Out here in Western Oregon, where the North American continent grinds up over the floor of the Pacific ocean, three of our planet's most irrepressible forces have combined to produce one of its most irresistible places. In the summertime, when the sky is blue and the cool air takes on that peculiar, surreal clarity that artists once sought in Santa Fe and Taos, tourists stream in over the passes and up the interstate from California. At the height of the season there are so many visitors that you can't hike the ancient forests without the ever-present risk of rounding a bend and suddenly confronting a member of your own species. The beaches become downright congested. At times you may see a dozen or more people, and perhaps even a dog or two, crowded into a single mile of sea-lapped sand.  

Of the three irrepressible forces that built this landscape, two are part of the attraction -- continental drift and volcanism. The mysteriously beautiful Coast Range, a low chain of mountains that rises directly from the sea, is all that's left of an ancient volcanic island chain that the continent overran some fifteen million years ago. The knife edge of the advancing plate literally scraped the islands off the ocean floor and pasted them onto the land. A hundred miles farther inland, the Cascade volcanoes are also a product of continental drift and volcanism, but by a different mechanism. They are a part of the famous Pacific ring of fire, and as such they mark the zone where the sea bed, overridden and forced down into the earth by the weight of the continent, melts into the mantle. The lighter components of the melting rock rise as magma to fuel the volcanoes that parallel the coast from Canada to Northern California.  

As always, the dynamics of the earth tie directly into the lives of the people who live on it. To the human eye volcanoes are among the most beautiful of landforms; these particular volcanoes, which vary from smoking cones and lake-filled craters to extinct ice-carved fingers that reach silently for the sky, are among the most beautiful on earth. So as surely as subducted sea floors melt to produce magma, and as surely as magma rises to the surface to produce volcanoes, so volcanoes produce . . . tourists.  

The influx of visitors, which in recent decades has become as predictable as the change of seasons and as immutable as the drift of continents, creates an uneasy balance of temperament and necessity. Oregonians, by and large, are a solitary breed. Most of them are recent immigrants, and they did not come to this far place to rub shoulders with outlanders loaded down with cameras. At the same time, the Oregon economy is not always as green as its forests, and the tourist dollars are sorely needed.  

I have heard a rumor that, somewhere, scientists are working furiously to develop methods of better refining the raw material of tourism, seeking some formula by which they can produce the tourist dollar without its noxious side effect -- which is to say, the tourist. But until a breakthrough occurs, state officials urge us to be tolerant of the invaders and appreciative of the cash they spend. Sometimes this counsel is effective and sometimes it isn't. Several decades ago, in a paroxysm of insularity, a popular governor publicly asked tourists to "Visit Oregon . . . but please don't stay." Even today we see an occasional "Californicators go home" bumper sticker.  

Still, most of us abide the tourists, often by simply ceding the season to them. We either shrink back into our own secret places in the more obscure parks and forests or just stay at home. In my case the latter isn't a bad alternative, since home is 50 acres of fir in the eastern watershed of the Coast Range. There are always fences to mend, roofs to fix, and gardens to tend . . . and the tourists, in any event, are a passing malady. Come Autumn they will vanish.  

What will send them packing is the appearance of the third great force that shapes our green landscape -- a force which, for reasons not fully understood, possesses a unique ability to turn human knees rubbery and send grown men fleeing south.  

This is somewhat difficult to explain, for our species is not generally a cowardly one. In fact, we are frequently brave to the point of foolhardiness. We drive at high speeds without our seat belts, consume a steady diet of starch and fat, hang glide, climb rock faces, bungi jump from bridges, leap out of airplanes . . . and then brag about it. People love to stand at the leading edge of the continent and watch the sea crash against the black rocks, and never mind that each year several of their brethren are plucked off those rocks and carried away by a slap of this same great sea. They are even drawn, like lemmings, to active volcanoes. When Mount St. Helens began its latest eruptive cycle, the combined forces of the belching earth, the National Guard and the U.S. Forest Service proved insufficient to keep the curious at bay. Yet, come autumn, the first few drops of cool rain end the summertime party and turn the tourist army into a fleeing rabble that jams the southbound lanes of the interstate.  

