Although the USA consists of large natural units, the landscape is very diverse regionally. Only the coast, with the exception of Alaska, is relatively indented. The arrangement of landforms from north to south is characteristic. This is the course of the Cordillera mountain system, the central plateau as well as the lowlands and the eastern mid-mountains. There are such great geographical differences not only between north and south, but also between west and east. The climate also varies from arctic in northern Alaska to near-tropical in Florida.
According to Diseaseslearning.com, the US lies in a region of prevailing westerly winds, but the central plains are influenced by cold northerly flow from Canada and warm, moist winds from the Gulf of Mexico. The size of the North American continent ensures that most of the US has a continental climate, characterized by cold winters, hot summers, and a wide range of daily temperatures.
The west coast is influenced by the Pacific. In the northwest, moist air brings the highest precipitation in the fall and winter to the windward regions of the states of Washington and Oregon (in the Olympia Mts. even over 3000 mm per year) and causes mild winters there. California, whose coastal region is influenced by the cold ocean current, has a significantly drier climate, and Central Valley agriculture (200–400 mm of rainfall) is heavily dependent on irrigation. In the south, in the rain shadow of the mountains (Sierra Nevada), where absolute temperatures exceed 50°C, lie the deserts of Death Valley, the Mojave Desert and others in Nevada and Arizona. All mountain plateaus and basins are dry, more precipitation falls only in the Rocky Mountains.
To the east of them lie the semiarid Grea Plains (again in the rain shadow), but further east the central plains receive more precipitation, especially in summer (up to 1200 mm) as a result of moist and warm air flowing from the Gulf of Mexico. Climatic conditions are less favorable in the Midwest, where moist air masses from the south meet cold winds blowing from the north and from the mountains. The result can be anything from thunderstorms, hail and blizzards to dust storms and tornadoes. Not surprisingly, this area also suffers from the largest temperature fluctuations throughout the year and during the day. Only the short spring and autumn are pleasant. Towards the north, the winter season with snow and frost is getting longer.
The Gulf of Mexico regions generally have mild and short winters, but are often subject to hurricanes in late summer and early fall. Equally vulnerable is the Southeast with Florida, which has a warm and humid subtropical climate almost all year round. The Appalachian Mountains receive ample rainfall (800–1200 mm) practically throughout the year. The northeastern US has a continental climate influenced more by currents from the west and north than from the ocean. Low winter temperatures together with unstable wind conditions bring heavy snowfall, while summers are hot with high humidity.
The state of Alaska is located in the far northwest of North America, bordering Canada to the east and being separated from Russia in the west by the Bering Strait.
The southernmost part of Alaska is called the Panhandle. It is a narrow strip of land along the North Pacific coast bordering Canada. It consists of a high glaciated mountain range with numerous fjords and islands. Also, the coast of the Gulf of Alaska is lined with an almost continuous chain of mountains, from which glaciers such as the Malaspina descend to sea level. The mountain range stretches in an arc from the Boundary Range in the Panhandle through the mountain ranges of the Alaska Peninsula and the Aleutian Islands.
North of the Alaska Range lies the vast central plateau, divided by the broad valleys of the Yukon River and its tributary the Tanana. In the west, the Yukon created a large floodplain dotted with thousands of lakes. In the north, the Brooks Range stretches across Alaska from the Canadian border to the Bering Strait. The coast of the Arctic Ocean is bordered by a wide plain covered with tundra.
The climate is generally cool, but varies considerably with latitude and exposure. The greatest temperature extremes occur on the drier Yukon Plateau (-55°C to 25°C). The South Coast and Aleutian Islands have a humid oceanic climate with 1000–3000 rainfall per year.
The Hawaiian Islands are actually the peaks of an undersea ridge of volcanoes that stretches in a wide arc across the middle of the Pacific Ocean. The largest of the main islands are Hawaii, Maui, Oahu and Kauai. In addition to them, there are 124 smaller islands. The climate is warm and humid. The windswept northeast slopes are among the rainiest places in the world (Waialeale on Kauai recorded a world high of 11,684 mm) and are covered with lush tropical vegetation. On the island of Hawaii there are two large volcanoes Mauna Kea (4205 m) and Mauna Loa (4170 m) and the very active crater Kilauea.
There are no native reptiles or mammals on the Hawaiian Islands, but there is an admirably diverse birdlife, mostly endemic.
During the 20th century, the USA became the most influential power in the world. The standard of living in the US is among the highest in the world, and Americans’ sense of individual freedom and entrepreneurship is widely admired.
Nevertheless, the USA has serious social and economic problems. Organized crime, political corruption, and the waste of natural resources characterize American society as much as the skill and artistry that accompanied the moon landing, medical and computer breakthroughs, the Philadelphia Symphony Orchestra, Hollywood, or Mickey Mouse.