Monday, May 25, 2015
There is a lonely nondescript mountain of limestone in the barren desert east of Death Valley National Park. There is a hole at the base of the slope, the entrance to a cavern. Lurking within are prisoners, creatures that have been trapped in the cave for perhaps 20,000 years or more. They are mutants, no longer the same as their cousins who live freely just a few miles away. They are alone in the world.
That sounds kind of dramatic I suppose, but all of it is technically true. The story becomes a bit stranger when one realizes that the trapped creatures are fish. In one of the driest climates in North America.
During the Ice Ages between 1.8 million and 10,000 years ago, glaciers in the Sierra Nevada were constantly melting in their lower reaches, and some of the resulting streams and rivers drained into the desert regions to the east. The faulted valleys would fill with water and spill over into the next so that at times an entire network of lakes and rivers existed. At some point a connection was made with the Colorado River system and fish worked their way into the widespread habitats. Dozens of species thrived in the freshwater lakes.
But then conditions began to change. The climate grew warmer and the glaciers mostly melted away. One by one the lakes dried up as the rivers that once fed them turned to trickles and then disappeared. Most of the fish died out, but here and there springs or remnant lakes allowed some species to survive. The most isolated species of them all lives in this one hole, the Devil's Hole. The Devil's Hole Pupfish (Cyprinodon diabolis) is in all likelihood the rarest fish in the world. There have never been more than five or six hundred of them, and their population has reached lows of only three dozen at times. They are living at the extremes, as the water is at a constant temperature of 93 degrees. Only a few other species of pupfish can survive those kinds of temperatures (you can read about some of the other species here: http://geotripper.blogspot.com/2015/02/you-think-some-fish-you-caught-was.html ).
Their rarity explains the monitoring equipment and fencing that surrounds the cavern opening. The pool is visible from in side a caged tunnel, but the individual fish are a bit difficult to see. They're only an inch long, and the viewing platform is around a hundred feet away. I saw nothing on my previous visit five or six years ago, but this time I did.
The efforts to protect the fish almost became their undoing when a 2004 flash flood dumped the monitoring platform and other debris into their pool. Something like a third of the population was lost. The platform was gone and there was a limited amount of equipment. And, there were three squares of what looked like white astroturf in the water. I don't know their purpose, but one idea is that they may protect eggs. Or maybe someone was making it possible to see the fish from so far away.
The fish feed from the algae covered bench on the near side of the pool. That bench was the crux of a Supreme Court decision in 1976 that prevented the extinction of the fish. At the time developers were digging deep industrial wells to promote the agricultural development of the adjacent valley, and the water level at Devils Hole began to drop. The court put a stop to the drilling, and the surrounding region became the Ash Meadows National Wildlife Refuge. It turns out to have been an astonishingly lucky turn of events, as the refuge has the largest concentration of endemic species in the continental United States (Hawaii is the only state with more endemic species).
So here is the cropped and enlarged version of the image above, which doesn't show much, but remember I was more than 100 feet away.
It's not every day that one can see the rarest of anything. If you ever find yourself in the Death Valley region, don't pass up the opportunity to see these fascinating creatures. They could be extinct any day despite our incredible efforts.
Wednesday, May 20, 2015
Driving Through the Most Dangerous Plate Boundary in the World: In the Pleistocene, a Different Kind of Danger
|An Egret and Tule Elk at the San Luis National Wildlife Refuge near Los Banos|
|The Cosumnes River Preserve north of Stockton|
As I said in the previous post, the agricultural development isn't necessarily a bad thing. With an increasing population of mouths to feed in the world, it would be silly not to utilize the richest soils on the planet. But we do live in a highly interconnected ecosystem, and we need to preserve what we can of the richness and diversity of life in our world. A few wetlands have been protected from development to allow the survival of some of the migratory birds that overwinter in our valley, like the Sandhill Crane, the Ross's Goose, the Snow Goose, and many others. Some of the rivers flowing through the valley are still allowed to reach the sea, preserving salmon and other aquatic species. There is a great deal of conflict about where to define the limits of water and land use, especially in this horrific drought year.
|The Cosumnes River north of Stockton|
This past year I spent as a new birder has been a revelation as I have sought out those small corners and edges of the valley that preserve something of the original ecological richness. I was stunned to find that flocks of tens of thousands of cranes and geese spend their winters just a few miles from my home near Modesto.
|Snow Geese and Ross's Geese at the Merced National Wildlife Refuge|
|The Tule Elk herd at the San Luis National Wildlife Refuge|
This blog series has mostly been about the "most dangerous plate boundary" in the world, referring to the geologic hazards inherent in living near an active subduction zone: earthquakes, tsunamis, and volcanic eruptions. But a different kind of danger lurked in the Great Valley when humans first arrived: the so-called "megafauna": an ecosystem of large mammals that mostly went extinct just 10,000 or so years ago.
|Wooly Mammoth at the Paige Museum|
The other common fossil is the horse. Most people think horses came to America with the Spaniards in the 1500s, but they actually evolved in North America and spread to other parts of the world before going extinct in their ancestral home around 10,000 years ago. There were also species of deer and pronghorn, and the buffalo roamed the valley as well.
Though any of these creatures could have injured humans in self-defense, it was their predators that would have made life in the valley terrifying. There were huge Sabertooth Cats. There were Jaguars and American Lions (pretty much the same as African Lions).
The California Grizzly Bear was dangerous enough, but even larger bears lived in the valley as well. The Short-faced Bear was a good 50% larger than a Grizzly, and may have been the largest terrestrial mammal predator ever. They were five feet high at the shoulder, and stood 11-12 feet tall if they chose to. Terrifying indeed.
