The Kaibab-Coconino Plateau

As the Paleozoic Era gave way to the Mesozoic, some 225 million years ago (MYA), an ovoid upwarping of Earth's crust developed in what is now northern Arizona.  Reinforced during the Laramide Orogeny (the formation of the Rockies, 70 MYA), this broad ridge was eventually covered by layers of Mesozoic and Tertiary sediments (both erosional and volcanic).  Late in the Tertiary Period, the Miocene-Pliocene Uplift (stretching from about 15-5 MYA) lifted the entire Colorado Plateau and its rim of mountain ranges another 5000 feet, increasing stream erosion across the Province.  Rising on the west side of the Continental Divide, the Colorado River flowed westward and gradually southward to enter the Sea of Cortez; en route, it crossed northern Arizona, entrenched in the younger sediments that covered the Kaibab-Coconino ridge.  As the Colorado Plateau rose beneath it, the river was forced to cut down through this ridge of Paleozoic rock (and the upper layer of the ancient Precambrian basement that lies beneath it).  Augmented by the wet climate of the Pleistocene (2 to 0.01 MYA), the Colorado thereby sculpted the Grand Canyon, the most spectacular chasm on our planet.

The ridge itself, oriented NNW to SSE, has since been uncovered by erosion.  Streams from its eastern edge drain directly into the Colorado (or into the Little Colorado south of the Grand Canyon), while its northwest flank drains to the Colorado via Kaibab Creek and its southwest flank feeds the Cataract River, another tributary of the Colorado.  The exposed ridge is composed primarily of Kaibab limestone overlying Coconino sandstone; that portion north of the Grand Canyon is known as the Kaibab Plateau while its segment south of the Canyon is referred to as the Coconino Plateau.  The rock strata of the plateau, deposited during the Permian Period, form the upper layers of the Grand Canyon

The Kaibab Plateau rises to elevations that exceed 9200 feet, supporting a rich forest of fir, spruce and aspen, giving way to ponderosa pine and then pinon-juniper woodlands at lower elevations.  The Coconino Plateau is 7400 feet above sea level at the south rim of the Grand Canyon and gradually lowers toward the west, south and east; it is covered primarily by ponderosa pine parklands.  South of the Coconino Plateau, the landscape is dominated by the high peaks and scattered cones of the San Francisco Volcanic Field, including Humphreys Peak (12,633 feet), the highest point in Arizona.

Colorado's Black Canyon

Near the end of the Mesozoic Era, as the Cretaceous Sea retreated to the southeast, Colorado was a relatively flat landscape of wetlands, sandhills and primitive forest.  Then, about 70 million years ago (MYA), pressure within the North American craton crumpled up the Rocky Mountains, pushing ancient Precambrian rock up through the overlying Paleozoic and Mesozoic sediments.

As soon as they formed, the forces of erosion began to act on these new mountains, filling the intervening valleys with debris.  About 35 MYA, volcanism developed in central and southwestern Colorado, lifting the West Elk and San Juan Mountains; the copious ash, pumice and lava from these eruptions also coated the valleys and basins of that region.  By 10 MYA, the Gunnison River had formed; rising on the west side of the Continental Divide, in the Sawatch Range, and receiving large tributaries from the West Elk Mountains, to its north, and the San Juans, to its south, this river flowed west to join the Colorado.  Entrenched within the erosional and volcanic debris that had settled across the broad, intervening basin, the Gunnison was forced to cut into a ridge of Precambrian gneiss and schist, east of present day Montrose, that was buried within the sediments.  Since that time, the river has sculpted the Black Canyon of the Gunnison from that ancient rock, a process that was augmented during the cooler, wetter climate of the Pleistocene.

Almost 50 miles in length, the Black Canyon is up to 2720 feet deep and 1100 feet across at its rim; at river level, it is much narrower, only 40 feet wide in one area.  The Painted Wall, on the north flank of Black Canyon, is named for the light-colored lava rock that laces its surface and is the tallest cliff in Colorado, dropping 2250 feet.  Within the canyon, the Gunnison River drops 43 feet per mile, a grade that is almost six times steeper than the Colorado River's course within the Grand Canyon.  Named for its shaded walls, hidden from the sun by its deep and narrow topography, the Black Canyon of the Gunnison is protected within a National Park that stretches along its middle (and most spectacular) 14 miles.  Farther west, the Gunnison is thought to have carved Unaweep Canyon through the Uncompahgre Plateau, later diverted northward by a landslide to join the Colorado west of Grand Junction (see my blog on 12-27-10).

