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The Face of the Earth
Natural Landscapes, Science, and Culture
By SueEllen Campbell, Alex Hunt, Richard Kerridge, Tom Lynch, Ellen Wohl
UNIVERSITY OF CALIFORNIA PRESSCopyright © 2011 The Regents of the University of California
All rights reserved.
Landscapes of Internal Fire
* ON THE SPOT: OVER A RIVER OF LAVA SueEllen Campbell
We park the cars where lava obliterates the road, then set out across the wavy, corrugated terrain of Kilauea's lower edge. The view is sweeping, simple, and subtle: to our right the clean line of the Pacific, to our left the deceptively gentle slopes of Kilauea and Mauna Loa, the most massive mountain on earth, and underfoot a wondrous textured sheen of iridescent blacks.
Despite the warm, muggy air, everyone in the group of volcanologists who have allowed me to tag along is booted, gloved, blue-jeaned, and hard-hatted, and so am I. Given all the warnings I've read, I feel a bit uneasy, so I'm carefully following the route of my most seasoned guide and watching my step on the lava. Thank goodness we aren't crossing the jagged rubble of 'a'a, so sharp and chaotic that every step might bring an ankle-breaking, skin-splitting fall. This pahoehoe is much more level, its ropy coils most often sprawling like pools of stirred taffy or dropped and tangled skeins of yarn, but even it can be tricky when the skeins tip sideways into sinuous ravines. Now and then someone steps on a thin-skinned bubble and produces the sound of breaking glass, a reminder that these black coils might hide lava still hot enough to burn both boot and foot. A step on an especially fragile bit of crust that just happens to cover an emptied lava tube will mean bruises, scrapes, and broken bones—or immediate death if the tube is still full of molten magma. Stray too close to the shore and we might fall with a big chunk of the rock shelf in a spectacular and likely fatal splash. Right now none of these hazards is visible. But I was also out here last night, and that was a different story. Along with dozens of others, my husband and I cautiously picked our way by flashlight far enough out over the black to see just the outside edge of one spot where a river of orange lava hit the ocean and shattered into black sand and a gaudy burst of steam. We spent a long time watching these fireworks and studying the scattered flickerings on the slopes above, spots where fresh, bright lava was advancing toward the sea, expanding the land itself—reminding us, showing us, how all such oceanic islands have been built.
Somewhere up to our left, we knew, was Pu'u 'O'o, the side vent of Kilauea that has been erupting pretty much continuously since 1983. Everywhere these lava flows have left kipukas, islands within islands of untouched vegetation, shady refuges for many of Hawaii's endemic species. Where we were, on the wet, windward side of the Big Island, lava is covered in mere decades with a tangled scrub of ferns and other hardy plants, though on the dry, leeward side, the lava flows stay bare for a very long time.
Today we are aiming for a hazard: a skylight, a hole through the top of an active lava tube.
Now the leaders of our group are slowing down and gathering in our stragglers. "We're here," one says, points to our right, and leads us in a wide circle until we are facing back toward the cars. We inch forward. The air grows warmer, then hot. Something sharp and acrid hits the back of my throat and I make my breath shallow. My eyes begin to water. Wind rushes across my ears. My heart pounds. I stop moving and look—ahead a few feet, and then down.
How can I describe this?
I see a river of fire, but fire without flames, without those pale yellows, blues, and greens of a campfire, just a stunning intensity of reddish orange that says nothing so urgently as hot. I feel it scorching my skin. Thicker than water or syrup, it's the color of an electric stove burner on high. It pulses as it flows, the pulsing of hot coals, of blood in arteries. It's very fast and mostly silent—a quiet hiss, an occasional soft gurgle. It's maybe ten feet across, no telling how deep. Patches of darkness appear and disappear on the surface, orange cooling to black, folding under, returning to liquid. It looks like the films I've seen of liquid steel flowing out of huge vats into the forms of I beams, the outpouring of some enormous underground foundry.
This is not the familiar stuff of Earth's surface, this beautiful, terrifying river of fire. It is the material of the mantle channeled upward through magma chambers and plumes, melting as the pressure on it lessens closer to the surface. I have learned this. But something closer to instinct tells me what it is, too, something beneath or maybe before words, some recognition hard-wired into my species by our long association with volcanic landscapes. I know that just here and just now I'm seeing the inside of the planet, the world turned inside out.
All Earth's landscapes are shaped in large part by structures and forces that lie below our feet, beyond the reach of our senses, and usually far from our minds. We live on our planet's surface among our human kin, things we ourselves have built, plants and other animals; time moves for us at a rate set by our own heartbeats. We can't see the spinning of the earth's core, the drifting of continents, the rising and falling of mountain ranges, and usually it takes an educated eye even to recognize the traces of such slow and mighty happenings. Sometimes, though, the ground buckles, mountains explode, water boils into the air, and our curiosity and imagination snap awake. We glimpse the inside of our globe, maybe also a different kind of time, and we begin to wonder just what it is that we stand on.
