Monday, February 29, 2016

The Age of a Mountain versus the Age of (the rocks of) a Mountain: Arriving in Death Valley National Park

Death Valley is the largest national park in the lower 48 states, and in fact is bigger than several states. It preserves some of the most spectacular corners of the Basin and Range province, a region that extends from eastern California, all of Nevada, and half of Utah. The park includes the lowest place in North America, the hottest place in the world, some of the greatest relief in North America (the difference between the highest and lowest points, over 11,000 feet), and some of the rarest and most endangered animals (the pupfish and others). And awe-inspiring scenery!

We entered Death Valley from the west, driving over the Darwin Plateau at the south end of the Inyo Mountains. Just beyond the summit we stopped briefly at the Father Crowley Vista Point, which overlooks a deep desert valley that isn't Death Valley. It's Panamint Valley, another faulted basin only a bit less deep than Death Valley itself. The setting sun highlighted the rocks exposed across the valley in the Panamint Mountains. Thousands of feet of limestone and sandstone were visible, exposing evidence of more than 100 million years of quiet deposition of mud and sand on the western margin of the North American continent during the Paleozoic Era
It was a good moment to draw a contrast between the age of a mountain range and the age of the rocks exposed within the mountain range. These are two different things. The rocks of the Panamint Mountains formed over a  period of many hundreds of millions of years, but the mountains themselves are very young (geologically). Lava flows on top of the now separated mountain ranges show that they were once connected, and that the valleys could only have formed in the last few million years. The Panamint Mountains are one of the youngest mountain ranges on the planet! By comparison, the Rocky Mountains are around 50 million years old (with some recent rejuvenation), and the Appalachians are 300 million years old (with a complex story that played out over tens of millions of years). India began slamming into Asia 40 million years ago, forming the Himalayas. The earliest Hominids, had they cared to, could have seen Death Valley before it became an actual valley.

As the shadows lengthened, we crossed Towne Pass at 4,956 feet (1,511 meters), and descended the long grade to our our sea level camp at Stovepipe Wells. We had reached the actual Death Valley. Would there be geology? Would there be flowers? Stay tuned!

Saturday, February 27, 2016

Cartoons Come to Life: The Value of Field Studies at Red Rock Canyon

I spend a lot of time in classrooms drawing cartoons. Lots of them, diagrammatically representing folds, faults and stratigraphy, trying to communicate to my students how these structures tell the story of the Earth. The problem for many of my students is that these are just cartoons. Cartoons on Saturday mornings (do ANY of you remember when that was the only time one got to watch cartoons?) do represent life in a way, but only if you have a real life to compare them to. And that's the problem for many students these days. They have no real-life experiences in the outdoors with which to compare these drawings.

And thus, the value of a field studies course. There is nothing quite like having the privilege of standing beneath a cliff, enjoying and appreciating the scenery, yes, but also being able to understand the story it tells. Our trip to Death Valley a few weeks ago included a fossil hunt at the first stop, but our second was a site where basic principles of geology stand out in stark relief, without a need for a chalkboard cartoon (I forgot the chalkboard this trip anyway). We had arrived at Red Rock Canyon State Park in the Mojave Desert. Just stepping out of the vehicles presented us a cliff face that was a physical representation of the diagram at the top of the post, a series of brightly colored layers of sand, siltstone and volcanic tuff transected by a fault.

The order of the layering provides a fine example of "superposition", the principle that layered rocks are stacked oldest to youngest, unless they have been overturned. This is one of the earliest principles of geology, described originally by Nicolas Steno in the 1600s. Looking east along the cliff we could also see the physical manifestation of another Steno principle, that of original horizontality. Most sedimentary environments produce horizontal strata (think floodplains or lakes, or shallow seas). If layers are tilted, some kind of force has acted on them, and being here in southern California, faults might be at fault.

A discussion of these basic principles was followed by a short "mapping" project. We weren't quite to the proficiency of working with maps, but the students set out to propose how they would organize the layers into formations and members that could be used to tell a logical story as to how these rocks could have come to have the structure and appearance they have today.

