Of Vooks and Blooks

I offer my apologies in advance for what follows...

I thought I heard a discussion of some weird new kind of "vook" on public radio the other day, and finally ran across a written account of video-book hybrids in this article in Salon.com. I can see the usefulness in such a monster if some kind of complicated process is being taught, but I am less enamoured of the idea if it is going to be a low-cost drama production. I get lots of that on the cable channels.

It reminded me of a discussion I had the other day with someone who doesn't want to be associated with the writing disaster that follows. We were talking about the nomenclature for the project I just finished on the Colorado Plateau. Over a year's time, the series of blogs had grown into a narrative with the length (if not the style) of a small book. What should such a thing be called?

We immediately thought of "blook" and congratulated ourselves on our creativity and originality but a quick google search confirmed the that term has existed since at least 2002. Oh well. Just the same we realized that people who write blooks would have to be called "blookers", and if the authors are German women, they would be "Frau Blookers" (frenzied neighing of horses breaks out*).

Our second choice for the name of a blog-book hybrid would be a "boog". I liked it, but a google search revealed that a boog had all kinds of dark and gross meanings related to nostrils and drugs. So that won't work so well, but so many things could have been right about the word. When we said we needed to "boogie", folks would think we were really cool and all, and not going home to chew on Cheetos and stare at a computer screen. The problem with "boogs", books written as a series of blog posts, is the lack of continuity and style. Such projects need the help of an editor or even an editorial board, a "boogie-board" as it were.

Maybe an interesting idea. It ultimately can't work though, because the authors of boogs would of course have to be called..."boogers".

Ok, back to geology...

*If you don't know this movie reference, you have to go study Mel Brooks and satires of old monster movies

Do Big Earthquakes Cause Tremors Elsewhere?

With the spate of large earthquakes worldwide, some people have asked if large earthquakes can set off smaller earthquakes elsewhere. In short, the answer is yes, but the big earthquakes don't make other earthquakes; they may help trigger earthquakes in places where stresses are close to the breaking point anyway. These smaller quakes usually occur within a few hours of a major tremor. But there are some odd complications that are now being recognized.

Some new research, reported in NatureNews, suggests that large distant quakes can weaken other fault zones and cause activity months later. This assertion is supported by the fact that the period of 2005-2007 following the devastating magnitude 9 Sumatra-Andaman quake (the tsunami killed nearly a quarter of a million people) had the largest number of large earthquakes than any comparable period since the early 1900's.

The abstract for the research article can be found here (the entire article requires a fee). The full article: Taira, T., Silver, P. G., Niu, F. & Nadeau, R. M. (2009). Remote triggering of fault-strength changes on the San Andreas fault at Parkfield, Nature 461, 636-639.

The photos today show the San Andreas fault on the Carrizo Plains south of Parkfield, and the Landers fault in the Mojave Desert. The 1992 quake on the Landers fault (mag. 7.3) set off tremors at Parkfield months later.

The Keeler Earthquake Swarm

The U.S. Geological Survey (and my department seismometer) is reporting a vigorous swarm of small and moderate quakes about seven miles south of Keeler, California. The swarm has included two 5+ magnitude shocks, and at least 22 events between magnitude 3 and 5. Smaller events number in the hundreds.

Keeler is a small village along the former shoreline of Owens Lake at the south end of the Owens Valley. The pictures provide some context: the Owens Valley is the first of the Basin and Range Province grabens east of the Sierra Nevada, with the White/Inyo Mountains forming the east side. The top picture shows the Sierra crest, including the peaks in the vicinity of Mt. Whitney, the tallest mountain in the lower 48 states. The bouldery Alabama Hills and the town of Lone Pine are in the bottom of the valley, center-left, and the Inyo Mountains form the right-side skyline. With the valley floor at 4,000 feet and the surrounding mountains ranging up to 14,000 feet, the valley is twice as deep as the Grand Canyon. Although the Owens River flows through the valley (sort of), it is a faulted graben, not a river-cut valley.

