Mountains of the Heart: A Natural History of the Appalachians
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Stretching almost unbroken from Alabama to Belle Isle, Newfoundland, the Appalachians are one of the oldest mountain ranges in the world. In Mountains of the Heart, renowned author and avid naturalist Scott Weidensaul shows how geology, ecology, climate, evolution, and 500 million years of history have shaped one of the continent's greatest landscapes into an ecosystem of unmatched beauty. This edition celebrates the book's 20th anniversary of publication and includes a new foreword from the author.
ISBN-13: 9781938486883
Media Type: Paperback(20th Anniversary Edition)
Publisher: Chicago Review Press Incorporated
Publication Date: 02-16-2016
Pages: 336
Product Dimensions: 5.90(w) x 8.90(h) x 1.00(d)
Scott Weidensaul is an author and naturalist who has written more than two dozen books on natural history, including Pulitzer Prize finalist Living on the Wind: Across the Hemisphere with Migratory Birds, The Ghost with Trembling Wings, Of a Feather: A Brief History of American Birding, and The First Frontier: The Forgotten History of Struggle, Savagery and Endurance in Early America. He lectures widely on wildlife and environmental topics, and is an active field researcher, specializing in birds of prey and hummingbirds. He lives in Schuylkill Haven, Pennsylvania.
The Supple Rock I flicked a big, glossy black carpenter ant off my leg, shifted slightly against the pine tree at my back and thought about rocks. The view from the lip of the Linville Gorge invites deep thinking. The Linville River, which spills out of western North Carolina's Blue Ridge, has cut a drastic slice into the earth here, a drop of more than a thousand feet to the sliver of water way down below, crowded by canyon walls wrapped in pine, oak and hemlock. It was a warm, dry, hazy day, and the woods smelled heavily of pine — an intoxicant after a long winter. The nose misses odors during the cold months but doesn't realize it until spring uncorks the perfume. Rocks are fundamental to the Appalachians, but unless you are a geologist or a weekend rock hound, you're unlikely to spend much time thinking about them. For most of us rocks are just part of the scenery — something to climb, or stub our toes on, or skip across a quiet lake. And when the nonexpert tries to concentrate on rocks, as I was doing, they often mock the effort. Of all the earthbound sciences, geology may be the most humbling. No other discipline save astronomy asks us to step so far outside of ourselves, to think in such desperately inhuman lengths of time or on so confoundingly huge a scale. The Linville River has a fairly short shot at glory. It flows down through the gorge for about eighteen miles, then emerges into the gentle Piedmont hills, where it is immediately swallowed by the waters of Lake James, the westernmost impoundment on the Catawba River system. But it makes the most of its brief freedom. Depending on how you measure such things, Linville Gorge is the deepest canyon east of the Mississippi, in places measuring more than seventeen hundred feet from riverbed to mountaintop. One would expect such a vertical cut to reveal the ordered layers of rock, much as the Grand Canyon's painted sediments trace billions of years of geologic history. But in the Appalachians geology is a squirrely science, never giving you exactly what you expect. Take the Linville Gorge, for instance. At the head of the chasm, the river crashes down over a spectacular series of waterfalls, tier after tier of foam that booms in the enclosed valley. The rock over which it flows is metamorphic; that is to say, incalculable heat and pressure deep inside the Earth's mantle (where this rock once lay) converted the original granite into a new form, known as gneiss. This transformation took place about a billion years ago. The water pours through a narrow slot in the high gneiss walls, makes a turn and fans out in a final cascade to a deep pool. The rock underlying the pool — and the waterfall — is actually younger by 500 million years than the gneiss above it. In a well-ordered world where geology was easy, this sort of thing wouldn't happen. But tracing the geologic history of the Appalachians is, as some geologists have pointed out, like reconstructing a hit-and-run car wreck by examining the dents and the crumpled metal, peering at the twisted shards and looking for scrapes of paint from the other car. The southern Appalachians are a particularly nasty dent, and the culprit was the bulge of Africa, which rear-ended North America about 290 million years ago. The impact shoved much of the continental rim inland, piling it up in untidy heaps. Thus, older rock was pushed on top of younger rock, which — at Linville Falls and elsewhere — is sometimes exposed by erosion. This incoherence of rock has driven geologists to distraction. On a map the Appalachians form a cohesive whole, strung out almost seamlessly over two thousand miles, but different regions of the chain have radically different ancestries. The age of the rock differs wildly; some of it is sedimentary, some igneous (like granite, made up