Red Rock Canyon does have a fascinating story as it turns out. The red and brown layers, called the Dove Springs Formation, record deposition of silt and sand in river floodplains and ephemeral lakes between 12.5 to 7.5 million years ago. The semiarid savanna environment supported a diverse ecosystem that included extinct elephants (gomphotherium), ancestral rhinos, three-toed horses, giraffe-like camels, saber-toothed cats, and bone-crushing ancestors to the bears and dogs. There are also numerous smaller fossils like ancestral skunks, alligator lizards, and shrews, with a total plant and animal species count of more than one hundred. The ecosystem suffered the occasional catastrophe as it was buried by volcanic ash. Basaltic lava flowed across the region.
One of the student's discoveries was a somewhat less visible fault that shifted the layers. It was a great introduction into the mind of field geologists, seeing the world the way earth scientists do. It was an interesting spot, but there were many more to come on the road ahead.

Speaking of roads and cartoons come to's the Roadrunner (pic is actually from Joshua Tree National Park)....

...and Wiley E. Coyote. Despite living in the most desolate driest place in North America, it looks like this one has actually caught a few roadrunners! Seriously, this coyote lives only a few miles from Badwater, the hottest and lowest part of Death Valley.

Wednesday, February 24, 2016

Another Moderate Earthquake in Central California: 4.9 the Great Valley???

The Wasco 4.9 earthquake, as recorded at Modesto Junior College

California has been shaken by another near-magnitude 5 earthquake, and this one is a bit odd. It hit in the Great Valley, one of the few places in California NOT known for having faults and earthquakes. It occurred near the south valley town of Wasco, and had a magnitude of 4.9, along with a couple of aftershocks as high as magnitude 2.6. The first motion solution suggests right lateral strike-slip motion in the same orientation as the San Andreas fault, which lies to the west in Coast Ranges.

Not the kind of place one expects to see fault zones...
The Great Valley indeed has few active faults, but the Bakersfield region is a definite exception. The south end of the valley is a structural nexus in California where five geologic provinces come together. The region is riddled with structures related to movement along faults like the San Andreas, the Garlock, and the White Wolf, which generated a magnitude 7.6 magnitude earthquake in 1952 that killed a dozen people. A few faults are mapped close to Wasco, including the Pond-Poso Creek fault (see the California State interactive fault map at
I have to admit that my first thought upon seeing quake reports was that it resulted from waste disposal related to fracking . The more I've looked though, the less I am concerned about this possible cause. The quake was deep, around ten miles, and has motions consistent with a tectonic origin. There are no reports of damage that I have seen.

The U.S. Geological Survey event page for the earthquake can be seen at

Tuesday, February 23, 2016

Picture of My Hand. Oh, and Some Sun Dogs with an Ice Halo

I was out at the San Joaquin National Wildlife Refuge this afternoon, checking on what migrant birds are still hanging around as we approach spring. I noticed some sun dogs in the western sky, and snapped a shot or two, but the bright sun was causing lens flares that were messing up the shots. It finally occurred to me to put my hand in front of the sun and suddenly I saw something I've never seen or noticed before: a 22° ice halo around the sun.

The sun dogs (also called mock suns or phantom suns; scientists call them parahelia) are caused by the refraction of sunlight through hexagonal ice crystals in the upper atmosphere. The rainbow colors in the sun dogs themselves happen because of the prisming effect of the crystals.

Either that, or I have summoned forth the twin solhundes (sun wolves) of Norse mythology...

Monday, February 22, 2016

There's a Reason California is a Nice Place to Live, Drought and All

This post is directed (gently) at those who like to disparage those of us who choose to live in California, that dystopian socialistic state on the West Coast of North American continent. There are problems here like anywhere else, but there are moments of pure magic too. Those moments last days sometimes, even weeks or months. Take winter for instance. According to the calendar, it's still winter, and in many parts of the country people are still digging out of the snow. We have snow in California, at least when the drought is not so intense. We can visit our snow any time we want! And then we can go back down into our green valleys and soak up some sunshine.

We actually have two kinds of "snow". The other is falling off the almond trees about now, as the they bloom and set fruit. Yes, that's happening now. I left a week ago to go take a field class to Death Valley, and when I got back it seemed like the entire Great Valley was awash in white blossoms. It was a startling change.
Death Valley was having one of the greatest flower shows in decades, but coming home I realized that we are going to have a nice flower show in our valley and foothills this year as well. One of the best of our local wildflower spots is the Red Hills Area of Critical Environmental Concern (how is THAT for a name?). The little mini-wilderness in the Sierra Nevada Mother Lode protects a unique area of serpentine soils that have little in the way of invasive grasses, and lots of endemic flower species. It's on the verge of exploding into a living kaleidoscope of color. I'd be lying to say there were lots of flowers today, but there were a few dozen early blooms of Monkey-flower, but in a few weeks there will be thousands upon thousands. They'll be followed by orange Golden Poppies and blue Lupines shortly after. I'll keep you posted!