The Nature of Volcanism

Volcanoes develop in areas where the heat from Earth's mantle melts the overlying crust.  This occurs along subduction zones, where one of the tectonic plates is dipping toward the mantle, in rift zones, where the crust is thinning (allowing the mantle to move upward) and at hotspots, where a mantle plume is rising into the crust.

Subduction volcanoes are the most widespread form of volcanism on Earth and are concentrated along the Pacific Rim where the Pacific Plate and its associated oceanic plates are dipping beneath the South American, North American, Eurasian and Australian Plates.  The Andes, the volcanoes of western Central America and Mexico, the Cascades, the Aleutians and the volcanoes along the western edge of the Pacific (Japan, Taiwan, Philippines, New Zealand) result from this process.  Other subduction volcanoes include those along the western and southern edge of Indonesia, the volcanic islands of the eastern Caribbean and Mt. Etna, on Sicily, one of the most active volcanoes on our planet.

Rift volcanoes include those above mid-oceanic ridges and those developing along rift valleys in continental crust.  Most oceanic ridge volcanoes are well below the surface of the sea and thus not readily observed; the major exception is the island nation of Iceland, which formed (and continues to form) above the mid-Atlantic ridge.  Continental rift volcanoes are seen along and within the East African Rift and the Rio Grande Rift of the American Southwest; they are also scattered throughout the Great Basin of the U.S. where the crust is being stretched (and thinned).  Hotspot volcanism occurs across the globe, along the ocean floor and beneath/within continental crust; the Hawaiian Islands, the Galapagos Islands, the Canary Islands, Yellowstone, the San Francisco Peaks of northern Arizona and the volcanic field of northeastern New Mexico are but a few examples.

Avalonia

There are few terranes that illustrate the science of plate tectonics and continental drift better than Avalonia.  This micro-continent formed as a volcanic island arc along a subduction zone off the African Coast; at that time, late in the Precambrian Era, Africa was attached to the other southern continents to form Gondwana, which stretched across the South Pole.  During the Cambrian Period, some 530 million years ago (MYA), as shelled marine life was exploding in diversity, Avalonia rifted from the African Plate and drifted northward ahead of the Rheic Ocean, which opened between it and Gondwana.

Late in the Ordovician Period, some 450 MYA, Avalonia docked with Baltica, the craton that now underlies Scandinavia, Eastern Europe and western Russia.  This combined continental mass then collided with Laurentia (proto-North America) during the Silurian Period (440 MYA) as plants and animals were first colonizing the land; the collision forced up the Northern Appalachians, an event known as the Acadian Orogeny.  When the Earth's land masses merged into Pangea during the Permian Period, about 270 MYA, Avalonia was caught in the middle, compressed between the northern and southern continents.

As the Tethys Sea opened east to west, some 200 MYA,  Avalonia remained with Laurasia (the combined northern continents).  During the Jurassic (150 MYA), the Atlantic Ocean began to open, splitting Avalonia as it divided the North American and Eurasian Plates.  Today, fragments of Avalonia form coastal New England, Nova Scotia and the Avalon Peninsula of Newfoundland on the North American Continent; across the Atlantic, it is represented by Wales, England and the northern portion of Western Europe.  Small fragments of Avalonia have also been identified in South Carolina and along the western rim of the Iberian Peninsula.

Australia's Great Basin

The Lake Eyre Basin of east-central Australia is a vast topographic bowl within which streams drain toward the lowest part of the basin, never reaching the sea.  Covering 440,000 square miles from southwestern Queensland to South Australia and from the southeastern corner of the Northern Territory to the northwestern edge of New South Wales, most of it is dry, desert landscape through which ephemeral streams lead to Lake Eyre, in the southwest corner of the Basin.  Nearly dry and coated with salt flats most of the time, the lake fills only twice each Century (on average); composed of a large northern basin connected to a smaller southern basin by the Goyder Channel, Lake Eyre covers 3700 square miles and has an average depth of less than 10 feet (when full)  The lowest point of the lake basin, in Belt Bay of the northern portion, is 50 feet below sea level while the rim of the lake is 30 feet below the level of the sea.