The second photo (from the same vantage point on the Cottonwood Lakes road) shows Owens Lake, the south end of the Inyo Mountains, and the domes and craters of the Coso Mountains Volcanic Field on the right. Owens Lake is one of the pluvial ice age lakes that formed when glacial meltwater from Sierra glaciers drained into the desert. Unlike most of the dry lakes across the Basin and Range, Owens Lake actually had water until the 1920's. Los Angeles diverted the streams that flowed into the lake and sent the water south through a massive aqueduct to the growing city. Keeler was a depot for silver and lead being mined high in the Inyo Mountains at the Cerro Gordo Mine in the late 1800's. Ores were carried down to the town by aerial tramway, and then loaded on a steamship to cross the lake to railroad station.

The epicenters of the swarm would be in about the center of the second photo. Why are there quakes here? As noted before, the entire valley is a fault graben, so quakes are not at all unusual. One of California's largest historical earthquakes, the 1872 Lone Pine earthquake (mag. 7.8 or so) happened just north of here. Swarms have happened in the local region in the past, including some magnitude 5 events in the 1990's.

The Coso Volcanic Field lies just to the south. A collection of basalt flows and rhyolite domes, it was last active around 40,000 years ago, though a few cones may be younger.

UPDATE: not of the earthquake, but of the Coso Volcanic Field. It might be an actively forming metamorphic core complex! In 2 to 4 million years, the detachment surface may be exposed. I always enjoy learning something I didn't know before...

UPDATE #2: Loads of info on the quake swarm on the SCSN Pages here. The largest quakes are showing right lateral focal plane solutions, which is in keeping with the regional structural trends on the Owens Valley floor. This strongly suggests to me that the quakes are tectonic and not related to any kind of volcanic activity (but I'm not claiming expertise in the matter).

UPDATE #3: Reports of sand boils on the Owens Lakebed (see the comments) have been confirmed by the SCSN and USGS office in Pasadena (personal communications, no link).

UPDATE #4: See down in the comments for a correction on the history of Keeler from Roger Vargo, who is the sometimes caretaker at Cerro Gordo. Thanks for the correction, I was operating off the memory of a field trip from 25 years ago.

Time Beyond Imagining: A "Brief" History of the Colorado Plateau

Please forgive me for filling the feeds with such a long post, but I wanted to pull together an annotated list of the blog posts of my just completed journey through the geological history of the Colorado Plateau. It turned into a massive project that lasted more than a year, and included seventy different postings and more than a hundred photos. Don't feel compelled to try reading it, but I hope you enjoy it if you do. If it lacks precise continuity and style, remember that I had no idea how it would end when I started it and I had no editor! I've been taking students on the plateau for twenty years, and it has proven to be one of the best places on the planet to learn earth history.

Time Beyond Imagining, the first post back in June of 2008 introducing the concept that would guide the entire series. I had no idea what I was getting into!

Time Beyond Imagining - An Intro to the Colorado Plateau, a first introduction to the sweep of the landscape that I would be covering through the series.

Time Beyond Imagining - The Oldest Rocks on the Colorado Plateau: The oldest rocks are exposed at only a few places, including deep in the Grand Canyon

Time Beyond Imagining - A Brief History of the Colorado Plateau, Part 2: A discussion of the 12,000 feet of sediments hidden deep in the depth of the Grand Canyon dated at around 1 billion years

Time Beyond Imagining - A Brief History of the Colorado Plateau, Part 3: LIFE!: The first appearance of complex life during the Cambrian Period

Time Beyond Imagining - A Brief History of the Colorado Plateau, Part 4: Something is Missing! Journeying up the walls of Grand Canyon through the Ordovician, Silurian and Devonian periods

Time Beyond Imagining - A Brief History of the Colorado Plateau, Part 5: Seeing Red Looking at the Mississippian Redwall Limestone in Grand Canyon

