Terriers, Trilobites and Plate Tectonics

An 1888 New York Times article about groundhogs and shale deposits reminds me that the geology of this part of the U.S. has quite a bit in common with parts of the United Kingdom.

To be sure, a great number of things on the surface are different, but if you scratch below the surface of the soil, you will find "It's a small world after all."

I am not the first person to notice.

As early as the 1860s, scientists in Wales noted that the trilobite known as Paradoxides davidis, occurred in both Wales and the Northeastern seaboard of the U.S. near Newfoundland.

The odd thing -- the "paradox" that gave the Paradoxides genus its name -- was that this shallow water trilobite was separated from its identical brethren by a thousand miles of deep ocean. How could that have occurred?

Paradoxides trilobites were not the only thing that occurred in fossil beds separated by thousands of miles with no connective geological tissue to be found between. How could this have happened?

Around 1915, Alfred Wegener of the University of Marburg in Germany, suggested a bizarre explanation for which he was roundly ridiculed: that the continents drifted around like icebergs on the ocean, with the the lighter granite and dirt of the surface continents slipping and sliding on the harder and denser basalt that lay below.

Wegener was a little vague as to what forces were propelling the continents -- he suggested centrifugal force, or perhaps a lunar pull similar to that which raises the tides. One thing he was certain of, however, was that continents did move about.

In the 1950s, the U.S. began to systematically map the ocean floors incidental to planning for submarine warfare. The systematic mapping of the world's oceans revealed two phenomenon unknown up until that time; the presence of a world-wide system of mid-ocean ridges, and the presence of deep trenches along the edges of what appeared to be geological "plates."

In 1962, U.S. geologist Harry Hammond Hess postulated that sea floors were spread by magma pumped out of mid-ocean ridges, and that a counter-vailing trend was going on in the deep ocean trenches where the earth was being pulled back into the core through a process of subduction.

In essence, Hess said, mid-ocean ridges produced new material, while the deep trenches consumed old material.

According to Hess, the earth was essentially on a long slow boil fired by atomic energy being released at the core of the planet, with the continents more-or-less-floating like congealed scum on top of a soup of magma.

With Hamond's explanation and Wegner's theory, the table was set for Dr. J. Tuzo Wilson of the University of Toronto to postulate the unifying theory of Plate Tectonics to explain why parts of the U.K. and North America shared identical fossil beds.

Wilson suggested that the United Kingdom and America had collided into each other some 500 million years ago as the Iapetus Ocean, a precursor to the modern Atlantic, closed up. As a result of that collision, the Appalachian Mountains were pushed up, along with the mountain ranges of Wales and Scotland. Because these mountain ranges are made up, at least in part, by the folded remains of the same strata, they share some of the same characteristics and fossils.

Between 200 and 60 million year ago, however, the continents drifted apart again thanks to the addition of new material from the mid-Atlantic ridge.

The new split between the lands masses was not perfect, however, and as a result parts of Wales remain attached to Newfoundland, and parts of America remain attached to Scotland.

So what does this mean for terrier work?

Perhaps not much, but it does suggest things are not so different from one side of "the pond" to the other. That said, while I have moved a lot of crumbled slate and shale while digging on the terriers, I have yet to find a trilobite. Apparently, they are a rare find in the U.K. as well.

What is not rare in my area are groundhog holes with slate and shale-littered spoil piles like the one pictured below. Imagine dozens of these in your farm field, each of them with tunnels beneath, and heavy harvesting equipment driven above. No wonder farmers want groundhogs gone; it's can be a matter of safety as well as commerce.

When folks from England, Wales, Scotland and Ireland came to the U.S., they found a country not all that different from their own, at least geologically. Not for nothing does is "Highland County" Virginia called Highland County!
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And, as one recent immigrant huntsman to Virginia told The Fauquier Times Democrat, the piedmont area of Virginia is very similar to Shropshire in the English Midlands on the Welsh border. I'll bet he does not know how true that really is!



What looks like wood chips is actually shale in various states of degradation.
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This Land Is My Land

Today is "World Soil Day," (yes, there is such a thing), which strikes me as as good time as any to talk about the land I dig on.

Where to start?  

Let me start by noting that one of writer John McPhee's best little gems is a long essay called "The Gravel Page" which was first published in The New Yorker, and later reprinted in the McPhee essay collection entitled Irons in the Fire.

"The Gravel Page" is about forensic geology, which sounds like an absurd topic until you realize there are people so studied in the shifting sands, alluvial deposits, and quartz formations of the world, that they can look at the dirt under your car's fender and tell you where in the world it came from.

And they can get it right within a mile or two. Amazing.

The Gravel Page is more than excellent writing -- it is also good story (always that!) mixed with an exploding cosmos of knowledg,  and a new way of looking at the world. This is non-fiction writing at its best.

