The Earth in Motion

excerts of

Chapter 1
Geology of Prince William Sound


"Nothing endures but change." Heraclitus

The high afternoon sun beats down warming the small, rounded rocks of the Nellie Juan moraine lulling me into a state of dull and drowsy reverie. The reflected warmth, unlike for this latitude, suddenly retreats before a chilled zephyr issuing down from the deep-blue face of nearby Nellie Juan Glacier. I start from my afternoon's reverie, suddenly awakened to a renewed awareness of the spectacle that surrounds me. Before me, the iceberg-strewn lagoon gives way to precipitous, gray-granite cliffs wedged apart by the aquamarine, tumbling form of Nellie Juan Glacier. Occasionally, a thunderous rumbling fills the air as mammoth chunks of ice crash from the 200 ft. face into the waters below.

Immediately to the left of the glacier's front lies a stark landscape of gray granite rubble backed by sharp sedimentary peaks rising above a gray granite base. Here, the glacier's rapid retreat has been so recent that soil adequate for plant growth as not yet had an opportunity to form. Farther back to my left, the jagged lunar landscape slowly gives way to a more verdant, rounded scene where mosses and lichens slowly transform the mineral-rich rock into a thin layer of topsoil which will soon support the roots of willow, alder, and eventually spruce and hemlock forests. This is a hobbit land of lush, tarn-dotted meadows stretching their green forms over a rolling landscape of glacially scoured granite.

To my right, in the next valley, towering granitic domes dominate the shores of Deep Water Bay - a miniature marine Yosemite. Behind me, stretch the sparkling blue waters of Prince William Sound whose rugged mountains, deeply indented shorelines and forested islands contain innumerable scenes of equal beauty making this one of Earth's truly unique places.

The thought strikes me, as it often does, that I am privileged to be here at this exact point in time and space. Yet, it was not always like this - Prince William Sound. As the sun-warmed sediments filter through the fingers of my outstretched hand, I reflect that even the minerals composing this sand probably originated 200 million years ago somewhere off the ancient equator. How many times had they been molded into solid rock only to be weathered or ground once again into fine sediments before reaching this snapshot in space and time? The thought strikes me that Prince William Sound like the Earth and Universe itself has been a place of constant change and has endured endless cycles of restless creation and destruction.

Geologically, the forces of creation arise primarily from the Earth's internally produced heat resulting from radioactive decay deep in its crust and molten core. Internal heat provides the motive force that drives the restless crustal plates over the face of the globe. Where plates tear apart in mid-ocean, the crust weakens allowing molten rock to flow forth on the surface, creating new ocean floor. Colliding plates buckle the earth's crust thrusting up great mountain ranges. The forces of collision melt the deeply buried rock which bursts forth in volcanic violence, spewing out new continental crust or slowly simmers below the surface eventually cooling into great, granitic plutons.

The forces of geologic destruction reside mostly in heat produced externally by the sun. The external heat engine causes the earth's atmosphere to circulate bringing the droughts and dust storms, rains and floods, blizzards and glaciers that erode mountains and send sediments to settle in the deep ocean basins. For billions of years the twin forces of creation and destruction have been embraced in a Shivalike dance whose every movement transforms the face of the Earth. Continents have been born, wandered the face of the Earth and died. Whole oceans have come and gone. Great mountain ranges have thrust skyward only to be relentlessly leveled by the slowly driving forces of erosion.

Evidence for the coming to be and passing away of the Earth's crust abounds from huge, awe-inspiring volcanoes to insignificant sediments washed by raindrops to the sea. But these changes require time - periods of time so vast that even the imagination reels before them. How can a being whose very lifespan is but a mere flicker in the black abyss of geologic time begin to comprehend the meaning of a million years? A million years . . . If we represent this expanse of time by a 12" ruler, the span measuring a human generation would not even be visible to the naked eye. If we represent a million years by a yardstick, then a single life-span would appear as a fine, barely discernible mark. To perceive a single life-time in the expanse of time it took to form the rocks of Prince William Sound would require a measuring stick nearly 90 feet long!

Our story begins 200 million years ago - a period of time so vast as to be almost incomprehensible. Yet, as the age of the earth goes, we are speaking of rather recent events. If we imagine Earth's 4.5 billion years collapsed into the span of a hundred years, then we are considering only the last four and a half years. (Chapter 1. pp. 1-3).