The Lake Eyre Basin began to form about 200 million years ago, when Australia was part of Gondwanaland.  Tectonic forces caused the crust of this region to subside and, within another 100 million years, an arm of the sea invaded the basin; when uplift occurred along the northern and eastern margins of the basin, the sea drained away and rivers flowed across the region, depositing sediments on their way to the ocean.  During the middle of the Pleistocene, about 1 million years ago, uplift along the southern rim closed off the basin and all streams fed Lake Diers, the much larger predecessor of Lake Eyre (as Lake Bonneville preceded the Great Salt Lake in the U.S.).  As the climate became warmer and drier late in the Pleistocene and into the Holocene, the flow through the rivers diminished and eventually became sporadic.  Today, what little water reaches the lake is via three primary river systems: the Georgina River from the north, the Diamantia River from the northeast and Cooper Creek from the east.  Most streams from the west and northwest dry up before reaching Lake Eyre.

During those rare periods when monsoon rains or tropical storms fill Lake Eyre, this remote oasis attracts huge flocks of shorebirds, terns and Australian Pelicans that nest on the islands and feed in the shallows; how these birds know that the distant lake is full remains a mystery.  Lake Eyre National Park stretches along the east shore of the northern lake, just a short 435 mile drive north from Adelaide.  Major towns within the Lake Eyre Basin include Alice Springs, Mt. Isa, Longreach and Broken Hill.

Glacial Lake Souris

Near the end of the Pleistocene, 10-15,000 years ago, large meltwater lakes formed along the retreating edge of the Continental Ice Sheet. One of these, Lake Souris, extended from north-central North Dakota into Manitoba, intermittently connecting with Glacial Lake Agassiz, to its east.

All of these lakes expanded and contracted depending upon their interconnections, the regional climate and the rate of meltwater production. Dammed by tongues of ice or moraines of glacial debris, some would occasionally break through their retaining wall, sending a torrent of water across the flat landscape of the Northern Plains. One such event involved Glacial Lake Regina of southern Saskatchewan, which flooded southeastward into Lake Souris; the broad, shallow channels of this flood remain evident today and are partly occupied by the Upper Souris River and its major tributary, the Des Lacs River.

East of Minot, the Souris River now enters the former lake bed of Glacial Lake Souris, following it north and gradually eastward to merge with the Assiniboine River of southern Manitoba; Lake Souris, itself, eventually drained into Lake Agassiz, which contracted into Lake Winnepeg after drainage opened to the north. National Wildlife Refuges now line the Des Lacs and Souris Rivers which, as we saw last summer, may still flood across the Pleistocene channels and lake beds when a deep winter snowpack is followed by heavy spring rains.

The Flathead River

The Flathead River of northwest Montana rises via three primary forks. The North Fork heads in the mountains of southeast British Columbia and then flows south along the western edge of Glacier National Park. The Middle Fork rises in the Rocky Mountains, northwest of Great Falls, winding northwest and then westward to join the North Fork. The South Fork also rises in the Rockies, more directly west of Great Falls, and flows NNW, where it enters Hungry Horse Reservoir before merging with the combined North and Middle Forks. The primary channel of the Flathead River then enters the Rocky Mountain Trench, a broad valley formed by downwarping of the crust as mountains rose to its east and later occupied by Pleistocene glaciers. Flowing southwestward and then southward, the river passes Kalispell, Montana, and enters Flathead Lake; the Stillwater, Whitefish and Swan Rivers also feed the lake.

The largest natural freshwater lake (by area) in the western Lower 48, Flathead Lake initially formed from glacial meltwater behind a terminal moraine that was deposited late in the Pleistocene; the lake valley was also inundated by Glacial Lake Missoula as it expanded and retreated 30-15,000 years ago (see my blog on 4-2-12). Exiting the southwest corner of its lake, the Flathead River snakes southward across a landscape of plateaus and ridges before flowing westward through a rugged canyon to join the Clark Fork River.

The upper forks of the Flathead have all been designated National Wild & Scenic Rivers and are among the most remote and least disturbed streams in our country. Nevertheless, the North Fork faced possible contamination from proposed coal mining and gas production in southeastern British Columbia over the past few decades; fortunately, an agreement between the U.S. and Canada has, for now, blocked that "development."