I bring up John McPhee because I recently got two different emails about soil structure. One was about New Jersey soil as sandy and easy to move as cake mix, the other about Vermont ground so riddled with rock it requires three people, a pickax, and a steel digging bar to consider working a terrier to ground.

Ah, America!

In truth, we are a large and varied country and though we are one land, we are many soils. In fact, as odd as it sounds, about 20 state legislatures have actually named their state soils.

Indiana's state soil is called "Miami" (no doubt named after the Indian tribe), while New Jersey's is called "Downer," and is described as "a grayish sandy loam."

Vermont's state soil is thin stuff called "Tunbridge" which is described as being "20 to 40 inches deep over schist, gneiss, phyllite, or granite bedrock."

Virginia's state soil is something called "Pamunkey." No one I know of has ever heard of Pamunkey, but it is described as the type of wash-down found along the banks of the James River and "which originated in every physiographic province in the Commonwealth, and therefore represents the WHOLE state better than other soils."

Ah, a political soil invented by a committee and named after a native tribe. Of course.

Maryland's state soil is something called "Sassafras" which is described as "a Benchmark and Hall of Fame soil series." Really? There's a Hall of Fame for soil?

In truth, the Maryland dirt in which I dig defies all categorization. You may have good friable soil in a field, but 50 yards away will be a belt of trees and an area packed with cobbles and hard marl. A small ridge above the field may be of igneous rock so hard it could be used as an Easter Island hammer stone. Everywhere -- seemingly without rhyme or reason -- you will find broken pieces of shale mixed together like playing cards dropped by God Himself. What kind of soil have you got? We've got it all!

I know about the soil in my neck of the woods from digging on it. This is not book knowledge. That said, I was rather pleased last night when I came across a web site with maps of Maryland soil by County, and with enough detail that I could identify the location of individual farms where I have been digging on the dogs. I cannot read much out of the maps yet, but I will drill a bit and see if I can sort it out. These maps, after all, are the back story of this land.

The geology of this region is not a simple one. I live and dig near the area where Maryland, Virginia and West Virginia come together. A fall line shoots through the middle of it, and the ocean is not far away.

To the West lie the Appalachian Mountains, one of the oldest mountain ranges in the world, worn down to a few thousand feet from peaks that may have once been as high as the Sierra Nevadas.

To the East is the sandier soil of the coastal flats and the Delmarva Peninsula.

The Piedmont -- the geology of the area I think of as my home -- is the area that lies in between. These are the ancient foothills of the Appalachian mountains. Here most of the old rock has degraded to good soil, but there are still regular ridges of very hard stuff that Mother Nature and Father Time, working together, could not reduce to rubble.

The area I call the Piedmont Breaks is the area running roughly parallel to Route 95, and is normally called the "Fall Line". This is the very edge of the Piedmont -- a kind of geological no-man's zone between the true Piedmont and the Coastal Plain.

Here the continental plates of Europe and Africa have ground up against North America. As the continents crashed into each other, ancient rock folded up and ancient sea beds were pushed far inland. The last really major geological event in this area was the break up of Pangaea during the Mesozoic era, as Africa pulled away from North America, forming large basins and shallow seas (the so-called Iapetus Ocean) that teamed with wildlife. The bits and pieces of broken shale I find all across this area are the vestigial remains of those vast mud-filled basins and ocean shelves.

My own house, quarried from local gneiss and roofed by Vermont Slate, sits almost on top of the Fall Line that is the boundary line between the Piedmont and the Coastal plain.

The house itself sits on a rocky knoll about an eighth of a mile back from the Potomac River. There has been no significant geological activity in this area for many thousands of years. Ground pressure is receding not building. I am not worried about my property values being decimated by an earthquake. About terrorism I am a little less certain -- the Pentagon is only a mile and a half away.

The path down to the river is a gentle slope most of way, but that path ends at a sheer 90-foot rock cliff that goes down to the river. The only way to descend this cliff is to pick your way down steps hewn into the cliff next to a small waterfall. It can be treacherous going in winter.

If you turn left at the base of the cliff, you can walk up the river bank to Chain Bridge about a quarter mile up. If you are traveling in a small boat, you can go no farther that this due to rocks, rapids and falls. Above Chain Bridge is Little Falls, and above that is Great Falls, a stretch of water sufficiently treacherous that it takes the lives of half a dozen people a year -- mostly young fools and foreigners who ignore the warning signs posted in a half dozen languages at water's edge.

I am told this is the steepest and most spectacular fall line rapids of any river in the eastern U.S. The falls were once located at Chain Bridge but over many millennia they have chewed their way upriver to where they are now, in Mathers Gorge.