They were smaller than the cats or bears, but the Dire Wolves hunted in packs, and that made them perhaps even more dangerous than the others. They were 25% larger than today's wolves.
The Great Valley would have been a dangerous place for humans when they arrived 13,000 years ago or earlier. It's possible that the megafauna is extinct today because humans had tools for hunting and defense, but the connection is not yet clear. Climate change could have played a role too, or disease, or any other number of possible explanations. In any case, I feel a sense of loss when I wander through the few remaining pieces of original habitat imagining the creatures that used to live here. A sense of loss, but at least I am not so fearful of being maimed or killed.
Are you interested in seeing more of these creatures? If you are ever traveling in the Great Valley for any reason, make the time to stop at the Fossil Discovery Center in the Madera area. The very famous La Brea Tar Pits are the other great source of information on the extinct megafauna. The Paige Museum at the tar pits is an excellent place to visit when you are in Los Angeles.
Tuesday, May 19, 2015
Driving Through the Most Dangerous Plate Boundary in the World: The Sea Floor that Became the Greatest Agricultural Region on Earth
As noted in the last post, the sediments have yielded up a fascinating collection of fossils over the years, including mosasaurs, plesiosaurs, ichthyosaurs, and even the fragmentary remains of a few dinosaurs. The valley was a seaway for the better part of 200 million years.
It is no longer a seaway. In the last few million years, California's tectonic framework underwent huge changes. The subduction zone was extinguished in the central and southern parts (subduction continues in the north state). A new plate boundary emerged: the San Andreas transform fault. Compressional forces along bends in the fault line raised the Coast Ranges, and the seaway of the Great Valley slowly gave way to river deltas, and then alluvial fans. In the last five million years, the Great Valley has been a terrestrial environment, with numerous river channels, gigantic lakes and vast grasslands. Large herds of grazing animals wandered the plains, pursued at times by terrifying predators (look for them in the next post of the series). Countless millions of birds made use of the wetlands during their long seasonal migrations.
The biggest and most far-ranging change in the Great Valley during the last five million years may have been that which took place only in the last 150: agricultural development. Millions of acres of grasslands, lakes and wetlands were drained and plowed. The rivers were dammed and diverted into artificial watercourses that took them hundreds of miles from their natural channels. Thousands of wells were drilled that brought prehistoric groundwater to the surface. Parts of the valley subsided thirty feet or more as the water was withdrawn. A mere 5% of the valley floor retains its natural character. Most of the animals are gone, shot to extinction (the California Grizzly Bear, for instance), or pushed to marginal environments in the Sierra Nevada or the Coast Ranges. The migratory birds are crowded into a few precious wildlife refuges up and down the valley.
Still, living here does have some benefits. Given our journey through the most dangerous plate boundary on the planet, the Great Valley doesn't exactly look geologically menacing. It is relatively far away from the most active earthquake faults of the state, and is even farther away from the most dangerous of the state's volcanoes. We don't get hurricanes, violent thunderstorms or blizzards, and tornadoes are exceedingly rare. The idea of dangers from landslides is laughable (except that I know of at least one fatality in Modesto caused by a slide). But we do have two threats: droughts and flooding.We are in the midst of the worst drought in recorded history, but with the development of an El Nino weather pattern in the Pacific, we could have catastrophic floods in only a few months. We can never really predict what can happen. In 1861-62 the floods were widespread that the state capitol had to be removed to San Francisco for a few months. The valley was a gigantic lake twenty miles wide in places.
|Flooding on the San Joaquin River in 2006.|
The map below shows what could happen if we get a repeat of the 1861-62 floods, an event the meteorologists call an atmospheric river storm (ARKStorm). They also refer to this as the "other big one", because the potential for damage is greater than that of a major earthquake, at least in the Great Valley.
Monday, May 18, 2015
Driving Through the Most Dangerous Plate Boundary in the World: Into the Realm of the Drowning Dinosaurs
|The sediments of the Great Valley Group form the parallel ridges trending diagonally across the photograph.|
We've been making our way on a blog journey through this most dangerous plate boundary. The remains of the subduction zone have been lifted and exposed by erosion in the Coast Ranges. So far we have been observing the rocks of the accretionary wedge, the intensely deformed material that has been churned up within the trench of the subduction zone (see this post for an example). In our last post, we crossed through the oceanic crust of the Coast Range Ophiolite in Del Puerto Canyon in the Diablo Range. At the end of that post we crossed the Tesla-Ortigalita fault and entered into the exposures of the sediments of the Great Valley Group. We are now in the rain shadow of the Coast Ranges, and the slopes are barren of trees.
|This large slump in the lower part of Del Puerto Canyon is the location of the discovery of the first dinosaur fossil ever found in California, in 1937.|
Check it out!
|From Dinosaurs and other Mesozoic Reptiles of California, by Richard Hilton|
Sunday, May 17, 2015
Driving Through the Most Dangerous Plate Boundary in the World: Exploring the Oceanic Crust Without Unobtainium
|But many flowers do exist in Del Puerto, at the right time of year.|
similar to those of the Marin Headlands (above), but pillow basalts are a bit harder to find in Del Puerto Canyon. Other parts of the oceanic crust are well-represented however. Pillow basalts form during eruptions onto the sea floor. The rocks of Del Puerto formed much deeper in the crust. The eruptions of basalt on the sea floor were fed by numerous sheet dikes in the mid-levels of the crust, which were in turn supplied by plutons of basaltic magma that later cooled slowly to form gabbro plutons. Gabbro looks like no other rock in the coast ranges (below).
check out this original post for the series.