of once-molten magma) and some metamorphic. The rock is far older than the mountains, just as the rock from which a stone house has been constructed is far older than the building. Nor were all the ranges of the Appalachians uplifted by the same forces or at the same time. Hardy pines cling to the sandstone cliffs at Cheaha Mountain, Alabama, near the southern terminus of the Appalachians. Geologists have long known that the Appalachians arose in distinct pulses spread over hundreds of millions of years, but the mechanism that pushed them skyward was unclear. Books written before about 1965 speak vaguely about accumulated heat and pressure, and about the tendency of lighter crustal zones to buoy up. "Many mountains and plateaus are high because they are light," says one volume from the 1940s on the northern Appalachians, leaving the subject at that. The less said, apparently, the better. That changed by 1968, when the theory of global plate tectonics came to prominence. At its simplest, tectonics theory suggests that the Earth's outer crust, or lithosphere, is made up of enormous, distinct plates (seven to ten major slabs, depending on who is counting, and a bunch of smaller platelets), which float on denser layers of molten and semi-molten rock. As these plates move, they heave and buckle, hitting each other to raise mountain ranges and tearing apart to form oceans. Heavier oceanic plates, made up of dense basaltic rock, tend to slide beneath the somewhat lighter continental plates of granite when the two meet. The process, known as subduction, is happening now along the Pacific Northwest coast, where the dense Juan de Fuca Plate is subducting beneath the granitic North American Plate, forming inland volcanoes like Mount St. Helens. The idea that the continents were once joined together and have since moved to their current positions has been around for a long time — much of it as material for jokes. In the nineteenth century, the theory was ignored in favor of "the doctrine of permanence," which held that continents and oceans might change shape slightly as the Earth contracted, but would not move in any meaningful degree. When first proposed scientifically in 1912 by German meteorologist Alfred Wegener, the idea of drifting continents was ridiculed, even though Wegener supported it with data indicating that South America's eastern bulge and Africa's western bight hold similar rock formations and fossils. And, of course, the continental shapes of that bulge and bight fit together like pieces of a puzzle. Unfortunately, Wegener could not supply a convincing mechanism for all this continental shuffling, and his theory won few converts. It took nearly fifty years for the idea of continental drift to reemerge, this time largely due to exploration of the sea floor. Enormous, mid-ocean rifts had been discovered, with the spreading out to either side at a rate of two inches a year as magma welled up and solidified, while the edges were being sucked beneath other plates. It was found that as molten rock cools, particles within it line up with the Earth's magnetic field, allowing geologists to determine where the rock was formed; the particles also record the periodic flip-flop of the Earth's poles, permitting aging of the rock. The results were astounding — the continents had indeed ambled and pirouetted all over the globe. Wegener had been right, and subsequent measurements around the world have given us a fairly good idea of how the continents were arranged in times past. One of the hardest things for a nongeologist to remember is that here wasn't always here. As I look over Linville Gorge — at the swallowtails drifting through the rangy crowns of the hemlocks and tiny spring azure butterflies that look like swatches of summer sky — everything looks so permanent. But these drifting islands of crust have wandered quite a distance. This little piece of the Appalachians, for instance, was once pivoted ninety degrees on its side and floating somewhere well below the equator. Same rock, different location. Combined with an enormity of time, the whole subject of geologic history becomes as slippery as an eel. Nor have the continents always held their current shapes. As they drift, continental plates gather up the others' leavings, scraping up loose chunks and islands known as terranes in a process called accretion. Think of a hand sliding across a snowy windshield, piling up slush along its leading edge, and you get the general idea. Much of coastal New England and eastern Newfoundland, for instance, is apparently an accreted terrane, the remnants of a microcontinent which geologists named Avalonia. The land never stays still for long; the continents dance across the mantle, bumping and grinding gracelessly, forming partnerships and dissolving them on a whim. The long, complex history of the Appalachians is rooted in this vast waltz. In the briefest of nutshells, the Appalachians as we know them today were formed over a period of about 500 million years, in three separate mountain-building episodes, or orogenies. The first, the Taconic Orogeny, peaked about 440 million years ago and pushed up a chain of mountains that subsequently