Summary

The Cascadian Federation is a nation-state as diverse in its geography as it is diverse in its nationalities. Cascadia is dominated by several mountain ranges, including the Cascade Range, the Olympic Mountains and the Rocky Mountains. The highest point in the Federation is Mt. Rainier, in the Snoqualmie section of the Cascade Range, at 14,410 feet (4,392 m). Immediately inland from the Cascade Range there is a broad plateau, narrowing progressively northwards, and also getting higher. The Columbia River Plateau is a semi-arid province; and was the scene of massive ice-age floods (Glacial Lake Missoula and the Channeled Scablands), as a consequence there are many coulees, canyons, and plateaus. The Columbia River cuts a deep and wide gorge around the rim of the Columbia Plateau, and through the Cascade Range on its way to the Pacific Ocean. After the Mississippi, more water flows through the Columbia than any other river in Central North-America.

As of 11 December 2008, harmonic tremors have been detected by the Cascadan Federation Geological Survey's Cascade Volcano Observatory (CFGS-CVO) beneath Mt Hood, a volcano in the Klamath section of the Cascade Range.

Because many areas have plentiful rainfall, the Cascadian Federation has some of North America's most lush and extensive forests, and at one time, the largest trees in the world. Coastal forests in some areas are classified as temperate rain forest, or in some local slang, "cold jungle". The major metro areas of Portland-Vancouver, and Seattle-Tacoma all began as seaports supporting the logging, mining, and farming industries of the region, but have developed into major technological and industrial centers (such as the Silicon Forest), which benefit from their location on the Pacific Rim.

Cascade Range

The Cascades Province forms an arc-shaped band extending from southwestern British Columbia to Northern California, roughly parallel to the Pacific coastline. Within this region, nearly 20 major volcanic centers lie in sequence like a string of explosive pearls.

Although the largest volcanoes like Mount St. Helens get the most attention, the Cascade Volcanic Arc is really made up of a band of thousands of very small, short-lived volcanoes that have built a platform of lava and volcanic debris. Rising above this volcanic platform are a few strikingly large volcanoes that dominate the landscape. The Cascade volcanoes define the Pacific Northwest section of the Ring of Fire, an array of volcanoes that rim the Pacific Ocean. The Ring of Fire is also known for its frequent earthquakes. The volcanoes and earthquakes arise from a common source: subduction. Beneath the Cascade Volcanic Arc, a dense oceanic plate plunges beneath the North American Plate; a process known as subduction. As the oceanic slab sinks deep into the Earth's interior beneath the continental plate, high temperatures and pressures allow water molecules locked in the minerals of solid rock to escape. The water vapor rises into the pliable mantle above the subducting plate, causing some of the mantle to melt. This newly formed magma rises toward the Earth's surface to erupt, forming a chain of volcanoes (the Cascade Volcanic Arc) above the subduction zone.

A close-up look at the Cascades reveals a more complicated picture than a simple subduction zone. Not far off the coast of the North Pacific lies a spreading ridge; a divergent plate boundary made up of a series of breaks in the oceanic crust where new ocean crust is created. On one side of the spreading ridge new Pacific Plate crust is made, then moves away from the ridge. On the other side of the spreading ridge the Juan de Fuca and Gorda Plates move eastward.

There are some unusual features at the Cascade subduction zone. Where the Juan de Fuca Plate sinks beneath the North American Plate there is no deep trench, seismicity (earthquakes) are fewer than expected, and there is evidence of a decline in volcanic activity over the past few million years. The probable explanation lies in the rate of convergence between the Juan de Fuca and North American Plates. These two plates converge at 3-4 centimeters per year at present. This is only about half the rate of convergence of 7 million years ago. The small Juan de Fuca Plate and two platelets, the Explorer Plate and Gorda Plate are the meager remnants of the much larger Farallon oceanic plate. The Explorer Plate broke away from the Juan de Fuca about 4 million years ago and shows no evidence that it is still being subducted. The Gorda platelet split away between 18 and 5 million years ago and continues to sink beneath North America. The Cascade Volcanic Arc made its first appearance 36 million years ago, but the major peaks that rise up from today's volcanic centers were born within the last 1.6 million years. More than 3000 vents erupted during the most recent volcanic episode that began 5 million years ago. As long as subduction continues, new Cascade volcanoes will continue to rise.