Sunday, February 21, 2016

Treasures From the Earth in the Great Valley: What the heck was living here?

Standing on a barren hillside east of Bakersfield, one looks over a dry landscape peppered here and there with oil drilling rigs. Because of the recent rains, the grass is green, but roasted brown is normal for these badlands. It's hard, standing in this desert, to visualize that this was once a shallow sea, a sea that was filled with life. 15-16 million years ago, there were ancient species of clams, snails, fish, rays, sharks, dolphins, seals, sea lions, and whales. The nearby coastal plains were populated with horses, camels, primitive species of elephant, and predators who were the ancestors to today's large felines and canines.
The Great Valley began existence as a forearc basin between the volcanic range of the Ancestral Sierra Nevada, and the vast Cascadia trench and subduction zone that formed the western boundary of North America for much of the last two hundred million years. The shallow sea collected sediments from the rising mountains, and the basin floor subsided beneath the weight of the strata. Ultimately, the sediments in the basin reached a thickness of ten miles in the area around Bakersfield. Since a great deal of organic material was present in the rock, oil and natural gas accumulated in traps beneath folds and faults.
The are a few spots were animals died in profusion, or where their carcasses accumulated. One of these is exposed at Sharktooth Hill, a privately owned area where a layer, the Round Mountain Silt, included a 3-4 foot thick horizon full of fossils (collecting is allowed with a fee). A few other slopes provide the occasional sharktooth or bone fragments. The origin of the plentiful fossils has long been a source of speculation. Some of the most reasonable explanations involve "red tides", accumulations of algal toxins in the food chain, and turbidity currents, which may have gathered carcasses in specific areas of the seafloor.
There's no experience quite like finding a fossil for the first time. What child hasn't dug in his or her backyard in the hopes of finding prehistoric creatures? The small bit of fish vertebrae or the diminutive shark tooth might well be a Tyrannosaurus rex skeleton for all a student is concerned. It's a good way to start a field studies course.

We didn't find that gigantic tooth at the top of the post, by the way. There are folks who spend days and weeks digging in the ground for specimens. We met a gentlemen who has worked the site for three months. The tooth may very well be from a Carcharodon megalodon, the legendary Great White Shark relative that reached lengths of as much as 60 feet (18 meters). And no, they don't still exist in today's oceans, despite what the Discovery Channel tells you. Isn't a Great White enough in terms of terror?

Thursday, February 18, 2016

An Important Island in Southern California Gains Permanent Protection

San Gorgonio and the San Bernardino Mountains from the vicinity of Idyllwild
There's an island in Southern California. There are lots of islands, actually, and some, like Catalina and the Channel Islands, are famous. They are also surrounded by water. This island is a bit different. Instead of water, the island is surrounded  by lowlands and urban development. The island is the San Bernardino Mountains, one of several mountain ranges that form a ring around the Los Angeles Basin and Inland Empire.
 The range includes the tallest mountain in Southern California, San Gorgonio Peak (11,499 feet), and a high alpine ridge that has a dozen or so peaks exceeding 10,000 in height. It has the southernmost aspen grove in North America, and evidence of the southernmost glaciers (even a few small glacial lakes). The ruggedness of the range has precluded the kinds of developments and "improvements" that have spoiled many other beautiful places. The Whitewater River, with its headwaters near San Gorgonio Peak, flows a vertical distance of two miles to the desert floor, unimpeded by dams or other developments. Few such rivers are left in the state (it's probably fair to say that a dam would have been foolhardy, as the river crosses the San Andreas fault, and engineering would be very...iffy).
Photo by Mrs. Geotripper

