May 22, 2005
THE SIERRA NEVADAS, VERSION TWO
Very unusual for this time of year, this has been a chilly, rainy week in the foothills. It hasn't rained much more than it might during the winter, but what rain we had added itself to snow-melt from above, and that caused worries about flooding. On Thursday some of us hiked to the bottom of the canyon just to gawk at the rampaging river. From above we can't see the river, but we'd been hearing its powerful roar and we knew it must be something to see.
In fact, around here it's impossible to ignore the lay of the land and the matter of geology. At some point even the most indifferent person has to wonder "Why is that enormous canyon next to us?" or "Why do so many rock strata in the canyon's wall stand vertically instead of lying horizontally like in most places?" or "Why do the Sierra Nevadas rise so majestically to the east, while the broad Central Valley lies just to the west?" or "Why are there so many earthquakes around here?"
In the 1960s when I was working toward a degree in geology, only about ten minutes of just one of the hundreds of geology lectures I attended dealt with the theory of plate tectonics, or continental drift. At that time most college profs considered the idea that continents could float atop an earthly core of magma as too outrageous to seriously consider.
Now the science of plate tectonics very neatly answers the above questions. Now I can stand next to my trailer and visualize myself as riding atop a massive, 350-mile-long block of granite plowing into the western side of Nevada.
Well, here's a simplified outline of the story:
400 million years ago, long BEFORE the Earth's landmasses crammed together to form the supercontinent of Pangea, a coastline of the land that would someday constitute North America lay where today Nevada and Utah are found. Then the floor of the Pacific Ocean began grinding beneath the North American Plate. Over millions of years, unimaginably intense buckling and fracturing caused rock to melt and molten magma from deep within the Earth to work toward the surface and sometimes erupt as volcanoes.
As a result of all this friction, buckling and fracturing, about 150 million years ago, off the future North American western coastline, a volcanically active "island arc" appeared -- in size and shape probably similar to Japan and Indonesia today, which are considered to be undergoing a similar process. Over enormous periods of time the island arc off North America's coastline slammed into the continent, fusing with it. Then North America's Pacific coastline was maybe 50 miles west of were I am now and mountains were formed, but they eroded down. This story is told in greater detail here.
About 75 million years ago more of the ocean's crust was thrown up against the new coastline and was added to it as well, extending North America's coastline even farther into the Pacific. Mountain ranges with volcanoes formed along the new coast but they also eroded down during the next tens of millions of years.
Finally about 5 million years ago a new period of mountain building began that included the rising of our current Sierra Nevadas to the east, and the Coast Range, which on a clear day I can just see across the Central Valley to the west.
The Pacific Floor continues grinding beneath the North American Plate, so the grinding, fracturing and magma-making has not stopped. A few hundred miles north of here Mt. St. Helen is currently building a lava dome inside its crater. Small earthquakes not making the news except locally are occurring regularly in California where the plates grind together, and no one thinks the earthquakes will soon end.
If you have Microsoft PowerPoint installed on your computer you can download a well illustrated presentation outlining the above story in detail here.
You can learn all about continental drift and geological processes associated with it at the Berkeley University Plate Tectonics Site at www.ucmp.berkeley.edu/geology/tectonics.html, where you can even view an animation showing how the continents have drifted during the last 750 million years!
Speaking of geological grinding and fracturing, this week National Public Radio brought to my attention a new website meant to alert the public to pending earthquakes. It also offers a good overview of earthquakes in the US and provides some historical information on big ones.
To see a US map showing the location of recent quakes, with a surprising hot spot appearing in the New Madrid area of northwestern Tennessee, go to http://earthquake.usgs.gov/recenteqs/
For historical archive information on earthquakes in your own state, go to http://neic.usgs.gov/neis/states/
To see where recent quakes have occurred in California and Nevada, go to http://pasadena.wr.usgs.gov/recenteqs/latest.htm
The main homepage is at http://pasadena.wr.usgs.gov/
We're near El Dorado National Forest and the other day we decided to take a hike there. Fred has a battery-powered, belt-tracked "wheelchair" and you'd be surprised what rough terrain he can negotiate. We walked two or three miles, and Fred managed it so that the battery didn't go flat until exactly upon our return to the van.