If you turn right at the bottom of the cliff below my house, you will reach Key Bridge about a quarter of a mile away. This is the bridge that crosses the Potomac River into Georgetown, and it is the way I normally get into the city.

If you were to put a boat into the water just below my house, turn downstream, and paddle 13 miles or so, you would slide pass Mount Vernon -- George Washington's old home. Keep on going and you will reach the Chesapeake Bay. Keep going from there, and you can reach the Caribbean, Paris, London, South Africa, Malaysia, New Zealand, California, and South America. To be on a river with unobstructed passage to the sea is to be connected to quite a lot.

A river at your door is a great thing. Rivers last because they totally renew themselves every 24 hours or so.

The soil lasts because it remains locked up in a vault of its own making.

I am pretty sure that not much else lasts.

We make our headstones out of rock in an attempt to find a kind of store-bought immortality, but after 100 years the names and dates are as meaningful -- and as meaningless -- as hieroglyphs.

Not much else lasts either. I dig on land that has been farmed for over 300 years, and on much of it parts of the Civil War were hard fought.

Yet there are no bones to be found, no bullets, no buttons, no bottles. Dinosaurs and deer have lived and died on this land for eons, and yet they have left not a single mark behind. Trees and bushes have risen (and fallen) for thousands of millennia but they too have left no sign of their existence except (perhaps) the soil itself.

In a thousand years, I have little doubt that almost nothing extent today will be intact and recognizeable. But the river will still run through Mathers Gorge, and the soil maps made in 1950 will still be good.

"By the sweat of your brow you will eat your food
until you return to the ground, since from it you were taken;
for dust you are, and to dust you will return."
. . . - Genesis 3:19

Great Falls on the Potomac.  This is a repost from May, 2007

Round and Round in the Circle Game

May the circle be unbroken.

I found this graphic on my computer today while I was looking for something else. I suspect I saved it a few years back when I was writing about global wildlife migrations and the fact that everything is connected, left to right, up and down, all over the world.

Yes, migration is about more than birds. It includes whales, sharks, tuna, seals, wildebeests, elephants, turtles, pronghorn antelope, butterflies, dragonflies, and even senior citizens going to Florida for the winter.

Of course, the circle game is bigger than that isn't it?

The nuclear molten core of the earth is a bubbling cauldron of magma, and that magma is seething up and cooling down, like boiling water in a pot.

Even as the molten rock goes up and down, it slowly pushes the vast plates of the earth around, and on top of these massive plates of super dense rock floats "the light stuff" like granite, dirt, sand, redwoods, elephants, and us.

And, of course the great nuclear ball that is the sun heats up the oceans which have massive upwellings of water at the equator, and massive downwelling at the poles.

These in turn drive vast ripping ocean currents we call the Gulf Stream or Humboldt's Current, or the Indian Ocean Gyre, and these in turn determine where the fish feed and whether we need to throw another log on the fire in December.

Several times a day the gravity of the moon pulls billions of pounds of water this way or that, driving water backward up rivers, fueling tidal bores, and pushing waves up and down a million miles of crab-speckled beaches.

The atmosphere too boils up and cools down, with massive upwellings and downwellings of air, and vast ripping currents of wind driving themselves around the earth in clear patterns we call the Air Stream or the Trade Winds or the Doldrums, depending on where they are and what they are doing.

The ground we live on also boils with life as worms and groundhogs, ants, plants and fungi, turn over the soil and build upon it, pulling things down and lifting things up.



And on top of this boiling planet we fight the change.

We try to build for permanence and prevent extinctions.

We fear both global warming and global cooling.

We worry about energy and where we will get it.

We are upset when butterfly, bird, mammal and fish migrations change, and we are equally upset when they do not, and the animals pass away in the face of changing circumstances.

As a rule we are oblivious.

Elephants now live in the heat of Africa and Asia, but their cousins once roamed the frozen north, and we do not think to wonder why none are there now.

Birds fly overhead unseen, coming from places we do not wonder about, and going to places we cannot imagine.

We do not know the name of the drainage we live in, or how the creek behind our house makes its way to the ocean.

We do not even know the names of all the trees in our backyard.

Meanwhile, we go to work in our prisons on the road, stuck in traffic, insulated from the weather, our minds spinning; the world's longest playing record, all the grooves running to the great self-obsessed hole in the center.

“Efé children of the Ituri Forest in Zaire (Rep. of Congo, central Africa) begin the Osani game by sitting in a circle, feet touching, all connected. Each child in turn names a round object like the sun (oi), the moon (tiba), a star (bibi) an eye (ue) and then goes on to name a figurative expression of “round” like the circle of the family, togetherness, a baby in the womb, or the cycle of the moon. As players fail to come up with a term that is “circular” they are eliminated from the game. Eventually, only one remains. Tradition has it that this player will live a long and prosperous life.” :: source

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