The mountain range is a treasure. In my youth, I honed my hiking and camping skills in these mountains, and from them I learned to love topographic maps. It pains me that I don't have digital images of the sights I saw in these peaks forty years ago when I regularly backpacked in and out of the canyons and across the mountaintops. One of my most vivid teenage memories is a hike I took into the headwaters of the North Fork of the Whitewater River. The camp was on a terrace above the creek, and there was an expansive view eastward into the desert around Palm Springs. As the sun set, we could see thunderheads rising in the far distance, and the nighttime was punctuated with flashes of lightning. I had never felt so isolated in my life, and that is not a common feeling for the people of SoCal. It was exhilarating, and I loved every moment.
Source: National Park Service
I want to tell a story. The Channel Islands off the coast of Southern California were once much larger. This was because of the lowering of sea level by the glacial ice ages at various times during the last two million years (so much water was locked up in ice on land worldwide that sea level dropped several hundred feet). The islands were never actually connected to the mainland, but the distance between them was much less than it is today. Somewhere in that stretch of time, a herd of Columbia Mammoths (or a pregnant one) was panicked into the ocean surf (or perhaps they smelled food on the islands), and they (or it) swam the 5 or 6 miles to the island. Elephants come equipped with a snorkel; they're good swimmers. They thrived on the island, but the ice age ended. Sea level rose, first shrinking the size of the island, and then dividing it into four much smaller islands. Food became scarce. The mammoths continued to produce offspring, but it was only the smaller animals that could survive in the restricted environment. They could get by on less. Because the runts survived, they were the most successful at passing on their genes. The Columbian Mammoths, some of whom stood as tall as 14 feet at the shoulder, got smaller.
Source: U.S. Geological Survey, via

And smaller. Eventually, a race of pygmy mammoths (Mammuthus exilis) evolved. Some of the adults stood no higher than 7 feet at the shoulder, and weighed one ton, instead as much as ten. Eventually though, even small size wasn't enough. They became extinct about 12,000 years ago.
There is a lesson here, of course. All good stories have them. The environment that supported the mammoths became smaller and more limited, inexorably, until it was strained beyond recovery. The animals disappeared, and we are today deprived of what must have been a fascinating creature. Think about what has happened to Southern California in the last century. The population has expanded to tens of millions of people, and the wild lands that surround the urban valleys have become smaller and more isolated. The ecosystem is breaking down, as animals are no longer able to cross urban corridors to find others of their kind. They retreat farther into their shrinking habitats, and populations plummet. If there is no intervention, they will simply disappear. The bighorn sheep, mountain lions, bears, foxes, and condors will all be gone.

But this post is not pessimistic. Far from it. This is about a piece of tremendously good news that came to pass this week. For years, California Senator Feinstein has been promoting the idea of several national monuments or parks in Southern California. The political gridlock in Congress has prevented anything from being done, but President Obama has used his authority under the National Antiquities Act to declare three new national monuments. Two of them are in the Mojave Desert, in the Castle Mountains, and in the landscape between Joshua Tree National Park and the Mojave National Preserve. The third, Snow to Sand National Monument, brings protection to the highest ridges of the San Bernardino Mountains to the desert floor at Morongo, and even more importantly, linking the mountains to Joshua Tree National Park. This has the effect of bringing permanent protection to a very scenic wilderness area, but even more importantly, producing an intact ecosystem that will give declining wildlife populations a fighting chance to survive, especially as our global climate warms up.

By preserving an unbroken habitat from just above sea level to 11,499 feet, there were be room for upward migration of animal and plant species as the lower levels become hotter and drier. Few places in the world offer such a range of available habitats. There is so little left, so I'm glad to see these efforts to protect such a fascinating region. The mountains of my youth!

Wednesday, February 17, 2016

In Death Valley: What a Difference a Year Makes, What a Difference a Decade Makes

February 13, 2016
This spring is shaping up to be an extraordinary year for wildflowers at Death Valley National Park. There have been a series of wet storms (by Death Valley standards) and they have been spaced in such a way as to provide the best possible conditions for germination and growth of plants. Those who have visited Death Valley under "normal" conditions will have memories of barren rocky alluvial fans, naked slopes of bedrock, and a distinct lack of greenery. That most certainly is not the case this year. The wildflower show has started early, and it is robust.

We were in Death Valley over the weekend for our annual geology field studies trip, and one of our traditional stops is an exposure of the Pahrump Group of rock layers at the base of Jubilee Pass about twenty miles south of Badwater. The rocks record the ripping apart of the ancestral North American Continent around a billion years ago, and they are interesting no matter the season. The black hill is composed of Beck Springs formation, a dolomite deposited in a fault trough under tropical conditions. The orange rocks are the Kingston Peak formation, a rock that includes probable glacial deposits. In a tropical, even equatorial setting. These rocks record what may have been the planet's most intense glacial episode, a period when much of the Earth was covered by glacial ice (it's called the Snowball Earth Hypothesis).

