Section B　Geography of the United States of America

The United States of America or the U. S. A. is a country in the Northern Hemisphere, Western Hemisphere, and the Eastern Hemisphere. It consists of forty-eight contiguous states in North America, Alaska, a peninsula which forms the most northwestern part of North America, and Hawaii, an archipelago in the Pacific Ocean. There are several U. S. territories in the Pacific and Caribbean. The term "United States" , when used in the geographical sense, means the continental U. S., Alaska, Hawaii, Puerto Rico, Guam, and the Virgin Islands of the U. S.. The country shares land borders with Canada and Mexico and maritime (water) borders with Russia, Cuba, and the Bahamas in addition to Canada and Mexico.

1. Physical Geography

The United States of America may be divided into seven broad physiographic divisions from east to west: the Atlantic Plain, the Appalachian Highlands, the Interior Plains, the Interior Highlands, the Rocky Mountain System, the Intermountain Region, and the Pacific Mountain System.

The Atlantic Plain

The Atlantic Plain is a rather flat stretch of land that borders the Atlantic Ocean (including the Gulf of Mexico). It is approximately 2,200 miles long, stretching from Cape Cod, through the southeast U. S. and through Mexico, ending with the Yucatan Peninsula. The western border of the coastal plain is easily defined by a long series of mountain ranges, including the Appalachian Mountains and the Great Smoky Mountains. The eastern border isn't well defined since most of the plain is at or below the sea level. Some define the east border to be the coastline. Currently, the coastal plain is very wet, including many rivers, marshes and swamplands. It is primarily used for agriculture.

The Appalachian Highlands

Appalachian Highlands, an upland area of eastern North America, chiefly in the U. S., extends from eastern Canada to central Alabama. The entire system is almost 2,000 miles (3,200 km) long, and up to 300 miles (480 km) wide. The region's higher and rougher parts form the so-called Appalachian Mountains.

The Appalachians first formed roughly 480 million years ago during the Ordovician Period, and once reached elevations similar to those of the Alps and the Rocky Mountains before they were eroded. The Appalachian chain is a barrier to east-west travel as it forms a series of alternating ridgelines and valleys oriented in opposition to any road running east-west. The scenic beauty of mountains, streams, forests and the region's historic sites make the Appalachians a popular vacation area.

The Interior Plains

The Interior Plains, the largest physical region in the U. S., are located west of the Appalachian Highlands, east of the Rocky Mountains, and north of the Gulf Coastal Plain. The region's greatest dimensions are about 1,200 miles (1,900 km) east-west and 1,300 miles (2,100 km) north-south. Thick beds of sedimentary rocks underlie this vast area of plains. North of the Missouri and Ohio rivers are deep glacial deposits.

At about the 100th meridian, the Interior Plains divide into the Great Plains, to the west, and the Central Lowlands, to the east. Both sections have vast stretches of flat land and of gently rolling land. A major difference between the two areas is elevation—the Great Plains lie at an elevation of 2,000 to 6,000 feet (600 to 1,800m), and the Central Lowlands are much lower. The Interior Plains are bordered by two upland regions—the Superior Uplands on the north, and the Central Uplands on the south. The Superior Uplands are in Minnesota, Wisconsin, and Michigan. The Central Uplands are in Missouri, Arkansas, and Oklahoma.

The Interior Highlands

The U. S. Interior Highlands is a mountainous region spanning eastern Oklahoma, western and northern Arkansas, southern Missouri, and the extreme southeast corner of Kansas. The area refers to the combined mountainous region of the Ozarks and Ouachita Mountains, which form a distinct physiographic division. It is the only major highland region between the Rocky Mountains and the Appalachian Mountains in the U. S..

The region is occupied by the Ozark mountain forests, an ecoregion of temperate broadleaf and mixed forests. Parts of the area are covered by three national forests: the Ouachita National Forest in Oklahoma and Arkansas, the Ozark-St. Francis National Forest in Arkansas, and the Mark Twain National Forest in Missouri.

The Rocky Mountain System

The Rocky Mountain Range actually represents a series of more than 100 separate mountain ranges, rather than one uninterrupted mountain chain. These ranges stretch through New Mexico, Idaho, Montana, Wyoming, Utah and Colorado, and also extend into British Columbia and Alberta, Canada. The entire series of mountain ranges measure approximately 3,000 miles. Mount Elbert near Leadville, Colorado, has an elevation of 14,433 feet, making it the tallest peak in the mountain range. The popular Pikes Peak, the second most visited peak in the world, is the 31st highest, rising 14,110 feet above the sea level.

Because of the vast expanse covered by the Rocky Mountain Range, it holds several national parks. Rocky Mountain National Park, Yellowstone National Park, Grand Teton National Park, Glacier National Park and the Royal Gorge Park, all give guests the opportunity to explore the Rockies. It also serves as the habitat to 66 mammal species, including the rare lynx and wolverine.