Mt. Washington, NH

When I climbed Mt. Washington with a group of friends, in 1974, it was my first experience with mountain hiking. Standing atop the treeless summit, raked by a cold wind and looking out over the surrounding landscape of peaks and valleys, I enjoyed both a sense of accomplishment and the reward of magnificent vistas. We had ascended from Pinkham Notch, east of Mt. Washington, camping below Tuckerman Ravine for the night before a boulder-climbing assault on the summit the following day.

Anchoring the Presidential Range of northern New Hampshire's White Mountains, Mt. Washington tops out at 6288 feet, the highest summit in the northeastern U.S. The Presidential Range, trending southwest to northeast, catches both Canadian storm fronts and nor'easters from the Atlantic Seaboard, bringing copious precipitation to this high wall of Precambrian rock; Mt. Washington receives over 100 inches of precipitation each year, most of which arrives as snowfall (usually exceeding 300 inches). North and northeastward from Mt. Washington are, in sequence, Mt. Clay, Mt. Jefferson, Mt. Adams and Mt. Madison while, to its southwest, are Mounts Monroe, Franklin, Eisenhower, Pierce and Jackson. While the terrain climbs gradually across the western flank of the Range, Pleistocene glaciers carved steep cliffs and ravines along its eastern side; the Grand Gulf curves northeastward from Mt. Washington, Huntington Ravine drops across its eastern flank and Tuckerman Ravine forms a steep wall on its southeast edge.

The alpine summit and its Weather Observatory, which still holds the world record for a human-recorded surface wind speed of 231 mph in 1934 (eclipsed by an automated measurement of 253 mph from Cyclone Olivia, in Australia, 1996) can also be reached via a cog railway or via an auto road that winds up from Pinkham Notch. Whether visitors hike or ride to the summit, they are treated to spectacular mountain scenery and have a chance to observe a wide variety of Northwoods wildlife, including black bears, moose, white-tailed deer and a host of north country birds.

High Deserts

To most of us, deserts are landscapes of dryness, sparse vegetation and perpetual heat. But, in high deserts, the interplay of elevation and dry air produces wide temperature variations from day to night and from one season to another. Examples within the U.S. include the Great Basin Desert, with floor elevations from 5000 to 6000 feet, the Red Desert of southern Wyoming, ranging from 6000 to 8500 feet, and the San Luis Valley of Colorado, with an average elevation of 7600 feet. In all of these deserts, hemmed in by mountain ranges, the annual total precipitation is below 10 inches and surface temperatures may vary by as much as 70-80 degrees F between night and day.

However, the high deserts of the U.S. pale in comparison to the extreme conditions found in other regions of our globe. The Gobi Desert of Mongolia and the varied Patagonian Desert of Argentina are somewhat comparable with regard to elevation but are far larger and are affected by the extreme conditions of neighboring ecosystems. The Atacama Desert of Peru and Chile, the driest on Earth, stretches from the sea to the foot of the Andes and thus harbors varied life zones from zero to 11,000 feet or more. Among the highest deserts in the Western Hemisphere are the Bolivian Salt Flats (12,000 feet) and the Salinas Grandes of Argentina, 12,500 feet above sea level.

But the most impressive high deserts on our planet are the Tibetan Plateau, north of the Himalayas, averaging 14,500 feet in elevation, and the Antarctic Plateau of east-central Antarctica, with a mean elevation of 9800 feet. Despite the fact that its ice and snow harbor over 70% of the fresh water on Earth, Antarctica is our driest Continent, with most of its precipitation falling along the coastal shelves; ascending toward the great plateau, the dry polar air cools further, dropping its meager cargo of moisture on lower terrain.

Siberian North America

Contrary to a popular assumption, the major tectonic plates of Planet Earth do not correspond directly to the contour of the continents and oceans for which they are named. The North American Plate, for example, extends westward from the mid-Atlantic Ridge, thereby including the western half of Iceland, the western half of the Atlantic Ocean, Greenland, Canada, the Continental U.S., Cuba, the Bahamas, the Gulf of Mexico, the northern Caribbean and the country of Mexico. Its western edge generally follows the west coast of Mexico, the U.S. and Canada (excluding the Baja and Southern California, which are on the Pacific Plate), curving westward below Alaska and its Aleutian Chain and then dipping southward to take in the northern islands of Japan; from there, the western edge of the North American Plate angles NNW, cutting across eastern Siberia.