Down in the moist, deeply shaded valleys Douglas-firs grew to gigantic sizes. We were a few hundred feet higher in elevation there so Sugar Pines mingled with Ponderosas. Sometimes we caught glimpses of the snowfields on the slopes between us and Lake Tahoe and I had to wonder if all that snow ever would melt enough for me to get up there with a backpack and a tent.
Probably the most memorable discovery we made was of a handsome little orchid growing alongside the logging road we walked on. It was the Spotted Coral-root, CORALLORHIZA MACULATA. A cluster of about 10 white, purple-spotted flowers rose about a foot high, the individual blossoms being about ¼-inch long. You can see my very nice close-up of a flower (thanks to Fred & Diana's wonderful digital camera) at www.backyardnature.net/sierras/wildflow.htm#Coral
Like the Broom-rape I told you about last week, Coral-root possesses no chlorophyll, has no green parts, and therefore doesn't photosynthesize its own food. Also like Broom-rape, coral-root's stem grows belowground producing no real leaves. However, unlike Broom-rape, which is a parasite, coral-root is a saprophyte. Its roots have a complex relationship with a certain mycorhizal fungus, so the fungus and coral-root work together to break down or convert organic matter to the nutrients they each need.
You can see, then, that coral-roots can only live in a certain kind of place -- where humidity and temperature are high enough and stable enough to be agreeable to the fungus, and the soil's organic matter is of the proper kind and amount. The moist, protected, deep valley beneath tall conifers where we visited that day seemed to fit the bill.
We're at about 2600 feet here and the forest is dominated by Ponderosa Pines. Between here and the mailbox the road I jog on each morning dips into a valley where Digger Pines begin appearing. Digger Pines dominate the lower, drier elevations. By the same token, on our coral-root hike we were a couple hundred feet higher in elevation and in rainier territory, and there Sugar pines were about as numerous as Ponderosas. Here we say we're "going down into the Digger Pines," and "going up into the Sugar Pines." Let me tell you about those Sugar Pines.
Sugar Pines, PINUS LAMBERTIANA, are famous for being the tallest American pine (up to 200 feet) and for producing the longest cones of any American conifer (up to 26 inches long). During our hike I photographed the tree and a couple of long cones being held by Diana, and you can see the pictures at www.backyardnature.net/sierras/trees.htm#Sugar
Sugar Pines are members of "the White Pine group," and therefore on the stems the needles cluster in bundles of five. The authors of "Sierra Nevada Natural History," Tracy Storer and Robert Usinger, say very prettily of the Sugar Pine, "A big mature Sugar Pine on a mountain crest, with long cones hanging at the ends of its spreading branches, conveys the feeling of a beneficent patron." Well, here I'm slope-bound with no mountain crests at hand, but I can just imagine what they're talking about, and someday when it warms I'm hiking upslope until I see such a patron-pine.
Of course I'm always comparing our pines here with the Loblollies back in Mississippi. Both Ponderosas and Sugars produce trunks that to my Southeastern-biased mind seem much too large for the amount of green branches the trees bear. It would seem those Loblollies, having so much heat and rich soil, would produce the largest trunks. I suspect that what's happening is that the trees here grow much slower. They have larger trunks, but they take longer to produce trunks of a given size than fast-growing Loblollies.
The "sugar" part of Sugar Pine's name derives from the fact that fire and physical wounds cause a kind of resin to seep out that hardens into white nodules. If you're hard up for chewing gum, this can be chewed, and it is actually slightly sweet.
Only someone who has gardened or walked around much in fire-ant territory can know how thankful I am that here we have no fire ants. In fact, the most bothersome ant here is just a stinker who drops from trees, gets tangled in one's hair, and that's hardly a bother at all.
At first this ant's penetrating odor doesn't strike you as particularly bad, but it's one of those oily, musky smells that with time becomes nauseating. Usually you only smell them when they drop from a tree and you brush them away, then sniff your fingertips. However, this last week I've spent a lot of time identifying them as they streamed up and down a California Black Oak next to my trailer, where they have a nest in a rotted-out injury, so I can tell you this: Their odor is so intense that if you hold your face six inches above a marching column you can become thoroughly disgusted with the smell.