The Intermountain (Intermontane) Region

The Intermountain Region or the Intermountain West is located between the Rocky Mountains on the east and the Cascade Range and Sierra Nevada on the west. It covers the state of Utah and the neighboring parts of Arizona, Nevada, Colorado, western Wyoming, eastern Idaho, and a small portion of southwestern Montana.

Its wetlands, rivers, and lakes provide habitats for many birds. The Intermountain Region is a home to a massive 1. 6 million breeding ducks and over 100,000 over-wintering ducks, geese, and swans. It is thinly populated because people don't have the proper necessities to live there along with the proper food supply. This is a good thing because the land is left alone for the animals to enjoy, and it leaves the environment in a beautiful state.

The Pacific Mountain System

Between the Intermountain Region and the Pacific Ocean is the Pacific Mountain System, the series of mountain ranges that stretch along the West Coast of North America from Alaska south to Northern and Central Mexico. It runs for some 4,500 miles (7,250 km) in the U. S. and extends northward into Canada for another 1,000 miles (1,600 km). This province includes the active and sometimes dead or extinct volcanoes of the Cascade Range and the young, steep mountains of the Pacific Border and the Sierra Nevada.

The Cascade Range is a backpacker's paradise. Hikers can experience a striking ecological transition across the range, from temperate rain forests on the western, windward slopes to open pine savanna and shrub steppes on the eastern. The Sierra Nevada is a 400-mile-long mountain range of singular beauty. While the Sierra high country has its share of rugged topography, including sawtoothed volcanic ridges and some mighty river gorges, much of it offers the backpacker remarkably gentle terrain of undulating granite highlands, as well as some of the most moderate mountain weather.

2. Climate

The climate in U. S. varies across different parts of the country. Generally, the western and southern parts of U. S. have warmer weather as compared with the eastern and northern parts. The eastern and northern parts of U. S. experience chilly winters with heavy snowfalls but the summers are pleasant. The western and southern parts have extremely hot summers and comparatively tolerable winters.

The U. S. can be divided into six climate regions (Northwest Pacific, Mid/South Pacific, Midwest, Northeast, Southeast, Southwest), excluding Alaska, Hawaii and outlying territories. The climate varies considerably among different regions.

Northwest Pacific(Includes states like Oregon and Washington to the crest of the Cascade Mountains)

This is perhaps the wettest part of the country. There are scattered rain showers all year round. Temperatures are mild averaging around 40 °F(32. 2 ℃). The summer months are pleasantly warmer and never too hot. You can see fogs along the coast during the warmer weather but the fog is less dense during mid-day.

Mid/South Pacific Rockies(Includes states like California, Idaho, Montana, Wyoming, Colorado, Utah and Nevada)

These states have generally dry and delightful summers. California has excellent weather all the year round, with the northern part of the state somewhat cooler (quiet chilly in the winter but seldom freezing). There are few places in California that experience snow, and the state is known for its nice weather. Most of the cities have tolerable winters. The winter months in the other states like Montana, Idaho and Wyoming can be very cold, with temperatures dropping well below 0 °F(-17.8℃). Colorado, Utah and Nevada are known for their excellent skiing.

Midwest (Includes states like Dakotas, Kansas, Illinois, Iowa, Minnesota, Wisconsin, Michigan, and Indiana)

This region is moderately dry. Precipitation occurs mainly in late spring and early summer. Summers are pleasant but winter time can be harsh, with lots of snow and heavy chilly winds. Extremes within the Midwest can drop down to -50°F(-45.6℃).

Northeast (Includes states like Ohio, Pennsylvania, Washington D. C., and Maryland).

This entire area is moderately rainy. In winter, the region experiences heavy snow and freezing rain. Summers are usually pleasant, sunny and warm. The fall is especially beautiful in wooded areas.

Southeast(Includes states like portions of Arkansas and Louisiana, Kentucky, West Virginia, Virginia)

Like the Northeast, this entire area experiences moderate rains fairly and evenly throughout the year. The spring, summer and fall seasons are all very pleasant. Some snow and freezing rain fall in winter, but for the most parts, the winters are quite mild and short lived. Southern Florida, like California, usually has excellent weather all the year round.

Southwest(Includes states like Arizona, New Mexico, Texas, Oklahoma and western portions of Arkansas and Louisiana)

This is the hottest and high rainfall region of the U. S.. You must be prepared to face heavy rains accompanied with thunder storms, dangerous lightening and occasional tornadoes. The winters are generally short but some freezing rains do occur. The spring and fall seasons are quite long and temperatures are generally excellent. The summers are very hot with temperatures approaching and exceeding 100°F(37.8℃) on many days.