Time Beyond Imagining - A Brief History of the Colorado Plateau, Part 6: Seeing Red (Really!) We rise up through the walls of the Grand Canyon to the Permian rocks of the Supai Group and Hermit Shale

Time Beyond Imagining - A Brief History of the Colorado Plateau, Part 7: Mountains Rise: Permian rocks are exposed throughout the plateau country. We leave the Grand Canyon and explore some of these other places

Time Beyond Imagining - A Brief History of the Colorado Plateau: Old Salt I was beginning to realize that the project would be longer than I thought. We explore the formation and effects of salt precipitation in Late Paleozoic time

Time Beyond Imagining - A Brief History of the Colorado Plateau: Sand! A return to the Grand Canyon and the prominent Coconino Sandstone near the rim

Time Beyond Imagining - A Brief History of the Colorado Plateau: A Final Transgression Looking at the top two layers in the Grand Canyon and related rocks on other parts of the plateau.

Time Beyond Imagining - A Brief History of the Colorado Plateau: On to the Grand Staircase An introduction to the Mesozoic history of the plateau country, which lies outside the Grand Canyon. We start exploring the other wonderful parks out there

The Grand Staircase and the Geologic Time Scale A diagram of the Grand Staircase, the younger rocks of the Colorado Plateau

Time Beyond Imagining - A Brief History of the Colorado Plateau: Into the Triassic An introduction to the widespread Triassic rocks of the Plateau. It would prove to take a number of posts!

Mid-week Mystery Sample: What is it? A short departure to discuss the identity of a Triassic fossil from the plateau. A fairly long discussion followed!

Mid-week Mystery Sample: What is it? Heck if I actually know! I admit to my ignorance...

Time Beyond Imagining - A Brief History of the Colorado Plateau: Ash and Wood A study of the paleontology of one of our unusual parks: Petrified Forest in Arizona

Time Beyond Imagining - A Brief History of the Colorado Plateau: This Yellow is NOT Mellow The Chinle also contains mineable uranium deposits; I wade into the controversy

Leetso, the Yellow Monster A continuation of the heritage of uranium on the plateau

Time Beyond Imagining - A Brief History of the Colorado Plateau: The Real Jurassic Parks The Jurassic rocks of the plateau are responsible for much of the spectacular scenery in the region. This was the introduction

The Colorado Plateau Story: the real Jurassic Parks Follows the story of the Kayenta and Wingate formations, and three unique and little known parks: Capitol Reef National Park, and Colorado and Vermillion Cliffs National Monuments.

The Real Jurassic Parks: Navajo! The Navajo Sandstone forms some of the best photography opportunities: this was a discussion of Antelope Canyon, a beautiful slot canyon

Antelope Canyon, A Real Jurassic Park An excuse to show more pictures of Antelope Canyon!

Zion: A Real Jurassic Park First part of look at one of our "crown jewel" national parks

Zion: A Real Jurassic Park, Part 2 A hike to Angels Landing in Zion National Park

The Real Jurassic Parks: Capitol Reef (Oh, and Sheep Blogging) A return to Capitol Reef and an excuse to show off one of my favorite bighorn sheep pictures

The Real Jurassic Parks: The San Rafael Group An introduction to another group of Jurassic formations, including the all-important Entrada Sandstone. A busy semester had begun and posts were becoming sparser at times. I was realizing the project was going to take some time, and I stopped using the word "brief"!

The Real Jurassic Parks: Goblin Valley and the Entrada Sandstone One of Utah's unique and isolated state parks

The Real Jurassic Parks: Kodachrome Basin (and a great resource!) Another fantastic Utah State Park and a link to an e-book on the geology of Utah's parks and monuments

The Real Jurassic Parks: Arches National Park An intro to Arches National Park, one of my personal favorites

The Real Jurassic Parks: Arches National Park, continued. And an Eminent Threat. After several weeks I got back to work with a continued exploration of Arches, and discussed new threats to parks in the region

The Real Jurassic Parks: Where are the Dinosaurs? A look at wonderful Dinosaur National Monument and a rotten political situation there