But on Saturday, the hills and slopes were alive with Desert Gold and Verbena. And there were lots of green sprouts, promising even more growth in coming weeks. Officials are suggesting this might be one of the ultra-rare "superblooms" that occur over decades rather than years.
February 2015
Contrast the same spot as it appeared last year at the same time. We found a few flowers hidden in the washes, but clearly there was no explosion of life in that dry year in a place that is drier than anywhere else in North America.
February 2005

I've been privileged to see just a handful of extraordinary growth years. The only one I have digital images from was in 2005. It provides a nice comparison to what is happening in Death Valley right now. That year was a real challenge as we faced heavy rain and wind for most of the trip. The portrait below illustrates my morning observations that year. I'm thankful that we had perfect weather this last weekend.

I'm hoping to make a special trip out there in a few weeks to see how things are progressing.

Tuesday, February 16, 2016

Magnitude 4.8 Earthquake (and 4.3 Aftershock) in Eastern Sierra Nevada near Big Pine

I wandered past our department seismometer (at Modesto Junior College in central California), and noticed some disturbances that didn't look like the record of students jumping up and down. They indeed turned out to be a pair of moderate earthquakes of magnitude 4.8 and 4.3 with an epicenter about 7 miles (10 kms) WNW of Big Pine, a small village in the Owens Valley east of the Sierra Nevada. A 4.8 magnitude can be a pretty sharp jolt, but this is a sparsely populated area, so I don't expect to hear of much in the way of damage.

The epicenter is just north of the Palisades Group of peaks on the eastern boundary of Kings Canyon National Park. They are the snowy glaciated peaks in the picture above. Big Pine is just to the left of the picture on the valley floor.
4.8 magnitude main shock

The fault that produced the quake shows right lateral strike slip motion. This means that the two sides of the fault moved sideways relative to each other, with the southwest side of the fault moving northwest. Since the Owens Valley is a fault graben, one might assume that the fault motion should have been vertical, i.e. lifting the mountains or dropping the valley, but the Sierra Nevada as a structural block is moving northwest relative to the rest of the continent, so this quake is consistent with that motion.
Sierra Nevada as a "microplate" moving northwest. Big Pine is labeled BP. Source:

The regional is seismically active. One of California's great historical earthquakes had an epicenter a short ways to the south at Lone Pine. The 1872 event had a magnitude estimated to be  as high as 7.9. The quake killed 27 people, nearly a tenth of the population of the village at the time. Ground ruptures extended from Owens Lake to north of Big Pine.
The 4.3 magnitude aftershock

Our seismometer is a simple classroom instructional model (from Wards Scientific), but we get good results with local quakes of moderate magnitude, and larger quakes worldwide.

The U.S. Geological Survey event page for the magnitude 4.8 quake can be seen here:

Extraordinary Times in Death Valley National Park

There will be plenty more coming up, but here is just a taste of what it is like in Death Valley National Park right now. The pattern and amount of rainfall in the park has been a "perfect storm(s)" to bring about an astounding wildflower show. We spent last weekend in the park, and although the flowers were incredible, the green sprouts suggests there will be much, much more in coming weeks. I haven't seen a flower show like this since I began blogging in 2008. In 28 years of February visits, I recall only 2005 and 1998 being comparable for early blooms. I'm looking forward to sharing more (plus some geology too!) in coming posts once I've had time to unpack and relax a bit.

Sunday, February 7, 2016

These Lands Belong to All of Us - Domestic Terrorism and National Wildlife Refuges

Beauty and ugliness...

A Meadowlark is singing in the's early February in California which actually means that spring is practically here. In other places, biplanes are spraying pesticides and fungicides, beekeepers are setting out hives in the almond groves, and fields are being plowed and readied for planting. About 95% of the floor of the California's Great Valley is being readied for crop production, with some hopes that the larger snowpack will allow irrigation allotments for the first time in a number of years.