The Chersky Range of eastern Siberia, trending NW to SE, is a swath of parallel ridges and deep gorges; geologically, these mountains represent a compression zone between the North American and Eurasian Plates and are thus prone to frequent earthquakes. Extending northwestward from the Chersky Range is the Laptev Sea Rift, cutting through the Laptev Shelf on the northern coast of Siberia; this rift is a continental extension of the Gakkel Ridge, the spreading zone of the Arctic Ocean which, across the globe, is continuous with the Mid-Atlantic Ridge. The North American and Eurasian Plates are thus diverging along the Mid-Atlantic/Gakkel Ridge and colliding at the Chersky Range.

Of more significance to politically-minded, nationalistic humans, eastern Siberia, including the Kamchatka Peninsula, is on the North American Plate while Southern California and Hawaii are on the Pacific Plate, tied tectonically to Tahiti, the Soloman Islands and Southern New Zealand. Perhaps, if we paid more attention to the geology of our planet and less to our cultural differences, we might be more devoted to our common welfare.

Dry Rivers on the High Plains

Most of the rivers that cross the High Plains of the American West would hardly be recognized as creeks farther to the east. While the primary rivers that rise in the mountains, including the Missouri, Yellowstone, Platte and Arkansas Rivers deserve their title, many of the smaller rivers, heading on the High Plains Province itself, are dry for much of the year, transmitting water only after episodes of torrential rain or rapid snowmelt. Among these sandy channels are the upper tributaries of the Niobrara, Republican and Smokey Hill watersheds.

Cut off from Pacific moisture by the Continental Divide and located far from the Gulf of Mexico, the High Plains only receive copious precipitation when powerful storms draw in moisture laden air from the east, events that most often occur from February through June; indeed, this geophysical province receives less than 20 inches of precipitation each year. Yet, if we study the High Plains topography, we find that these meager conduits have managed to carve ridges, hills and valleys from the otherwise level plain, suggesting that they were more substantial streams in the past. In fact, during the Pleistocene Epoch (2 million to 10 thousand years ago) the regional climate was much cooler and wetter, giving rise to rivers that, in today's climate, have withered to channels of sand, prairie grass and scattered stands of cottonwood trees.

As with other ecosystems across our globe, it is impossible to understand the current geography without an appreciation for natural history and the region's underlying geology. In the case of the American High Plains, Pleistocene rivers sculpted the Tertiary deposits and underlying Cretaceous Sea sediments into the landscape that we find today; feeble and intermittent streams now occupy the valleys that those rivers left behind.

Italy, Earthquakes & Human Nature

After enduring two tragic earthquakes within a span of nine days, residents of northeastern Italy are both distraught and mystified. As emphasized in news reports, that region had not experienced a significant earthquake for hundreds of years. Yet, this industrial valley stretches between the Apennines and the Alps, mountain ranges that owe their very existence to the collision of the African and Eurasian Plates.

This tectonic collision, though too gradual to witness during our brief life span, has been going on for at least 40 million years, producing the varied landscape of southern Europe. A quiescent period of seismic activity in any given area, even lasting hundreds or thousands of years, is to be expected as pressure along the collision zone shifts from one region to another. While we may understand the geologic cause for the earthquakes, our inability to accurately predict the timing of such events has become all too clear over the past few decades; nevertheless, scientists in Italy are facing manslaughter charges for their failure to predict the 2009 quake in the Apennines, east of Rome, which killed more than 300 citizens.

We humans have a tendency to blame others for the misfortunes that we endure, even when they arise from the uncontrollable and, to date, unpredictable natural forces that mold our planet. We also tend to interpret our Universe, distant galaxies or local geography, from the narrow perspective of our human life span. Anyone who resides along the active plate margins of Planet Earth cannot afford to ignore the realities of its past and ongoing geologic evolution, however remote the risk of catastrophe might seem at the present time. After all, the Africa-Eurasian collision has been underway for 40 million years, 400 times longer than our own species has walked the planet.

River Relief

Those of us who frequently travel across the Great Plains or the Glaciated Plain of the Upper Midwest are usually glad to encounter river valleys, which break the monotony of the flat terrain. In these areas, the primary channel and its tributaries have carved a mosaic of hills, ridges and valleys from the plain, necessitating dips and curves in the route of our journey.