Happily, California ant-enthusiasts have a well-illustrated, easy-to-use, online key to the comon California ants at www.ipm.ucdavis.edu/TOOLS/ANTKEY/. Even if you're not in California, if you have access to a powerful magnifying glass and an ant, I think you might enjoy using the key because it obliges you to pay attention to features you surely never even imagined existed.
California's ant fauna comprises 270 species (245 native, 25 introduced). About 25% of the native species are endemic to the state or to the "California Floristic Province," which includes northern Baja California in Mexico and southern Oregon.
You might enjoy browsing AntWeb's different ant collections -- there's a special section on "world ants" and one on "California Ants" -- where you click on a thumbnail and see much larger pictures and information at www.antweb.org.
The "Ants of California" page is at www.antweb.org/california.jsp.
Here are the four main ferns along my jogging trail:
The first three are just ferny ferns looking and behaving normally. The Gold Fern, however, shows some extra pizzazz. First, it specializes in rocky ledges and crevices. More than that, however, when you flip its frond over usually the bottom surface is heavily dusted with brightly gold to white powder. The powder isn't spores -- it's just produced by the frond's undersurface and I can't explain why. It does look nice, however. You can see my recent pictures of both the Gold Fern and the Male Fern at www.backyardnature.net/sierras/ferns.htm.
FIVE MILLIONS YEARS AGO
Above I made the point that the current Sierra Nevadas rose only about five million years ago. When the block of land atop which I'm writing to you from rammed into Nevada, an earlier Sierra Nevada mountain range formed, but that one eroded down long before the range I see today appeared. And long before those earlier Sierra Nevadas, today's continents had been joined into a supercontinent called Pangea. But, before Pangea, there had been yet other continents, vestiges of which are to be seen as geological relicts in today's continents.
To help you get oriented among all these millions and billions of years, you might enjoy looking at my annotated Geological Time Scale at www.backyardnature.net/g/geo-time.htm.
To be honest, these histories of mountain ranges coming and going and continents fracturing and welding back together are almost like fairy tales to me, However, I believe them, have studied the evidences, and havin seen with my own eyes many of the proofs of the stories.
The problem is, we humans can't identify with long periods of time. Who really can visualize five million of anything, much less years?
I remember being a little boy in Kentucky repeatedly starting and stopping a team of horses pulling a wagon through a cornfield while my father and grandfather picked ears of corn by hand and tossed them into the wagon. I can remember the thought processes, the assumptions about life, the mind-set that backcountry people had about life then, about being a human being embedded in a nature seething with mud, hot summers and cold winters, mosquitoes, droughts and floods... and I can tell you it was like being another kind of human, maybe another species. And that was me less than 60 years ago.
My opinion is that especially nowadays we need to reflect more on the matter of our lives in the context of the time that Life on Earth is manifesting itself. It's especially important now because never before in the history of Life on Earth has a single species affected the welfare of all other species as now the human species does.
Moreover, never before has the human species been so influenced by a single monoculture philosophy of living, as it is now by the philosophy of ecosystem-destroying, self-indulgent consumerism.
Today our leaders, instead of disciplined conservation and a more elegantly efficient use of energy, are encouraging nuclear power, and drilling for oil in ecologically sensitive places.
The half life of plutonium is about 24,000 years. When you think how human society has changed just during the last fifty years, and remember that most energy in our culture is wasted unnecessarily, how can it possibly be right to produce more plutonium, which is the most deadly agent known for Life on Earth?
Our leaders say they'll store nuclear waste in Yucca Mountain and put up signs that can be understood by humans when our languages have morphed into other languages, or people have stopped reading altogether. But, who knows what kind of social craziness we are capable of during the next 24,000 years? There must be at least a million religion-crazed fundamentalists right now eager to bring an end to "this sinful Earth" and set themselves snugly in Heaven. Moreover, even after 24,000 years we'll still have half the plutonium we started with.
Life on Earth began at least 3.85 billion years ago, but any life-form or way of living destroyed in half a second of right-wing or left-wing economics or any hue of religious fervor will be extinguished for eternity.
When I look at the five-million-year-old Sierra Nevadas, this is a question they seem to be asking me: What kind of morality or religiosity is it that takes such great, needless chances with life it has taken the Creator 3.85 billion years to create?
Best wishes to all Newsletter subscribers,