eroded to nothing, providing the material for the next wave of peaks. Then came the Acadian Orogeny, about 375 million years ago during the Devonian Period, the Age of Fish when the first amphibians were just deciding they liked dry land. These first two orogenies were largely responsible for what is now the northern Appalachians, while the third and most recent, the Alleghenian Orogeny, gave shape to the central and southern Appalachians about 290 million years ago. If you take the history of the Earth as a calendar, with January 1 marking its formation, then the beginning of this sequence — the start of the Cambrian Period — doesn't come until the middle of November. The Taconic and Acadian Orogenies occur around the beginning of December, and the Alleghenian Orogeny happens on about December 10. Those who construct these geologic calendars always like to point out, with insufferable smugness, that we human party-crashers didn't arrive until a few moments before midnight on New Year's Eve. The Taconic Orogeny came at a time when the continents looked much different than they do today. Africa, South America, Antarctica, Australia and parts of Asia were welded together in a supercontinent known as Gondwana. North America, Greenland, Ireland and Scotland comprised a land mass named Laurentia, which was tipped on its side from the modern position and separated from Gondwana by the Iapetus Ocean. (The names may seem confusing, but there is a method to the madness. For example, in Greek mythology Iapetus was the father of Atlas, just as the Iapetus Ocean was the forerunner of the Atlantic.) Finally, there was northern Europe, an island continent dubbed Baltica, which sat to the east of Laurentia. Starting around 500 million years ago, Iapetus began to close, drawing Baltica toward Laurentia. The Baltica Plate slid beneath the Laurentian Plate, generating tremendous heat and sending lava plumes up through the coastal rock, causing the kind of volcanic mountains seen today along the Pacific Rim. There is no mountain so tall that erosion cannot knock it down. By the end of the Silurian Period, about 400 million years ago, the mountains of the Taconic Orogeny were worn to gravel, which was deposited by rivers in a huge delta to the west that stretched from West Virginia to New York. These sediments eventually became the hard, erosion-resistant quartz sandstone and conglomerates that now cap many Appalachian ridges, and are exposed as the ghostly gray boulder fields of Pennsylvania's Kittatinny Ridge or the vertical knife-edge of Seneca Rocks in West Virginia. The continents continued their slow-motion collisions. Laurentia and Baltica crunched together to form a new land mass known to geologists as the Old Red Sandstone Continent, in honor of a distinctively rusty rock strata. Where the two parts of this supercontinent met, a new range of mountains called the Caledonides rose, in an episode called the Arcadian Orogeny. The Caledonide Mountains included what are now the northern Appalachians, but the range continued on the "European" side of the suture, forming mountains that marched across what would become Britain and Scandinavia as well as eastern Greenland. The Caledonides in what is now New Hampshire or Maine did not look like the modern-day White Mountains or Traveler Range. They were young and snaggletoothed then, like today's Alps. What we now see are the eroded stubs of once great peaks. Later, when the Atlantic began to split open, the plates drifted apart, carrying the sibling hills thousands of miles from each other, but the haunted glens of Scotland's Highlands are close kin to the northern Appalachians. Little wonder that the Scots and Scots-Irish, forced to the New World by the brutal clearances of the eighteenth and early nineteenth centuries, found something familiar in Nova Scotia and North Carolina. In the interlude between the Acadian Orogeny and the final mountain-building period a hundred million years later, tremendous changes took place. The land had become cloaked in forests — not of oak and hemlock, but of primitive seed-ferns, giant horsetails and tree club-mosses. Insects and other arthropods were abundant, and amphibians had aggressively colonized the land. With the Old Red Sandstone landmass sitting near the equator and shallow seas lapping both rims of the Acadian mountains, conditions were perfect for the growth of lush swamps. The eventual result, of course, was coal — the product of millions of years' worth of fallen vegetation turned to peat in the oxygen-poor water, buried beneath later sediments, then compressed and heated into the varying states of coal. These ranged from crumbly lignite, or brown coal, through bituminous (soft coal), to the much altered, cleaner-burning anthracite, or hard coal. It's not surprising that this period of geologic history is known as the Carboniferous. In the Appalachians, bituminous deposits are common in a wide swath from Alabama to western Pennsylvania and parts of the Atlantic Provinces in Canada. Anthracite, on the other hand, is restricted to a few narrow pockets in the Pennsylvania and Virginia ridges. I grew up in Pennsylvania's anthracite belt, a