The REAL Jurassic Parks were really Cretaceous I thought the Jurassic would provide the most posts in the series, and therefore had no idea how long I would spend in the Cretaceous. This was the introduction

The Cretaceous Parks of the Colorado Plateau: the Cedar Mountain Formation The only dinosaur dig I ever took part in was in an early Cretaceous formation in Montana, but it was related to the Colorado Plateau. This post turned into seven part story on our adventure

The Cretaceous Parks of the Colorado Plateau: the Story of a DinoDig Much of the story was trying to get there in the first place: what is geokarma?

The Cretaceous Parks of the Colorado Plateau: Every Cloud has a Golden Lining We drive through Yellowstone and arrive at the dig site

The Cretaceous Parks of the Colorado Plateau: the story of a Dino-Dig What we were looking for and why it was important. What is a deinonychus?

The Cretaceous Parks of the Colorado Plateau: the Dino-Digging Begins This is what grunt work is all about

The Cretaceous Parks of the Colorado Plateau: the story of a Dino-Dig wraps up We started finding bones!

The Cretaceous Parks of the Colorado Plateau: the Final Discovery We found a dinosaur that invariably is the last entry in a dinosaur dictionary...

The Cretaceous Parks of the Colorado Plateau: The View is Nice but Access is a Problem... Back on the plateau, we are introduced to the remaining Cretaceous rocks and two archaeological parks, Hovenweep and Canyons of the Ancients National Monuments

The Cretaceous Parks of the Colorado Plateau: Walled Cities and Tragedy More on the Canyons of the Ancients and a walled medieval-aged city...in southern Colorado!

The Cretaceous Parks of the Colorado Plateau: The Tragedy at Castle Rock Pueblo A haunted place...

The Cretaceous Parks of the Colorado Plateau: The Mancos Sea An interesting formation that some geologists curse at...

The Cretaceous Parks of the Colorado Plateau: The Green Table An exploration of the famous cliff dwellings at Mesa Verde National Park

The Cretaceous Parks of the Colorado Plateau: the Black Mesa story I wade into the coal mining controversy and get more comments than any other entry in the series

The Cretaceous Parks of the Colorado Plateau: A City in the Wilderness Life had become busy and it was a month before I returned to the plateau with a discussion of Chaco Culture National Historical Park

And The Old World Passed Away... The Geologic History of the Colorado Plateau And another month passed! I tried to find the words to describe the profound events at the end of the Cretaceous Period

Time Beyond Imagining - A not-so-brief History of the Colorado Plateau Another long gap, but I was finally talking about the last 65 million years of Colorado Plateau history with an intro to the crustal deformation that was beginning to effect the region

Time Beyond Imagining - Land of Giant Lakes A discussion of the origin of the rocks at Bryce Canyon and Cedar Breaks National Monument. I thought I was close to the end, but I was still wrong, after a full year!

Fire Down Below - a Geological History of the Colorado Plateau Another month of blogging on other things and I returned to the Cenozoic history of the region with a discussion of the volcanic activity that started to emerge on the plateau, including Shiprock

Fire Down Below II - a Geological History of the Colorado Plateau The laccolithic mountains of the plateau country

Fire Down Below III - a Geological History of the Colorado Plateau I find I have almost no pictures of Navajo Mountain despite having driven around it dozens of times...

Time Beyond Imagining: A Scrambled Landscape Cenozoic events led to a truly scrambled landscape with a mystery-of-the-day

Time Beyond Imagining: A Scrambled Landscape in Unaweep Canyon More mysterious canyons at Unaweep and Black Canyon of the Gunnison

Time Beyond Imagining: A Scrambled Landscape in Colorado An exploration of Black Canyon of the Gunnison, a canyon that shouldn't be there

Time Beyond Imagining - A Really Scrambled Landscape on the Colorado Plateau The opening discussion of one of the great plateau mysteries: why is there a Grand Canyon?

