makes me much larger in relation to the canyon in front of me. One way to gain a truer sense of scale is to hike the canyon. Nothing drives home the depth of the gorge more than trying to walk back out. It looks a LOT bigger when you stand at the bottom and look up!
On the other hand, one can stand on the rim with a camera, and see what happens to people scaled to the immensity of the canyon. I stood this morning at Mather Point and snapped a shot of people enjoying the view (above).
I was actually some distance away, using a 30x zoom, so I back out to 15x or so, and a strip of the Kiabab Limestone becomes visible. The rock is a mixture of limestone and sandstone that formed in a shallow sea in Permian time, around 250 million years ago.
Sunday, December 20, 2009
Pascal was quite curious about how the creation-scientists would present their ideas on the field trip. Except for some strange questions and occasional references to processes not noted in most geology texts, the trip would not have seemed out of the ordinary to a normal geologist. Pascal discusses the issue of creation-scientists presenting data at science conferences and noted that:
Yes, the YEC crowd will put this as a shining feather in their caps [ironic, since they claim all of our work is wrong yet they view interaction with us as "proof" that their ideas have merit].
The "feather in the cap" has been published by the Institute of Creation Research, and it has some interesting perspectives. I am mostly struck by the way the ICR crowd feels it must hide its motives in their abstracts and field trips. Sure, being labeled a young-earth creationist at a GSA meeting would lead to perception problems, but labels have a reason sometimes.
I often start my classes with the statement that "recent research" indicates that cigarettes don't cause cancer after all. The students catch on pretty fast and ask "who did the research, and who paid for it?" They understand that if the research was presented by the tobacco lobby, that's one thing, but if it was published in a peer-reviewed journal by oncologists supported by the American Cancer Society, that is something else altogether.
So take their statement about two of the abstracts (here and here) presented this year:
Two of these papers were on the petrology of the Coconino Sandstone of the Grand Canyon... (the) Authors ... presented evidence that ocean water, not wind, deposited the distinctive crossbedding of the Coconino Sandstone. The evidence of ocean water currents was argued technically from the dolomite beds, dolomite grains, ooids, mica grains, microfossils, and bimodal texture.
The Coconino Sandstone in the Grand Canyon region is a real problem for young-earth creationist, as are most of the other sedimentary layers on the Colorado Plateau. By their "model" (giant world-wide flood 4,500 years ago), all 12,000 feet of the sedimentary layers of the region HAD to form in ocean environments and under extraordinary conditions at that. All of them. If one of them clearly formed on land, then their "model" is disproven. So the Coconino, generally recognized as a desert sand-dune deposit, had to form underwater. So ask yourself: would these people EVER find evidence of a land-based origin for this layer, or any other layer for that matter? Their researchers must agree with ICR doctrinal statements and tenets just to do research for ICR.
I also take issue with another of their claims. They seem to "take ownership", in a sense, of an organization called the Affiliation of Christian Geologists:
Christian geologists also expressed themselves through an organization within GSA called Affiliation of Christian Geologists. Around 40 GSA members attended the evening meeting ... approximately one third of whom were young-earth creationists. This shows that there are many within the GSA that take seriously the creation and Flood narrative text of the Bible. Their numbers and prominence within GSA appear to have been growing over the years (italics mine).
If you peruse the ACG website, it is apparent that they are reputable geologists who have serious issues with the young-earth creationists. I also have a slight problem of calling the 13 or 14 young-earth creationists "many" when compared to the thousands of geologists in attendance at the meeting.
I don't think creationists should be excluded from venues like GSA. On the contrary, I wish they would present more of their "research". But I would hope that their work will receive the same scrutiny that any poorly designed research would get. If they are trying to prove a worldwide flood 4,500 years ago, then present the evidence to the people who know the science, and be ready to get challenged. Don't hide your motives.
Today's photo is a slab of the Coconino Sandstone showing trackways of an animal walking across the surface of the sand dune. Several dozen different kinds of tracks are commonly found in the unit.
Thursday, December 17, 2009
On the other hand, the FOX Channel's Glenn Beck, fear-monger par excellence, has been shilling for a gold-selling company, while at the same time using his show to advise people to buy gold in these terrifying times. He tells us to "pray over it" ("Dear God and Jesus, should I use my money to give food to the poor, or buy gold???"; I wonder what voice speaks in his head, and what it says to him?). I'm sure there is no conflict of interest here...
I started thinking about gold because one of my very first efforts at web page design (1997, I think) still sits in a largely original state on my school website, a discussion about the history of the gold mining in the Mother Lode. It talks about the value of gold at the time, and the then current state of mining. A recent visitor to the site commented the price of gold had quadrupled since I wrote the piece, and suggested that interest in mining was up again (if you check out the site, be aware that some of my numbers are speculative).