It may be that this is one of the oldest human questions. We developed as a species at least partly in Africa's Rift Valley, where the earth's surface is tearing apart and underground forces are especially visible, and many of our earliest ancestors lived among hot springs, geysers, volcanoes, and boiling lakes of lava. We know this because aridity and volcanic ash are both excellent preservatives that have helped keep for us such evidence as the footsteps of two or perhaps three walkers captured about 3.6 million years ago between two layers of ash in Laetoli, Tanzania. These hominids were probably members of the species Australopithecus afarensis, as was the woman now called Lucy, who lived some four hundred thousand years later in Ethiopia's Afar Depression, an even more active tectonic region farther north along the rift. Like the walkers' footprints, Lucy's bones were first on the surface, then swallowed into the earth's near depths. Brought back up into the light, such traces of our ancestors' moving bodies raise questions about both our planet and our own nature. Their brains were much smaller than ours and their thought processes different (they did not, for instance, know how to make stone tools), but they walked the way we do, upright, all ten toes facing forward, with a spring in their step from their arched feet. It is hard to imagine that they did not feel some of the things we do about the ground we share. At what point in our evolution did we begin to experience not just fear at such sights—mountains turning into giant clouds of ash—but also awe and curiosity about our world? And when did we begin to imagine things we could neither see nor touch?
Not just coincidentally, many of our earliest civilizations appeared in tectonically active areas, where volcanoes created fertile soils and where the uplift caused by colliding plates led to varied habitats and a mixture of fresh and salt water. In Indonesia and Central America, in the Andes and around the Mediterranean, in the sorts of places that most vividly allow us to glimpse and then create stories about the hidden inner nature of Earth, landscape features like volcanoes have been key shapers of human myths, religions, natural philosophies, and sciences.
Geological violence, we have often thought, must come from the actions of powerful beings who live inside or beneath volcanoes—gods, monsters, spirits. If so, we need to propitiate them, offer them sacrifices, or call to our defense other beings who are equally powerful but more benign. There are many such figures. The fire goddess Pele lives in Hawaii's volcanoes, the monster Oni in Japan's. Papua New Guinea's are home to the Kaia spirits. The Titan Typhon is imprisoned under Etna, along with his jailkeeper, the metalsmith Hephaestus (called Vulcan by the Romans), and the one-eyed giants, the Cyclops, who help Hephaestus at his forge. (The Titans were the first Greek gods, later overthrown by the Olympians. Their mother was Gaea, Earth; their father was Ouranos, Sky. Their names show up often in the context of geology.) Those who live near Etna and Vesuvius are protected by the Christian saints Gennaro and Agatha. Satan is ruler of a volcanic hell, and the lion-headed horses described in the Bible's book of Revelation breathe fire, smoke, and brimstone, which is volcanic sulfur.
Stories about characters like these recognize the real mystery and raw power of Earth's interior. They show us the contrast between small humans and mighty natural forces. Lava streaming down a volcano's slopes does look like long strands of hair, as it becomes in images of Pele. When they erupt, volcanoes do rumble, bang, throw out rocks, and shake the land, as stories about angry Oni and Typhon suggest. Fresh lava does resemble the melted metal of forges. And the heat and sulfuric vapors of active tectonic features do torment the human senses. We watch the world, and then we think about it with the same kinds of plots, images, and characters we use to think about ourselves; we apply our understanding of human motives, emotions, and actions to the world around us; we personify. The stories that result are the ones we usually call mythological and religious.
For a long time, some of us have also studied the natural world by looking for laws, processes, essences, and principles—often retaining personification for its metaphorical and rhetorical strengths but trying to set it aside as a source of literal explanations. This is an effort with a complicated history, one that we'll glance at in this chapter as we begin to explore some of the ways we have seen landscapes shaped by forces from inside our planet. We'll focus on the European tradition that is most often called natural philosophy. This tradition, generally speaking, developed (roughly between 600 B.C.E. and 1900 C.E.) into physical sciences like geology, chemistry, physics, and astronomy, the fields that we might say are most concerned with general laws and those that have most to do with landscapes shaped by tectonic forces. (The companion effort, natural history, which typically paid more attention to specific and often anomalous natural details, developed into biology and other life sciences. Only in the past two centuries has the word science taken on its current professional and disciplinary meaning.) We'll also look at current scientific ideas about tectonic landscapes. Along the way, we'll consider such questions as how our understanding of nature involves cultural and subjective forces—imagination, curiosity, wonder, and storytelling—as much as it does careful observations, logical deductions, and classificatory schemes. And, as we'll do throughout this book, we'll keep an eye out for places where cultural and scientific frameworks (these labels, of course, oversimplify for convenience) come together to shape our knowledge of and responses to particular kinds of landscapes.
IMAGINING THE INTERIOR
Let's look at some of the ways this long tradition has found to envision the physical and especially the hidden nature of our planet. What did the natural philosophers observe, think, understand, imagine, propose?