Beyond the topographic relief, these river valleys harbor rich, moist soil, supporting a wide variety of vegetation, offering a sharp contrast from the cropfields, grasslands and sparse woodlands of the adjacent plains. Visually appealing to human travelers, these corridors also attract regional wildlife that utilize them to nest, roost, feed or to escape the harsh conditions on the plain. Indeed, naturalists know that wildlife viewing is significantly more productive along these ribbons of life than it is on the flat terrain that surrounds them; even open-country species tend to congregate near river valleys, a vital source of water and cover.

Of course, river corridors also appeal to those of us who take an interest in regional topography, providing insight into the evolution of Earth's landscape. Unless one is a robotic traveler, oblivious to the environment through which they move, rivers, like mountain ranges and lakes, give us a sense of place and direction, a natural perspective by which to gauge our progress.

Superior's Northwest Coast

Just north of downtown Duluth, Interstate 35 ends and becomes Minnesota Route 61 that hugs the northwest coast of Lake Superior, all the way to the Canadian border. Providing spectacular and ever-changing views of the lake, this road also yields access to a chain of State Parks, most of which surround rivers that rise in the hill country to the west and rumble down to Lake Superior.

A few of these Parks deserve special mention. Gooseberry River State Park, a few miles north of Two Harbors, is accessed by an excellent network of trails that lead past a series of beautiful waterfalls, lead out to cliff-top views of the lake and river valley or take the visitor down to the rocky shore. Temperance River State Park, just north of Taconic Harbor, provides spectacular evidence of the erosive force of moving water; this turbulent stream has cut a deep, rugged gorge through the Precambrian volcanic bedrock, producing waterfalls, whirlpools and polished rock formations. Just shy of the Canadian border, Grand Portage State Park, stretching along the Pigeon River, provides access to Pigeon River Falls, the highest waterfall in Minnesota (120 feet). Finally, a scenic rest-stop, a few miles north of the town of Grand Portage, offers an awe-inspiring view of Lake Superior, its coastal hills, the offshore Susie Islands and the distant silhouette of Isle Royale, stretching across the northeastern horizon.

While towns, marinas, resorts and industrial ports are also spaced along Superior's Northwest Coast, they do not begin to detract from its fabulous natural landscape and the abundance of State Parks, State Forests and dedicated Wilderness could keep any naturalist entertained for months, if not years. Our only regret is that we had too little time to explore that scenic wonderland.

Western Lake Superior

Facing an off-week and yearning to get back to the North Country after our memorable journey across the Upper Peninsula of Michigan, last September, my wife and I decided to head for western Lake Superior. We left Columbia yesterday afternoon, driving north across the Glaciated Plain of northern Missouri and eastern Iowa, stopping for the night in Iowa City. This morning, we resumed our journey, dropping into the Mississippi Valley at Marquette, Iowa, and then paralleling the broad river and its wooded islands along the Wisconsin (eastern) shore. Scenic bluffs rise along both sides of the Mississippi Valley in this "Driftless Area" of the Upper Midwest, which was spared the erosive force of Pleistocene Glaciers.

Protected within the Upper Mississippi National Wildlife Refuge, access to the Mississippi and its varied riparian habitats is rather limited (except for boaters). However, Goose Island County Park, just south of La Crosse, Wisconsin, provided an excellent opportunity to study the floodplain wetlands, backwater bays and eastern channel of the river; birding was excellent at the Park. North of La Crosse, we cut away from the Mississippi for a more direct route to Duluth, Minnesota, where we are spending the night on that city's restored waterfront.

In the coming days, we plan to explore the northwest coast of Lake Superior and the Apostle Islands region of northern Wisconsin. So far, wildlife encounters have been limited to bald eagles, sandhill cranes, common loons, gulls, aquatic turtles and a host of waterfowl and songbird species. But we are now in wolf and moose country and I look forward to the possibility of seeing (or hearing) those North Country residents amidst the spectacular landscape that adjoins America's grandest Lake.

The Eurasian Mountain Arc

Looking at a map of Earth, one sees a complex of mountain ranges from Southeast Asia to Spain. Almost all of these ranges are relatively young, having crumpled skyward throughout the Tertiary Period; in fact, all are still rising today, a fact made evident by frequent earthquakes across this swath of landscape.