region scarred by the deep mines, with their outwash of stream-killing acid water, and huge strippings that gape empty-mouthed beside spoil banks. The anthracite industry boomed in the nineteenth century but went into a precipitous crash in the early twentieth as other, more convenient fuels like oil dominated the market. More and more of the great breakers, which sorted coal from worthless shale and graded the chunks by size, squatted outside the towns, abandoned, the huge banks of windows pocked with smashed panes, the spindly conveyor belts that spread out like the legs of insects rusted in neglect. The shale banks were unstable, dangerous places for kids, but I spent more hours than I could count combing their slopes for fossils. The coal swamps left their mark in the soot-gray sediments that the mining companies discarded, and few fossils from any time in history can match the elegance of those from the Carboniferous Period. I still know of no feeling quite so charged as splitting a slab of shale open along its weakest bedding plane and exposing the secrets inside. The seed-ferns in particular are exquisite, the imprints of their fronds smooth and glossy against the flat, fine-grained shale; the ancient leaves are sometimes still touched with a film of white or orange. Many formerly enormous plants of the coal age have survived by becoming smaller. I remember the shock of recognition one day when I found a wonderfully preserved horsetail stem at the base of a shale bank, just feet from a feathery stand of living horsetails known as scouring rush. The modern species are scarcely two feet tall, but the Carboniferous versions were mammoth, reaching sixty feet or more into the air. For more than 200 million years, the continents had been drawing closer and closer together, fusing in larger and larger clots. Now, as the Carboniferous Period came toward its end, only two huge landmasses remained, the Old Red Sandstone Continent poised in the north and Gondwana in the south — and they, too, were approaching each other, squeezing the Iapetus Ocean out of existence between them. Their collision caused the last of the three Appalachian orogenies, named the Alleghenian by geologists. Western Africa smacked into the southern rim of the Old Red Sandstone Continent, forcing up the southern Appalachians. The impact, which stretched over a 50-million-year period, was epic in its force, reflected still in the tortured strata of the central and southern Appalachians and the plateaus of their western slopes. Across Pennsylvania the resulting ridges make a serpentine curve — the "fingerprint," in a sense, of Africa's bulge. Rock layers that had been deposited horizontally were folded, cracked and twisted, and much of the eastern rim of the continent was shoved as far as 160 miles to the west, over younger formations. Another 200 million years of erosion has, in some places, cut through weak points in the older rock, forming "windows" to the younger rock entombed beneath. Like Linville Falls, the famous valley of Cades Cove in Great Smoky Mountains National Park is a window. Interstate highway road cuts are good places to see the results of the Alleghenian Orogeny's prodigious energy. In Pennsylvania, the builders of I-81 removed a piece of Spring Mountain, exposing the swirled layers of Carboniferous sandstone inside. Down the middle of each wall, however, is a diagonal slice–the Spring Mountain Thrust Fault, along which the rocks had been pushed some fifty feet from their original position. The Spring Mountain fault is a blip, however, compared with the Pine Mountain Overthrust on the Cumberland Plateau of Tennessee and Kentucky, a feature so big it can be seen from space. Here, as the giant piece of continental rim slid west, its southern flank hung up on a pocket of more stubborn rock; the force sheared off along the Jacksboro Fault, forming two distinct right-angle bends in the mountain. Satellite pictures show it clearly, but you can see its shadow on highway maps. With your finger, follow I-75 northwest from Knoxville. At Lake City, the overriding rock hit its snag at Walden Ridge, and the highway from here to Buckeye traces the fault line. Then the mountain, and the highway that follows it, make a precise ninety-degree turn to the right, back along the edge of the old crustal plate. Read an Excerpt
Mountains of the Heart
A Natural History of the Appalachians
By Scott Weidensaul Fulcrum Publishing
Copyright © 2016 Scott Weidensaul
All rights reserved.
ISBN: 978-1-938486-89-0
CHAPTER 1
(Continues...)
Excerpted from Mountains of the Heart by Scott Weidensaul. Copyright © 2016 Scott Weidensaul. Excerpted by permission of Fulcrum Publishing.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
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Table of Contents
Contents
Prologue: Cheaha Mountain, Alabama,
1. The Supple Rock,
2. Islands in the Sky, Travelers on the Wind,
3. The Wooded Sea,
4. From Fertile Waters,
5. Keeping Faith with the North,
6. Thunder, Dimly Heard,
7. Roots in the Hills,
8. Pinus and Castanea,
9. Winter in the High Lands,
10. Seeing a Forest for the Trees,
11. Ultima Thule,
Epilogue: Mount Abraham, Vermont,