This third great force of nature, which is to say rain, owes its power to the high Cascades. The mountains, rising into the sky, form a great climatic barrier between Western Oregon and the rest of the United States. On the one side, there is continental weather; on the other, Pacific monsoon.  

Generally speaking, continental weather is determined in a tug-of-war between air masses from the Arctic and the balmy southern latitudes. Winter weather in places like Detroit and Baltimore originates in the frigid high pressure systems that spawn in the far North and move southward. In the spring, when the sun begins to cast shadows north of the Arctic circle, the strength of those highs begins to diminish; this opens the way for warm, wet cyclones to come spinning up from the tropics, producing the April rains that are so famously responsible for the May flowers. But these storms, or what's left of them by the time they get to Oregon, lap ineffectually against the eastern slopes of the Cascades.  

Coastward of the mountains, springtime is triggered by the northern movement of the jet stream, which allows a stationary Pacific high pressure system to build off the coast. Out to sea the winds shift, and begin to blow from north to south. This, through a complex coupling of air and sea, causes the upwelling of cool water near the shore. The result, for Western Oregon, is steady dry winds blowing in off the sea - precisely the kind of cool, fair weather that Californians and inlanders dream about. The summer, then, belongs to the tourists.  

But at summer's end, when the sun moves south, the jet stream follows it - and so does the warm Pacific High. As the winds offshore change, the cool ocean upwellings come to an end. Now the offshore air flow is out of the south, which drives warm water north into the Gulf of Alaska. This anomalous warm spot on the fringes of the Arctic is the source of intense atmospheric energy, breeding an endless series of low pressure storm systems. One after another these cyclones come roaring south, hook east somewhere off the Olympic Peninsula, and come ashore in such rapid succession that one storm front yields only to make way for the beginning of the next.  

As these waves of warm, wet air hit the first continental rise they are already condensing into rain and fog. When they climb into the Coast Range they cool further, releasing torrents of rain. The rain decreases somewhat on the lee side of the range as the air flows out across the Willamette Valley. But then the steeper and higher rise of the Cascades unleashes more torrents. High on the west-facing slopes of the mountains the rain changes to snow, which builds up yard upon yard. This is the great moisture bank which, come spring, will melt to recharge the streams, rivers and waterfalls that will so intrigue a new crop of tourists.  

By the time the once-saturated air crosses the last Cascade ridge it has been wrung dry. The demarcation between the green world of Western Oregon and the much larger expanse of arid mountains and chaparral that lies beyond the Cascades is dramatic and defining. Suddenly, sometimes in only a few yards, the water-loving fir gives way to sparser stands of ponderosa. A short drive to the east, the ponderosa becomes thin and stunted and then, in turn, surrenders to Western juniper and sagebrush. Beyond lies the northernmost reaches of the Great American Desert - the classic American West, cowboy country to this day, a sparsely populated land of leathery-skinned people whose generations were defined, in corpus, soul and psyche, by the cruel extremes of a climate in which the searing white summer sun seems mainly suited to bleach the bones of the winter kill.  

Thus there is, in truth, no Oregon: There are two Oregons, split personalities that share the same legal and political persona with considerable discomfort. If the reigning cultures here had evolved over the millennia in the same slow fashion that they developed in the old world, the watershed of the Cascades would undoubtedly be a border - bristling, probably, with gun emplacements and guarded checkpoints. As it happened, however, the political boundaries of the West were drawn by faraway politicians, most of whom would never see the countryside or show the slightest interest in its natural divisions. They met in drawing rooms, cut their deals, and drew their lines on maps, and that's the way it is to this very day. In this respect, if in no other, the Western states have much in common with the cantankerous countries of the Middle East, halfway around the globe.  

Like their cowboy forbears, Oregonians who live on the high desert are a weathered and independent lot. Each election they send a cantankerous minority delegation over the mountains to the state legislature in Salem. There they serve, by contrast, to define the character of the solid majority of Oregonians -- a white-faced people who live in the rain. The valley people may themselves be as much a product of environmental extremes as their neighbors from across the mountains, but the nature of those extremes could not be more opposite. Burning heat and killing cold are rare, here in Western Oregon, but the stories you may hear about the endless months of shadowless gloom are most definitely true.