About 55 million years ago (MYA), soon after the Rocky Mountains formed in North America, the Indian Subcontinent began to collide with southern Asia, forcing up the Himalayas and its associated ranges, from southern China to Afghanistan. By 40 MYA, the Red Sea and Gulf of Aden began to open, splitting the Arabian Plate from Africa and pushing it northward into southwestern Asia; this compressed the crust of that region, lifting the ranges of Iran, eastern Turkey and the Middle East. About the same time, as the Tethys Sea was closing, Africa drifted northward to collide with southern Europe; this has crumpled up the Alps and its associated ranges, from western Turkey and Greece to the Pyrenees of Spain. In concert, regional subduction of the African Plate beneath the Eurasian Plate has produced a chain of volcanos along the western edge of Italy.

In some areas, such as the Pyrenees, older mountain ranges, having eroded to low hills, were renewed by these Tertiary orogenies. Today, as these tectonic forces persist and the "new" mountains continue to rise, the agents of erosion combat their uplift; molded by glaciers and incised by streams, their rock dust is carried off to the sea where, millions of years in the future, it may resurface as the core of another mountain range.

The Mackenzie River

Rising at the west end of Great Slave Lake in Canada's Northwest Territories, the Mackenzie River flows northwestward for almost 1100 miles to the Beaufort Sea. Un-dammed and winding through Subarctic and Arctic wilderness, its wide, braided channel is just the final conduit of a massive watershed that covers 20% of Canada, extending from northeast British Columbia, northern Alberta, northwest Saskatchewan and the western Yukon to the massive Mackenzie River Delta, the 12th largest on our planet. If one includes its most distant tributaries, this river system exceeds 2600 miles in length (the longest in Canada) and drains a watershed of almost 700,000 square miles.

To the southwest, the Peace and Athabaska Rivers rise on the east side of the Continental Divide in the northern Canadian Rockies; these large streams merge to form a large inland delta along Lake Athabaska, which drains to Great Slave Lake via the Slave River. Leaving Great Slave Lake, the Mackenzie River picks up meltwaters from the Mackenzie Mountains (to its west) via the Liard River system and then receives flow from Great Bear Lake, to its east, the largest lake in Canada. At its braided delta, just east of the Richardson Mountains, the Mackenzie discharges copious amounts of relatively warm, fresh, nutrient-rich water into the Arctic Ocean; this annual discharge, the 14th largest on Earth, dramatically affects the regional ecosystem, allowing boreal woodlands to extend well north of their usual range and increasing the diversity of plants and animals across the ever-changing delta. Beluga whales gather here in spring to molt in the mild river current and the countless, shallow lakes provide ideal breeding habitat for shorebirds, tundra swans and snow geese. Resident mammals include black bears, barren ground grizzlies, Arctic fox, Arctic wolves, caribou, moose, musk ox and a massive number of muskrats.

However, all is not well in this seemingly pristine wilderness. Dams on tributaries of the Mackenzie have reduced flow through its primary channel and are diminishing the annual floods that are crucial to the welfare of its delta ecosystem. In addition, worrisome levels of mercury have been found in the river over the past few years, the product of mining and power plant effluent across the watershed. Of course, as with other Arctic ecosystems, global warming may dramatically affect the natural diversity of this magnificent yet fragile landscape.

Wildlife of Afghanistan

Based on television images beamed to the world over the past few decades, Afghanistan appears to be a desolate region of rock and sand, a landscape of drought and human carnage. Yet, Afghanistan hosts a spectacular diversity of wildlife and many of its species have been threatened by the recurrent and protracted wars that have ravaged this country.

Among these threatened species are the reclusive snow leopard, markhors (large wild goats), Marco Polo sheep, urials (another wild sheep) and Asiatic black bears. Other native mammals include ibex, gray wolves, leopard cats, caracals, Pallas's cat, stone martens, lynx, Eurasian otters and Kashmir cave bats. At least 500 species of birds have been observed in Afghanistan, 200 of which breed in the country. Raptors include lammergeiers (large vultures), amur falcons, Eurasian eagle-owls and nine species of eagles, including Pallas's fish eagle. Other birds of note include grey herons, Dalmatian pelicans, black storks, greater and lesser flamingos, Himalayan snowcocks,, Demoiselle cranes, great bustards, pheasant-tailed jacanas and whiskered terns. Afghanistan hosts 3 species of bee-eaters, 7 species of sandgrouse, 8 species of shrike, 5 species of wagtail and 3 species of parakeet.