Time Beyond Imagining - Unscrambling History and the Origin of the Grand Canyon The complicated story continues

Time Almost Not Beyond Imagining: Recent Volcanism on the Colorado Plateau I thought I was almost finished, but found that much happened in the final few million years of the story. This is the story of the San Francisco Peaks Volcanic Field

Time Almost Not Beyond Imagining: Recent Volcanism on the Colorado Plateau Part 2 A look at the volcanoes in the western Grand Canyon and how they formed massive lakes in the Grand Canyon, some 200 miles long!

Time Almost Not Beyond Imagining: Recent Volcanism on the Colorado Plateau Pt. 3 The story of a stupendous rhyolite eruption at the Jemez Caldera in New Mexico

Time Almost Beyond Imagining: Who Do the Magic that Hoodoo? My favorite title for a discussion of a unique park near the Jemez Caldera, Kasha-Katuwe Tent Rocks National Monument

Time Almost Not Beyond Imagining: Recent Volcanism on the Colorado Plateau and Deep Time Although I had reached the last million years of a two billion year history, I felt a need to try and describe the immensity of geologic time, using the ruins of Bandelier National Park and the Jemez Caldera

Time Beyond Imagining - Where did the Ancient Enemy Go? The "disappearance" of the Ancestral Pueblo people is explored at Bandelier National Monument

Time Beyond Imagining: Why Can't We Touch the Venus de Milo? Once again, I thought I was done, but found a series of fascinating (to me) stories about research in the limestone caverns on the plateau. I began with a rant about preserving these wonderful caves that took us to Rome and Paris, of all places

Holy Crap, Batman! The Bat Cave is Full of it! Bat Cave in western Grand Canyon, and bat-sh*t. Lots of it, sort of

Holy Smokes, Batman, that crap is on fire! I was saving my best titles to the last, I guess. A horrific crime against science at Rampart Cave in the Grand Canyon

Of Rat Pee and Uranium and Scavengers...The Underground Story of the Ice Ages on the Colorado Plateau What the caves on the plateau tell us, and how.

Time Beyond Imagining - A Final Struggle for Life on the Colorado Plateau I imagine the death of the very last mammoth on the Colorado Plateau

Time Beyond Imagining: The End of the Story, or the Beginning? In the final post of the series, I discuss the arrival of humans on the plateau, and how humans change the land they occupy. I also tip my hat to Ken Burns and his series on "The National Parks: America's Greatest Idea". The parks are the laboratories in which I and my students study the history of the earth.

So there you go: 71 posts that tell a story encompassing 2 billion years as it is exposed on a very special part of the earth's surface: the Colorado Plateau, covering parts of Arizona, Utah, Colorado, and New Mexico. Congratulations if you ever made it through the whole thing. I never realized I was writing the equivalent of an entire book, but it was a story I truly enjoyed telling, and I also deeply appreciated the feedback that many of you provided.

Time Beyond Imagining: The End of the Story, or the Beginning?

Picking up from the ecologic trauma of my previous post, there was, in fact, a significant addition to the collection of animals living in the Colorado Plateau region in the last 10,000 years or so. It was different than any creature that existed in the region over the last 2 billion years, in that instead of living within and being adapted to the ecosystem, this creature sought to change the ecosystem to meet its own needs and desires. I am referring to humans, of course.

The first humans were hunters and nomads who made spears and atlatls to bring down large game. According to the anthropologists I know who still speak to me (they argue a lot about this stuff; it's nice to know how civil we geologists always are) they either brought about the extinction of the megafauna, or had nothing to do with the extinction. Call us the suspects or the unindicted co-conspirators in the affair, or the totally innocent bystanders. But the fact is, our cousins and forebears got to see these animals and lived among them. Some of the oldest artifacts ever found in Grand Canyon National Park are split-twig figurines of large mammals, dating to three or four thousand years ago. Even more intriguing are two petroglyphs from Utah that seem to represent a mammoth or a mastodon. They are controversial, with some saying that the rock art does not show the necessary antiquity to be the real work of an eyewitness to these extinct elephant relatives, but in any case, humans were witnesses to one of the great extinctions in the geologic history of the world, and the Colorado Plateau. And they may have caused it.

