Physical Characteristics

The Cordillera is a region consisting of mountains and plateaus.

There are three mountain ranges in the Cordillera. The Rocky Mountains, which stand 4200m above sea level, are the highest range; the Cascade Range, which is made up of lava and volcanic materials and the home to Mt. St. Helens; and the Coastal Range which form the western coast of North America for approximately 4000 km. The Cascade and Coastal Ranges encountered change in 1980 when Mt. St. Helens erupted. As a result, two dozen lakes were buried, rivers were flooded and landscape was permanently changed due to the boiling rock and ash. However, mountains aren't the only landforms in the Cordillera. In fact, most of the US portion is plateau enclosed in the mountain ranges. There are three subregions of plateaus - the Columbia Plateau, Basin and Range Plateau, and Colorado Plateau. The plateaus are flatter than the mountainous regions, but they do have hills, ridges and plains. Two examples of these would be the Grand Canyon which was formed by erosion from streams and rivers, mainly the Colorado, running through it and Death Valley, which is 60 m below sea level

Bodies of Water
In the Cordillera, streams are dry most of the year, but are prone to flooding in the rainy season. Most rivers begin in the mountains and flow through the plateaus. The main rivers of the Cordillera are the Colorado, Rio Grande, and Colombia. The great divide is a line which follows the biggest points along the Rockies and divide the flow of the river, forcing it to drain out to one of the drainage areas. Most rivers either go west to the Pacific Ocean, east and north to the Arctic Ocean, or east and south to the Gulf of Mexico. Some rivers flow from the mountain and become trapped in the plateaus and form salty lakes. The water evaporates from the lake, but leaves behind the salt. The Great Salt Lake in Utah is a good example of this.

There are many types of soil in the Cordillera region. In the mountains, soil is thin and not useful for farming. Desert soil is dry and lacks organic matter, as a result not useful for farming unless irrigated. However, in the northwest, soils are fertile and good for growing grasses and grains. Some river valleys provide soil suitable for farming.

Vegetation in the Cordillera region is affected by the elevation. Forests grow at high elevations. The windward west side of a mountain has much precipitation. Cedar and Ponderosa Pine grow in these moist areas. The east side, most of the plateau subregion, is arid, resulting in desert vegetation. The cactus grows in the southern part of the plateau region (Nevada and Arizona), whereas sagebush1 grows in the northern desert and the cresote2 bush is common in the south. Juniper3 and tamarisk4 usually grow near rivers. Grasslands are found at higher elevations in the plateau region, mesquite grass, short grass and bunch grass being the most common. These grasses usually grow in New Mexico, southeastern Arizona, and Columbia Basin. At higher elevations, large trees - Ponderosa Pine and Douglas Fir - appear. Near the summit5 there are small or no trees, due to high winds and very cold temperatures. This is called the tree line - where trees give way to shrubs.

The Cordillera is an arid or semi-arid region, meaning that it recieves little precipitation. The precipitation varies from 250 mm in the plateau region, to 2500 mm in the Cascade and Coastal Ranges. Wet winds blow from the west off the Pacific Ocean rising where they reach the Coastal Mountains. As they rise, the air cools and can't hold as much moisture. The moisture condenses and falls as rain on the windward6 (west in this case) side. The leeward7(east in this case) side is dry because it is in the rain shadow. The wind travels down the mountain and picks up moisture. This is repeated over the Rockies. Therefore, the east side is quite dry, and the west gets a fair amount of moisture. Temperatures drop by 0.6 for each 100m rise. Some mountains have snow-covered summits all year round with mountain tops so cold that not all the ice melts, therefore, forming glaciers. The northern part of the Cordillera