Indeed, when it comes to birds, Afghanistan rivals the Lower 48 of the U.S. in its diversity of species, though migrant and wintering birds account for the majority of its population. But when we consider the wide range of habitat on our Continent compared with the landlocked deserts and mountainous terrain of Afghanistan, its diversity of birds is truly impressive, reflecting the fact that Afghanistan, long a crossroads for human trade and migration, remains an important crossroads for avian travel.

Natural Afghanistan

For the past decade, Afghanistan has evoked images of war, political corruption and civil strife. It seems appropriate to shift gears and focus on the natural landscape of that isolated but starkly beautiful region of our planet.

Consulting a map, one finds that the country of Afghanistan is pear-shaped, aligned northeast to southwest; the narrower part, complete with a thin stem of territory that pokes eastward to China, is to the northeast while its broader portion is to the southwest, abutting Iran, western Pakistan and southern Turkmenistan. The high spine of the Hindu Kush, the westernmost extension of the Himalayas, bisects the northeastern half of the country, curving from its northeastern frontier to the heart of Afghanistan; some peaks in easternmost Afghanistan soar above 25,000 feet while elevations gradually decrease toward the west. On either side of this natural divide, numerous streams have carved a maze of ridges, canyons and valleys from the Hindu Kush massif, giving rise to four major river systems.

The Kabul River drains the southeast edge of the Hindu Kush, flowing through the capitol city before cutting through the Spin Ghar Range along the border with Pakistan, where it joins the Indus River. The Helmand River and its tributaries drain the southwestern and western flanks of the Hindu Kush, crossing the southwest plateau region of Afghanistan and eventually flowing westward into Iran. The Hari Rud, rising along the northwest side of the massif, also flows westward into Iran while the Amu Darya, fed by mountain glaciers of the Hindu Kush, snakes westward across the fertile plain of northern Afghanistan, forming its border with Tajikistan, Uzbekistan and Turkmenistan (east to west) before angling northwestward into the latter country. With the exception of the Kabul River, which reaches the sea via Pakistan's massive Indus River system, the rivers of Afghanistan, heavily utilized for irrigation in this dry landscape, eventually disappear into the desert sands of Iran and Turkmenistan.

The Illinois Basin

Like the Michigan and Permian Basins, the Illinois Basin is a structural bowl of Precambrian basement rock within which younger layers of sedimentary rock have accumulated. This bowl, which covers the southern 75% of Illinois, the southwestern 40% of Indiana, western Kentucky and a small portion of northwest Tennessee, is surrounded by structural "arches," uplifts of the deep, ancient Precambrian rock; these include the Kankakee Arch to the northeast, the Cincinnati Arch to the southeast, the Wisconsin Arch to the north, the Mississippi River Arch to the northwest, the Ozark Uplift to the west and the Pascola Arch to the southwest.

Three miles deep at its center, this broad basin of Precambrian rock, 1.3 billion years old, accumulated layers of sediment throughout much of the Paleozoic Era (from 600 to 270 million years ago); the great majority of these deposits occured within shallow seas, which invaded and retreated from the basin at least 50 times during that period, while others were carried in by streams or deposited within vast wetlands. As the basin filled in from the Cambrian to the Pennsylvanian Periods, these layers of sediment dipped from the surrounding arches toward the center of the structural depression; at the surface, older sediments are thus found at the periphery of the basin while the youngest (Pennsylvanian) cover its center. Following this prolonged period of deposition, which was intermittently disrupted by uplift and erosion, the Illinois Basin has undergone surface molding by the Pleistocene Glaciers and numerous streams; the glaciers flattened northern portions of the basin and coated them with a thick layer of glacial till while streams have carved southern portions into a maze of hills and valleys.

Travelling across the Illinois Basin today, one sees no evidence of the Precambrian bowl that underlies the region; indeed, its edge only outcrops in limited areas of southern Wisconsin and southeastern Missouri. Glacial erosion and till have produced the flat, productive Corn Belt across much of Illinois and western Indiana while Carboniferous sediments of the basin have been mined for their coal and drilled for their oil. As in most regions of our globe, the surface topography of the Illinois Basin only hints at the miles of sediment and complex geologic formations that lie below.