I paint with very broad strokes here, but we humans have a history of coming into a new region, using the resources, and living beyond our means until the resources are gone. Then, some kind of tragedy depopulates a region (famine, disease, invasion), so we move on and start again somewhere else.

The Colorado Plateau was first occupied by hunters and nomads who left little sign of their passing, aside from stone tools and simple shelters. Around 2,000 years ago, people began planting the food they consumed, and started building more substantial shelters and pithouses. The climate favored agriculture, and over the centuries they added new crops, including maize. The population of the plateau country expanded to levels similar to the population living there today, but by 1200 AD, something was going very wrong. A decades-long drought disrupted food supplies, and soil erosion was rampant. The architecture of their dwellings changed to a more defensive orientation, including entire villages built in high alcoves in the sandstone. By 1300 AD, pretty much the entire region had been depopulated.

Over the next few centuries, other bands of people arrived, the Navajo, the Utes, the Apache, and they lived and thrived until the region was invaded by waves of Europeans and then Americans. It seemed that everyone who arrived now was looking for something of value, be it gold, or beaver pelts, or grasslands for grazing, or coal for mining. Sometimes they found nothing and left again. If they did find something of value, they mined or grazed or hunted until the resource was exhausted, and the region would be once again abandoned.

And that is why I feel lucky to be living in an extraordinary time. Some time in the last century, there was a small group of individuals who saw a value in the land of the Colorado Plateau that was not related to money. They fought for the preservation of the best parts of the plateau country as national parks and monuments, set aside for the people of the country as a place of recreation and introspection. It was a new idea, and it was not without problems. The earliest parks were seen by their creators as tourist gold mines, and to draw tourists all manner of hotels, railroads, roads and other "improvements" were constructed. Predators were mercilessly killed off to build up deer herds. Powerful enemies were lined up to fight the establishment of every one of our national treasures, and they fought on even after parks were formed, using war and depression as an excuse to exploit valuable park resources. But through it all, the parks were preserved for the most part in a condition resembling their primeval state. They were preserved for the purpose of learning and for research.

The Ken Burns documentary "The National Parks: America's Best Idea" wraps up tonight on PBS stations. It is a stunning piece of work that explores the human journey that resulted in our national park system, an American idea that is now emulated around the world. It has been a revelation to see the story laid out in chronological order, with all the mistakes and misjudgements by people we see as park pioneers and heroes. And still, we have a park system that the American people, and indeed the world can be proud of. It is, as special unique landscapes open to all people, the best embodiment of the American ideal that all people are created equal. If you missed the first five episodes, they can be watched in their entirety on the website linked above.

And with this post I have reached the end of my chronicle on the geology of the Colorado Plateau! A project I thought would last for a month or so and include maybe a dozen posts grew into something much larger. I have no idea how many of you have followed along from the start, but I will put the posts together into a chronological unit very soon if you want to or dare to catch up. I hope you have enjoyed this journey as much as I have had writing it. I also want to thank the many people who commented and offered new information as we journeyed along.

Oh,gee... now I have to think of something new to write about!

Time Beyond Imagining - A Final Struggle for Life on the Colorado Plateau

...the massive creature wandered slowly through the dry grasslands. It had been a long hot year, something that had been all too common during the decades the animal had been alive. Foraging was difficult, and the creature was near the point of starving. The large elephant-like animal felt vaguely lonely; it was a herd creature, but it had actually been years since he had seen another of his own kind. He was aware of the pack of predators that had been following him for several days now. They too had the look of hunger, too thin, gaunt, with intense yellow eyes following every movement of the mammoth, but not quite desperate enough to try attacking such a huge beast. They could see it was weak, and they hoped for an opening.