The area is also seismically active. The Juan de Fuca Plate is capable of producing megathrust earthquakes of moment magnitude 9: the last such earthquake was the 1700 Cascadia earthquake, which produced a tsunami in Japan, and may have temporarily blocked the Columbia River with the Bonneville Slide. More recently, in 2001, the Nisqually earthquake (magnitude 6.8) struck 10 miles (16 km) northeast of Olympia, Snoqualmie, causing some structural damage and panic.

Columbia Plateau

The Columbia Plateau province is enveloped by one of the world's largest accumulations of lava. Over 500,000 km² of the Earth's surface is covered by it. The topography here is dominated by geologically young lava flows that inundated the countryside with amazing speed, all within the last 17 million years. Over 170,000 cubic kilometers of basaltic lava, known as the Columbia River basalts, covers the western part of the province. These tremendous flows erupted between 17-6 million years ago. Most of the lava flooded out in the first 1.5 million years: an extraordinarily short time for such an outpouring of molten rock. The Snake River Plain stretches across Klamath (Cascadia), through northern Nevada (United States), southern Yakima (Cascadia), and ends at the Yellowstone Plateau in Yellowstone (Cascadia). Looking like a great spoon scooped out the Earth surface, the smooth topography of this province forms a striking contrast with the strong mountainous fabric around it. The Snake River Plain lies in a distinct depression. At the western end, the base has dropped down along normal faults, forming a graben structure. Although there is extensive faulting at the eastern end, the structure is not as clear.

Like the Columbia River region, volcanic eruptions dominate the story of the Snake River Plain in the eastern part of the Columbia Plateau Province. The earliest Snake River Plain eruptions began about 15 million years ago, just as the tremendous early eruptions of Columbia River Basalt were ending. But most of the Snake River Plain volcanic rock is less than a few million years old, Pliocene age (5-1.6 million years ago) and younger. In the west, the Columbia River Basalts are just that:almost exclusively black basalt. Not so in the Snake River Plain, where relatively quiet eruptions of soupy black basalt lava flows alternated with tremendous explosive eruptions of rhyolite, a light-colored volcanic rock. Cinder cones dot the landscape of the Snake River Plain. Some are aligned along vents, the fissures that fed flows and cone-building eruptions. Calderas, great pits formed by explosive volcanism, and low shield volcanoes, and rhyolite hills are also part of the landscape here, but many are obscured by later lava flows. Evidence suggests that some concentrated heat source is melting rock beneath the Columbia Plateau Province. At the base of the lithosphere (the layer of crust and upper mantle that forms Earth's moving tectonic plates). In an effort to figure out why this area, far from a plate boundary, had such an enormous outpouring of lava, scientists established hardening dates for many of the individual lava flows. They found that the youngest volcanic rocks were clustered near the Yellowstone Plateau, and that the farther west they went, the older the lavas. Although scientists are still gathering evidence, a probable explanation is that a hot spot, an extremely hot plume of deep mantle material, is rising to the surface beneath the Columbia Plateau Province. Geologists know that beneath Hawaii and Iceland, a temperature instability develops (for reasons not yet well understood) at the boundary between the core and mantle. The concentrated heat triggers a plume hundreds of kilometers in diameter that ascends directly through to the surface of the Earth. When the hot plume arrives at the base of the lithosphere, some of the lighter rock of the lithosphere rapidly melts. It is this molten lithosphere that becomes the basalt lavas that gush onto the surface to form the Columbia River and Snake River Plain basalts. The track of this hot spot starts in the west and sweeps up to Yellowstone Volcanic National Park. The steaming fumaroles and explosive geysers are ample evidence of a concentration of heat beneath the surface. The hotspot is probably quite stationary, but the North American plate is moving over it, creating a superb record of the rate and direction of plate motion.

Ice Age Floods

With the beginning of the Pleistocene time (about one million years ago), cooling temperatures provided conditions favorable for the creation of continental glaciers. Over the centuries, as snowfall exceeded melting and evaporation, a great accumulation of snow covered part of the continent, forming extensive ice fields. This vast continental ice sheet reached a thickness of about 4,000 feet (1,200 m) in some areas. Sufficient pressure on the ice caused it to flow outward as a glacier. The glacier moved south out of Canada, damming rivers and creating lakes in Snoqualmie, Yakima, and Missoula. The ice blocked the Clark Fork River, forming the huge Glacial Lake Missoula. The lake measured about 7 770 km² (3,000 square miles) and contained about 2100 cubic kilometers (500 cubic miles), half the volume of Lake Michigan.

Glacial Lake Missoula eventually broke through the ice dam, allowing a tremendous volume of water to rush across northern Missoula and into eastern Snoqualmie. Such catastrophic floods raced across the southward-dipping plateau a number of times, etching the coulees which characterize this region, now known as the channeled scablands. As the floods in this vicinity raced southward, two major cascades formed along their course. The larger cataract was that of the Upper Coulee, where the river roared over an 800-foot (240 m) waterfall. The eroding power of the water plucked pieces of basalt from the precipice, causing the falls to retreat 20 miles (32 km) and self-destruct by cutting through to the Columbia River valley near what is now the Grand Coulee Dam.

The other major cataract is now known as Dry Falls. It started near Soap Lake, where less resistant basalt layers gave way before the great erosive power of this tremendous torrent and waterfalls developed. As in the Upper Coulee, the raging river yanked chunks of rock from the face of the falls and the falls eventually retreated to their present location. Dry Falls is three and one-half miles wide, with a drop of more than 400 feet (120 m). By way of comparison, Niagara Falls, one mile (1.6 km) wide with a drop of only 165 feet (50 m), would be dwarfed by Dry Falls.

North Cascades

The North Cascade Range in Snoqualmie is part of the American cordillera, a mountain chain stretching more than 12,000 miles (19,000 km) from Tierra del Fuego to the Alaska Peninsula, and second only to the Alpine-Himalayan chain in height. Although only a small part of the Cordillera, mile for mile, the North Cascade Range is steeper and wetter than most other ranges in North America. In geology, the range has more in common with the Coast Ranges of British Columbia and Alaska than it does with its Cordilleran cousins in the Rocky Mountains or Sierra Nevada. Although the peaks of the North Cascades do not reach great elevations (high peaks are generally in the 7,000 to 8,000-foot (2,400 m) range), their overall relief, that is, the relatively uninterrupted vertical distance from valley bottom to mountain top, is commonly 4,000 to 6,000 feet. Rocks of the North Cascades record at least 400 million years of history: time enough to have collected a jumble of different rocks. The range is a geologic mosaic made up of volcanic island arcs, deep ocean sediments, basaltic ocean floor, parts of old continents, submarine fans, and even pieces of the deep subcrustal mantle of the earth. The disparate pieces of the North Cascade mosaic were born far from one another but subsequently drifted together, carried along by the tectonic plates that make up the Earth's outer shell. Over time, the moving plates eventually accreted the various pieces of the mosaic onto the western side of North America. As if this mosaic of unrelated pieces were not complex enough, some of the assembled pieces were uplifted, eroded by streams, and then locally buried in their own eroded debris; other pieces were forced deep into the Earth to be heated and squeezed, almost beyond recognition, and then raised again to view. About 35 million years ago, a volcanic arc grew across this complex mosaic of old terranes. Volcanoes erupted to cover the older rocks with lava and ash. Large masses of molten rock invaded the older rocks from below. The volcanic arc is still active today, decorating the skyline with the cones of Mount Baker and Glacier Peak.

The deep canyons and sharp peaks of today's North Cascades scene are products of profound erosion. Running water has etched out the grain of the range, landslides have softened the abrupt edges, homegrown glaciers have scoured the peaks and high valleys and, during the Ice Age, the Cordilleran Ice Sheet overrode almost all the range and rearranged courses of streams. Erosion has written and still writes it own history in the mountains, but it has also revealed the complex mosaic of the bedrock.