First off, does anyone know of any ongoing interest in reopening any Mother Lode mines? I'd like to know about it. I must say, that if I were already operating a mine, I couldn't be happier. Great prices! But opening, or reopening a mine? Do mining companies trust that the price of gold is going to remain stable or continue to rise? Enough to make the incredible investments in equipment and regulatory paperwork? I've gotta say that the run-up in the price is very reminiscent of the dot.com craziness of the 1990's, the stock market craziness of the 2,000's, and the real estate insanity of the last 10 years. Wow...how'd they all do? What I remember the most was the maniacal exhortations to invest, invest, invest, even as prices started to fall.
If you are thinking of falling for one of these gold investment schemes, take a look at this article by Nouriel Roubini. For the record, he was one of those gloom and doom economists who predicted the ongoing recession-depression (does anyone believe it's over?) before it was fashionable. Can you spell "g-o-l-d b-u-b-b-l-e"? It may a good time to sell gold, but I wouldn't trust a banjo-strumming confidence man. See a reputable jeweler first. As for Glenn Beck and the other investment shills? Well, consider the source...
Late Add: Seems (surprise, surprise!) that some of those commercial gold buyers have gotten in trouble. Check out this report.
Monday, December 14, 2009
November included a tour of Pinnacles National Monument (above), and a Geology Club tour of Natural Bridges near Columbia in the Sierra Nevada Mother Lode.
I spent a fair amount of time close to home, but when you live in Central California, that means a lot of nice places to visit! In January, it was a wintertime journey to Yosemite Valley...
In February, it was our field studies trip to a rather snowy Death Valley National Park. From Dante's View, one looks down a vertical mile to the lowest point in the western hemisphere, near Badwater (-286 feet).
By March, the Sierra Nevada foothills were blooming; these are poppy fields in the Merced River Canyon, seen during our field studies trip in the southern Mother Lode.
In April, it was a return trip to Yosemite, to check out one of the biggest rockfalls in years, at Ahwiyah Rock near Half Dome. Luckily no one was hurt in this one
Sunday, December 13, 2009
A major fault slices across the front of the mountains, the right lateral Calico fault, which provided a major avenue for hot mineralized waters to rise close to the surface. The hot spring activity produced veins of barite, calcite and agate that hosted most of the silver ores. Recent research has indicated that the region is part of a metamorphic core complex that experienced a great deal of extension in Miocene time.
Friday, December 11, 2009
On the former subject, I recommend a short note by four Yale professors describing just where we stand in our understanding of climate change. It provides a good geological perspective to charges that earth's climate has always been changing: it has, but not at the pace we are experiencing today.
From "The Big Picture":
"However, Earth’s history has something to say about climate sensitivity and the role of carbon dioxide, as well.
The reconstruction of Earth’s history reveals a story of slow and rapid climate change and clear evidence for immense variations in temperature. While most discussions in the popular press focus on the past 100 to a few 100,000 years and the precise relationship between carbon dioxide and temperature, it is informative to examine the full range of climate variations over millions of years.
Earth was, in fact, ice-free for most of its history. For example, Earth was much warmer and had no significant polar ice between 65 to about 34 million years ago. Fifty-five million years ago, rapid and massive releases of carbon acidified the oceans and warmed Earth’s surface about 5 degrees Celsius above what was already a warm planet. At peak warming, about 50 million years ago, crocodiles roamed the Arctic amongst subtropical flora and fauna, even though the Sun’s intensity was lower than today. Much higher carbon dioxide during this time is revealed by various paleoclimate reconstructions, and subsequent global cooling is shown to have followed carbon dioxide decline.
Earth’s history tells us that the leading driver of climate change is the concentration of atmospheric carbon dioxide. Not the only driver, but the leading one. It also reveals that climate sensitivity to carbon dioxide is possibly much higher than discussed in policy-making circles. About five million years ago, carbon dioxide was as high or only slightly higher than 2009 values, and Earth reached temperatures 4 degrees Celsius warmer than now, with sea levels tens of meters higher. The present-day location of Yale University was underwater.
Many lines of evidence and study tell us about the effects of carbon dioxide release. In the past, large increases in carbon dioxide corresponded to major warming events. It is unwise to think that today’s increase in carbon dioxide will, for some reason, produce a different outcome."