But not here. I spent the afternoon on a deserted road that traveled around the Tule Elk habitat at the San Luis National Wildlife Refuge. Nothing human was happening here. On this old floodplain of the San Joaquin River the native grasses were sprouting bright green shoots, and the elk were grazing in the distance. The Salt Slough was flowing, and the water was uncharacteristically clean. Dozens of Meadowlarks were singing their alluring songs, and numerous hawks, the Red-shouldered, the Red-tails, and Harriers were patrolling, looking for ground squirrels emerging from their burrows.
Tule Elk at San Luis. There were just two left in the 1880s

On this small patch of valley floor, environmental managers of the Fish and Wildlife Service are trying to restore a bit of the valley to something that resembles the land the once provided food and shelter to millions upon millions of birds, mammals, reptiles, amphibians and many others. The Great Valley was once America's Serengeti Plains, one of the richest wildlife habitats on the planet.
Black-necked Stilts

I haven't said much about the criminal drama that unfolded last month at the Malheur National Wildlife Refuge. I was waiting for some kind of resolution. Four of the terrorists are still holding out at the refuge wondering where all their brave "patriot" friends are, so the situation remains unresolved. But sixteen of the gun-toting thugs are under indictment, and LaVoy Finicum lies dead in the ground, a self-appointed "suicide by cop". Some people are calling him a patriot and a martyr. I call him a common criminal who ran a roadblock and then tried to draw a gun on law enforcement officers.
I believe it is a juvenile Red-tailed Hawk

This isn't opinion, this point of view is a matter of law. People decided to take up arms against a duly elected representative government and tried to effect political change with guns. These were criminal acts that followed years of threats and intimidation. These people can try to pretend they were following some bizarre interpretation of the Constitution, but the Constitution makes clear that the powers of government do not lie in the hands of people with guns trying to steal public land for their own private use.
Grasslands at San Luis. Brewers Blackbirds in the tree in the distance.

I'm not sure these people even understand the principle of civil disobedience that brought about the Civil Rights Act and the Voting Rights Act. In that era people broke the law on purpose, but they expected to be arrested and were ready to be imprisoned to bring about legal changes in the country. They didn't carry heavy weaponry and threaten to kill public officials. They instead paid a heavy price themselves, even to the point of death in too many cases.
A Loggerhead Shrike
But most of all, I'm enraged that these people think that they somehow deserve unfettered free access to land they have no claim to. The states of the American West ceded control of these lands as a condition of statehood. They received trust lands as part of statehood, and almost without exception those state lands are wasted, denuded, and closed to public access (read the story here from High Country News). The efforts of the federal government to administer the remaining public lands has been a patchwork of success and failure, but on the whole there is a recognition that these lands belong to all of us, and should be treated that way. Sometimes the use involves resource extraction and profits for certain groups and corporate entities, but much involves the public good.

Salt Slough, a tributary to the San Joaquin River

Private landowners are often responsible and are responsive to efforts to preserve part of their holdings for wildlife. But they can't be expected to understand and act on the fact that their portion of the landscape is a small piece of a wildlife network with connections from the far northern Arctic to the tip of South America. Only the federal government can do this, and its role in wildlife management is both legal and supported by the vast majority of the citizens of our country. Only the federal government can provide protection for the breeding grounds of migratory geese and cranes in the far north and at the same time provide wintering grounds in California and other parts of the southwestern states. Only they can provide resting places for the birds at refuges between the two extremes of the migratory routes. And only the federal government can enter into diplomatic agreements to protect animals whose migratory pathways carry them over international borders.

Great Blue Heron on Salt Slough

Federal management of grazing lands has not been perfect, but there are many examples of cooperation between different stakeholders in the debate. The vast majority of ranchers are law-abiding citizens. But those who decide to take up arms against the government must be dealt with proportionately. Anyone who threatens the life of another, and acts on that threat needs to be in prison, and their weapons taken away. The moment these criminals brandished guns they lost their place at the table.

Double-crested Cormorants

It was a beautiful day today at the San Luis National Wildlife Refuge. I could wander over the grasslands and imagine how this valley once was. So much has been lost, but much still remains, and it was both a privilege and a right to be there on this really early "spring" day. I salute those who work at these refuges and who are fighting to do the right thing, sometimes in the face of threats and intimidation. Thank you for the good work that you do.
Beaver or Muskrat?

The San Luis National Wildlife Refuge protects the floodplain of the San Joaquin River between Turlock and Los Banos in California's Great Valley. There is an excellent visitor center, and a number of available auto tours and hiking trails. For more information, check out their web page: