 |
|
| ||||||||||||||||||||||||||
|
|
| ||||||||||||||||||||||||||
|
|
|
|
|
| ||||||||
The Cascade Range is a mountainous region famous for its chain of tall volcanos called the High Cascades that run north-south along the west coast of North America from British Columbia to the Shasta Cascade area of northern California. The small part of the range in British Columbia is called the Cascade Mountains.
The Cascades (as they are called for short) are part of the Pacific Ring of Fire, the ring of volcanoes around the Pacific Ocean. All of the known historic eruptions in the contiguous United States have been from Cascade volcanoes. The two most recent were Lassen Peak in 1911 and Mount St. Helens in 1980.
Native Americans have inhabited the area for thousands of years and developed their own myths and legends concerning the Cascades. According to some of these tales, Mounts Baker, Jefferson, and Shasta were used as refuge from a great flood. Other stories, such as the Bridge of the Gods tale, had various High Cascades such as Hood and Adams, act as god-like chiefs who made war by throwing fire and stone at each other. St. Helens with its pre-1980 graceful appearance, was regaled as a beautiful maiden for whom Hood and Adams feuded. Native tribes also developed their own names for the High Cascades and many of the smaller peaks.
In the spring of 1792 British navigator George Vancouver entered Puget Sound and started to give English names to the high mountains he saw. Mount Baker was named for Vancouver's third lieutenant, the graceful Mount St. Helens for a famous diplomat, Mount Hood was named in honor of Samuel Hood (a high-ranking naval officer) and the tallest Cascade, Mount Rainier, is the namesake of Admiral Peter Rainier. Vancouver's expedition did not, however, name the range these peaks belonged to. In 1805 the Lewis and Clark expedition passed through the Cascades by using the Columbia River, which for many years was the only practical way to pass that part of the range. The expedition, and the many settlers and traders that followed, met their last obstacle to their journey at the Cascades Rapids in the Columbia River Gorge, a feature on the river now submerged beneath Lake Bonneville. Before long, the great white-capped mountains that loomed above the rapids were called the "mountains by the cascades" and later simply as the "Cascades" (the earliest attested use of this name is in the writings of botanist David Douglas). On their return trip Lewis and Clarke's group spotted a high but distant snowy pinnacle that they named for the sponsor of the expedition, U.S. President Thomas Jefferson.
The Barlow Trail was the first established land path for U.S. settlers through the Cascade Range in 1845, and formed the final overland link for the Oregon Trail (previously, settlers had to raft down the treacherous rapids of the Columbia River). It passes north of Mt. Hood.
With the exception of the 1915 eruption of remote Lassen Peak in Northern California, the range was quiet for more than a century. Then, on May 18, 1980, the dramatic eruption of little-known Mount St. Helens shattered the quiet and brought the world's attention to the range. Geologists were also concerned that the St. Helens eruption would awaken other Cascade volcanoes like it did the previous century, when a total of eight erupted between 1800 and 1857. None have erupted since St. Helens, but precautions are being taken nevertheless, such as the Mount Rainier Volcano Lahar Warning System in Pierce County, Washington.
At its southern end the range is about 30 to 50 miles (50 to 80 km) wide and 4500 to 5000 feet (1370 to 1520 m) high but is higher and 80 miles (130 km) wide in northern Washington. The tallest volcanoes of the Cascades (called the High Cascades) dominate the rest of the range, often standing twice the height of the surrounding mountains and thus often have a visual height of a mile (1.6 km) or more. The tallest peaks, such as the 14,410 foot (4392 m) high Mount Rainier, dominate their surroundings for 50 to 100 miles (80 to 160 km).
The northern part of the range, north of Mount Rainier is extremely rugged, with many of the lesser peaks steep and glaciated. The valleys are quite low however, and major passes are only about 1000 m (3300 ft) high.
Because of the range's proximity to the Pacific Ocean, precipitation is substantial, especially on the western slopes, with annual accumulations of up to 150 inches (380 cm) in some areas and heavy snowfall as low as 2000 feet (610 m). Most of the High Cascades are therefore white with snow and ice year-round. The western slopes are densely covered with Douglas fir, Western hemlock and alder, while the drier eastern slopes are mostly pine, with Western larch at higher elevations. Annual rainfall drops to 8 inches (20 cm) on the eastern foothills due to a rainshadow effect.
Beyond the foothills is an arid plateau that was created 16 million years ago as a coalescing series of layered flood basalt flows. Together these sequences of fluid volcanic rock form a 200,000 square mile (520,000 km2) region out of western Washington, Oregon, and parts of Northern California and Idaho called the Columbia River Plateau .
The gorge created by the Columbia River is the only major break in the American part of the Cascades. When the Cascades started to rise 7 million years ago in the Pliocene, the Columbia River drained the relatively low Columbia River Plateau. As the range grew, the Columbia was able to keep pace, creating the gorge and major pass seen today. The gorge also exposes uplifted and warped layers of basalt from the plateau.
Another major pass was cut by the Fraser River through mainly non-volcanic rocks in the British Columbian part of the range. This group of mountains are often called the "Coast Mountains" but are in fact structurally part of the Cascades. Mount Garibaldi and its associated group of volcanoes are in this part of the range. The country rocks here were derived from a mini-continent that grafted itself to this part of North America 50 million years ago, carrying along its own subduction zone (see Juan de Fuca Plate).
See also: Map of the Southern Oregon Cascade Range
Soil conditions for farming are generally excellent, especially downwind of volcanoes. This is largely due to the fact that volcanic rocks are often rich in minerals such as potassium and decay easily. Volcanic debris, especially lahars, also have a leveling effect and the storage of water in the form of snow and ice is also important. Much of that water eventually flows into reservoirs where it is used for recreation before its potential energy is captured to generate hydroelectric power before being used to irrigate crops.
In addition, there is a largely untapped amount of geothermal power that can be generated from the Cascades. The USGS Geothermal Research Program has been investigating this potential. Some of this energy is already being used in places like Klamath Falls, Oregon where volcanic steam is used to heat public buildings. The highest recorded temperature found in the range is 510° F (265° C) at 3075 feet (937 m) below Newberry Caldera's floor.
(listed north to south)
There are four national parks in the Cascade Range and many national monuments, wilderness areas, and national forests. Each classification protects the various glaciers, volcanoes, geothermal fields, rivers, lakes, and forests to varying degrees.
|
||||
| View Live Article | This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License | |
||