As to the idea of "manufactured doubt", recall the kinds of things that went on with the connection of smoking with cancer in the 1960's, and concerns about the decline of the ozone layer in our upper atmosphere in the 1970's and 1980's. It's happening again with the political battle (not the scientific debate) over the cause of global warming. For a good review of how to politically manufacture doubt about scientific research, check out this article at the Weather Underground:
"The history of the Manufactured Doubt industry provides clear lessons in evaluating the validity of their attacks on the published peer-reviewed climate change science. One should trust that the think tanks and allied "skeptic" bloggers....will give information designed to protect the profits of the fossil fuel industry. Yes, there are respected scientists with impressive credentials that these think tanks use to voice their views, but these scientists have given up their objectivity and are now working as lobbyists. I don't like to call them skeptics, because all good scientists should be skeptics. Rather, the think tanks scientists are contrarians, bent on discrediting an accepted body of published scientific research for the benefit of the richest and most powerful corporations in history. Virtually none of the "sound science" they are pushing would ever get published in a serious peer-reviewed scientific journal, and indeed the contrarians are not scientific researchers. They are lobbyists. Many of them seem to believe their tactics are justified, since they are fighting a righteous war against eco-freaks determined to trash the economy."
Of course, don't take my word for it. Do some research yourself, and not just from politically motivated sources. Global warming is clearly already affecting our planet, from massive ice loss from Antarctica, Greenland, and the mountain ranges around the planet, earlier and earlier springs, movement of species to higher latitudes and altitudes, larger and more intense wildfires in places like Australia and the western United States, and crippling droughts.
Tuesday, December 8, 2009
Now, it sounds like I'm demeaning the place, but actually I like it a lot. The Kenny Rogers album, long out of print, is one of my most cherished possessions. My family spent a lot of time there, and I even did my senior thesis in the area. It is fun, but it is not "the Other California" of my current blog series. It's on too many postcards and tourist brochures. It turns out the "Other California" can be defined in a few different ways. The magic, to me, of Calico is beneath the surface of the town, and in the surrounding hills, the parts a lot of tourists never hear about.
The ghost town is a genuine historic mining camp. Silver was discovered around 1881, and despite the horrific lack of water and blazing summertime temperatures, the town grew to a population of 1,200 before a drop in the price of silver killed the mines in the 1890's. There are claims that more than $20 million of silver was produced. The discovery of borates nearby caused a brief resurgence in 1907, but the town was abandoned within a few years.
In 1951, the whole town was purchased by Walter Knott (there really is a close connection with the theme park). He took some of the buildings to Orange County to construct the core of his amusement park, but he also rebuilt some of the ruins, and made a tourist attraction in the desert as well. He donated the park to the county in 1966.
Like Bodie, the town was threatened for a time by plans for renewed mining, and the large hill just west of town is criss-crossed with roads for the drilling rigs. The company was probably considering a large open-pit mine at the site. The scheme was eventually abandoned, probably because of low silver prices.
So, what really is special about Calico and the Calico Mountains? That will be in the next post!
Sunday, December 6, 2009
In the decades following the fabled Gold Rush, hungry miners started to explore these regions, and a lucky few found the elusive metal. W. S. Bodey was one of these; his exploration party found gold in 1859 in the hills between Aurora and Mono Lake, a plateau region averaging 8,000 feet above sea level. He may have found the gold, but he wasn't lucky. He froze to death the following year while making a supply run near Mono Lake.
The mines took some time to take off. The discovery of a rich lode in 1876 led to the development of the Standard Mine, and thousands of people came to the town of Bodie (renamed for pronunciation purposes). The population peaked at 10,000 in 1880. The town developed a fearsome reputation for lawlessness, and one legend declared that a young girl, finding that Bodie would be her new home, said "Goodbye God, I'm going to Bodie". The town had its pride, too: an editor of the town newspaper insisted the punctuation was wrong; she had really said "Good, by God, I'm going to Bodie".
The mines were active for years, producing $34 million in gold (at a mixture of prices, $20/ounce in the 1800's and early 1900's, and $36/ounce in the 1930's). The gold is worth a great deal more at today's prices, perhaps $1 or 2 billion. As time went on, gold production waned, and the town began to die away. The Standard Mine (visible in the window reflection in the picture below) shut down in 1913, although sporadic efforts at mining continued through 1942. A disastrous fire in 1932 destroyed most of the buildings in the town (only 167 of the original 2,000 buildings remain).
It was mildly surprising to me that Bodie would be the pick for the California State Gold Rush Ghost Town, given how many historic towns line the Mother Lode in the Sierra Nevada foothills (actually, until I started this series I didn't even know California had an official ghost town). On the other hand, the competition and politics would have been deafening. As it was, controversy did ensue, as southern California pushed for the inclusion of another ghost town in the Mojave Desert (see my next post). After some compromises the state legislature elected to declare a "gold rush ghost town", and a "silver rush ghost town". Bodie received its designation in as the gold rush town in 2002.
Saturday, December 5, 2009
Nothing happened, of course. My life has not been THAT interesting yet. But it got me thinking. Grizzly Bears have been extinct in the state since the 1920's. The remaining black bears have not caused a single fatality in Yosemite since the park was established (they have been a lot nicer to us than we have been to them). Despite a few newsmaking exceptions, cougars have not been much of a threat to humans. We have a better chance of dying from bee stings and car accidents. This has not always been the case in California.
Prior to 12,000 years BP, our state would have been an intimidating place. Packs of Dire Wolves and American Lions roamed our prairies, seeking their prey from among the herds of horses, camels, antelope, bison, elk, mastodons, and mammoths. Short-faced bears, larger than grizzlies and polar bears, would have at least considered having you for lunch. In more forested and brushy areas, the large plant-eaters faced a threat from one of the most intimidating predators of all, the saber tooth cat (Smilodon californicus).
The largest cougars today weigh in at 200 lbs or so. The saber-tooths were more like 700 lbs or more! They were heavily built, especially in the front, giving them in advantage in stealthy ambushes. Their dagger-like serrated fangs could be 11 inches long. They didn't waste time chasing their prey, they jumped, bit, and waited for the victim to bleed to death. Evidence suggested they worked in social units, somewhat like wolves (many specimens show evidence of recovery from broken bones that would have led to the death of solitary predators).
The La Brea Tarpits in Los Angeles provide one of the richest records of the Ice Age predators to be found anywhere in the world. Trapped plant-eaters attracted large numbers of predators to the pools of sticky tar, and the hunters were trapped as well (something like 90% of the specimens recovered are predators). Portions of 1,200 saber tooth individuals have been found so far, allowing for all manner of population variability and growth studies to take place.
From about 1.6 million years until just 10,000 years ago, the sabertooths and other large animals dominated the ecosystem of California. Their disappearance is linked to severe climate changes in the aftermath of the most recent ice age, or to overhunting by newly-arrived humans. The issue of the North American megafauna extinction is one of the more intriguing mysteries of the present day.
The Smilodon californicus was selected as the state fossil of California in 1973, beating out the trilobite species Fremontia fremonti for the honor. I understand the desire of many of the paleontologists to have a trilobite named the state fossil, but I must say I get a lot more oohs and ahs from elementary students when they see my Smilodon skull during their visits at the department. They are absolutely fascinated to find that the animal once lived, quite literally, in their backyards. So do I!
For more info:
Friday, December 4, 2009
California is a landscape of superlatives and extremes: the highest and the lowest points in the lower 48 states (Alaska: why do they leave her off these lists??). It has the hottest and driest deserts in North America, less than a day's drive from a contender for one of the snowiest places (Bear Valley once got 70 feet of snow in one year). We also have the oldest, tallest and biggest living things in existence, the Bristlecone Pine, the Coast Redwood (Sequoia sempervirens), and the Giant Sequoia(Sequoiadendron gigantea). The latter two of these trees are the California State Tree. Confusing? It turns out that the state legislature established the "native Redwood" as the state tree in 1937. But they didn't define what the "redwood" was: it took a decision by the state Attorney-General in 1951 to declare that both trees were the state tree. This was confirmed by the legislature in 1953.
The Coast Redwoods are the tallest trees on the planet, with the current record-holder reaching 379 feet. They grow in the central and northern Coast Ranges, from Big Sur to just beyond the Oregon border. The durable wood is highly valued and lumbering has been going on for more than a century, so that only about 4% of the original old-growth forest remains in California. Efforts to preserve these remaining tracts have at times been controversial, but several beautiful national and state parks protect some of the remaining trees.
The Giant Sequoia is a related species that exists today in 60 or so groves in the middle elevations of the western slope of the Sierra Nevada. These trees, though shorter (270 feet or so) are the largest living things in existence. The trees have massive trunks, sometimes more than 50 feet across, and the largest contain in excess of 50,000 cubic feet of lumber, enough to build 5 homes. The wood is too brittle for such use, and instead entire groves have been cut down to produce...grape stakes and pencils. Nearly all the remaining groves are now protected in state and national parks/monuments.
A third species, the Dawn Redwood survives in China, in a single grove of no more than 5,000 trees that was discovered in 1944, and described in 1948. It had been thought to be extinct in the Miocene epoch.
Although these trees are biological entities, they have a geologic aspect as well, that I discussed in a post some time ago. In short, the Sequoias and Redwoods have existed as a genus for 200 million years or more and once existed in groves across North America, Europe and Asia. The trees of Petrified Forest National Park were probably a related species, and I have this wonderful image in my mind of dinosaurs wandering among the giant trees. Yellowstone National Park has a series of Sequoia forests preserved in stone as well, dating to 30-40 million years ago.
Other species of redwoods were apparently wiped out elsewhere in the world by climate change, especially the Pleistocene ice ages, but in the Sierra, they survived, barely, by propagating up and down the gentle western slope of the mountains as the climate alternated between glacial and interglacial periods. Some pollen work suggests they may have been on the very verge of extinction, but luckily for us they survived, and now are appreciated as the largest living things on the planet. I suspect the Coast Redwoods survived the ice ages protected by the moderating effects of the nearby Pacific Ocean.