We must begin with the world's basic elements. For many early European theorists, these were fire, air, water, and earth, along with their corresponding qualities of heat, cold, wetness, and dryness. For such a simplification to work, of course, each of these four elements and qualities has to be understood broadly. So fire encompasses all sources of heat and light, including the sun, lightning, stars, and fresh lava. Air includes all gases, not just those we breathe. Water includes other liquids. And earth includes solids of all kinds. Some theorists added to their list of basics a mysterious substance they called ether, something others saw as a purer form of air or of fire. Ether—a word whose root means "to kindle, burn, or shine"—fills the atmosphere beyond the reach of air, past the clouds or the moon, and it might also be a key constituent of the soul. (This has always been the most poetic element, probably because of its intangibility. Consider Alexander Pope's wonderful line, "All the unmeasured aether flames with light.") Other thinkers added a similarly intangible "quintessence" (literally, the fifth essence) to describe the substance of which heavenly bodies are made; for alchemists, the quintessence was a substance latent in all things, one that might, ideally, be abstracted. And many insisted that change is essential as well—a force that affects everything else, the only thing, paradoxically, that endures. Variations on these ingredients and their interactions dominated all kinds of theories from the Greeks and Romans through the Renaissance and even into the nineteenth century, a testament to their flexibility and comprehensiveness as explanatory and organizing categories.
What made earth rise above water into hills and mountains? Do seafloor and dry land regularly change places, or has the process of drying out been continuous since the biblical Flood? What accounts for the sequence of rock layers? What created precious metals and gems, and how are they distributed? Is Earth losing heat, and what caused its heat in the first place? How might such oddities as corals and fossils be explained? And, more specifically, the questions examined in this chapter: What is inside the earth? Why do volcanoes erupt? How does rock melt? What creates earthquakes? Why are hot springs hot, and where is their source of water?
To answer all such questions, earth, air, fire, and water have sufficed in some combination. Consider, for instance, the question of what lies far beneath our feet. The planet is full of air and windy caverns: this is what Lucretius, Aristotle, Seneca, and Pliny thought. Or it is filled with water, great lakes, watery abysses, rivers, and moist vapors, said Plato, Virgil, St. Isidore of Seville, and Paracelsus—a theory that lasted at least nineteen centuries. Descartes declared it to be full of exhalations. John Leslie, in the nineteenth century, imagined it filled with light. And many have envisioned Earth as a globe of incandescent caverns and passageways of fire.
And the very center of the earth, the core? It is fire itself, said Pythagoras (500 B.C.E.), Athanasius Kircher (1665), and Christopher Polhem (1731). Something molten, imagined Empedocles, the philosopher we credit with insisting (about 450 B.C.E.) that everything changes constantly. Perhaps it is an empty space to which the rays of stars penetrated, then began growing toward the surface as metals, proposed Johann Glauber, 1661. Benjamin Franklin thought the core was hot gas, or maybe metal-rich fluid. It must be magnetic material (William Gilbert, 1600; Thomas Cooper, 1813), or heavy metals that sank to the center of an original ball of mud (Amos Eaton, 1818), or something solid that had absorbed heat as the planet passed through a hot region in space (Simon Poisson, 1835). Or maybe it was a great empty cavern (Mary Somerville, 1840); a dense cube or spherical tetrahedron (Richard Owen, 1857); fluid (James Dana, 1879); supercritical gas (Siegmund Guenther, 1884). Many of these theories involve change, too. Cores expand, collapse, or trade places with the crust. Heavy metals sink and precious ores grow outward.
Inside the planet, interactions among the basic elements cause earthquakes and volcanoes. From the time of the early Greeks into the nineteenth century, many natural philosophers attributed these events to the motion of winds through caverns and tunnels, the heating of these winds by friction and sometimes compression, and then their release. Vapors are often involved, they thought, caused by heat (both interior and solar) acting on rain, or by the "fermentation" (that is, chemical reactions) or burning of coal, bitumen, sulfur, and other minerals; sometimes the winds are simply "exhalations." More winds mean more pressure, perhaps explosions, and stronger earthquakes; ventilation shafts might be dug to help release that pressure. Winds that catch fire melt stone into magma and then propel gases, rocks, and ash out of craters and vents. Or explosive quakes and eruptions happen when underground fires encounter underground water. For some, volcanoes are safety valves that help reduce earthquakes. Both are more common near seas and oceans, where wave and storm pressures force salt water into the earth through fissures, and where the phases of the moon and tides affect the timing of tremors. Occasionally, it was thought, some surface event set off these forces: several days of lightning, a passing comet. Or perhaps internal exhalations release electricity, which in turn creates both earthquakes and lightning.
Excerpted from The Face of the Earth by SueEllen Campbell, Alex Hunt, Richard Kerridge, Tom Lynch, Ellen Wohl. Copyright © 2011 The Regents of the University of California. Excerpted by permission of UNIVERSITY OF CALIFORNIA PRESS.
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