The elephant could smell water. There was stream nearby, maybe a promise of green grass. The trickle of water lay at the base of a dangerously steep slope, but the mammoth was becoming desperate. He carefully stepped over the ledge and started down the rocky slope towards the water. Disaster! Somehow a rock slipped, and the animal lost his footing and tumbled down the slope. There was a crunching sound, and a horrific pain shot through the creature's leg. Something was terribly wrong now, and despite his struggling, he could not stand. The wolves heard the commotion. What was a tragedy for the mammoth was the temporary salvation for the giant wolves. They moved in, and in the moments that followed, the very last individual of the elephant clan on the Colorado Plateau passed into oblivion. Though they ate their fill that day, the wolves were doomed too. In these final centuries and decades of changing climate, they would find fewer and fewer of the large creatures they had evolved to consume, and they too soon passed into oblivion...

The story I've just told is entirely fanciful, with no direct basis in reality. I'm not describing some paleontological excavation, because we don't have one that is known to be the final individual of a species. But the fact is, numerous species became extinct during the last 10,000 years, and there was a final living individual mammoth. There was a final pack of dire wolves, though not at the same precise time. My little story could just as easily have included human beings who stood over the dying mammoth instead of wolves. Anthropologists argue the point.

The last few thousand years of geologic events of the Colorado Plateau are really mostly biological in nature. And to me they represent one of the saddest episodes in the entire two billion history of life in the region. In the last two million years before the present, the canyons and mountains, mesas and buttes of the Plateau looked much as they do today with one major exception. An ice age gripped the world, with a dozen or more cold periods when ice advanced across the northern tier of the North American continent. Though the ice never reached the plateau country, the climate was cooler and wetter, and forests covered what are now sagebrush flats, and sagebrush covered what are now barren desert expanses.

In this environment of rich vegetation growth, a complex ecosystem evolved, with numerous large species of plant foraging mammals, the megafauna of North America. The species that lived on the plateau included mammoths (2nd photo), mastodons (1st photo), camels, giant sloths, bisons, horses, musk ox, bighorn sheep, and mountain goats. They were preyed upon by giant American lions (4th photo), saber-tooth cats, dire wolves (3rd photo), and occasionally by short-faced bears. The lions were bigger than their African cousins, the wolves and bears bigger than their living relatives by a factor of 50%. They had evolved to take down large prey.

These species lived across the continent, and the pictures above are actually specimens from southern California. They are examples of some of the incredible discoveries from the La Brea Tar Pits, where animals were trapped by the hundreds in the black goo. The animals thrived across the land for several million years, but around 10,000 years ago nearly all of them went extinct. Their disappearance coincided with two events: the end of the latest ice age, and the arrival of humans on the North American continent. Which brought about their end? Was it a combination of factors? We don't really know yet. There have even been some suggestions by researchers that an asteroid impact affected the North American megafauna.

In any case, I feel a sense of loss that these animals are gone. Part of the adventure of visiting a national park like Yellowstone is to see the bare remnants of this megafauna: the moose, elk, buffalo and grizzly bears. What an adventure it would have been to see mammoths and other giants wandering the mesas and buttes of the Colorado Plateau!

We've nearly reached the end. I have been exploring the geology of the Colorado Plateau for well over a year now, and one final major event in the geological story remains to be explored. Next time!

Magnitude 8.0 quake in Samoa

A magnitude 8.0 quake has struck in the Samoa Islands of the Pacific. Andrew Alden at About.com is on top of this with some details here. The official USGS report is here. I only want to add that my cheap little classroom seismometer is still going off-scale more than an hour after the event. It doesn't mean that the ground is still heaving in Samoa, but instead is showing that the entire earth is reverberating as the waves pass through the entire planet, reflecting and refracting off the interior boundary layers and discontinuities. One might compare it to the gonging of a bell (the "earthquake") and the ringing tones that follow for a few moments.

You can check out the current shaking as it is recorded in California right here. Click on any of the stations to see the wave activity.