Climate: mostly temperate, but tropical in Hawaii and Florida, arctic in Alaska, semiarid in the great plains west of the Mississippi River, and arid in the Great Basin of the southwest; low winter temperatures in the northwest are ameliorated occasionally in January and February by warm chinook winds from the eastern slopes of the Rocky Mountains
Terrain: vast central plain, mountains in west, hills and low
mountains in east; rugged mountains and broad river valleys in
Alaska; rugged, volcanic topography in Hawaii
Elevation extremes:
lowest point: Death Valley -86 m
highest point: Mount McKinley 6,194 m
Natural resources: coal, copper, lead, molybdenum, phosphates,
uranium, bauxite, gold, iron, mercury, nickel, potash, silver,
tungsten, zinc, petroleum, natural gas, timber
Land use:
arable land: 19%
permanent crops: 0%
permanent pastures: 25%
forests and woodland: 30%
other: 26% (1993 est.)
Irrigated land: 207,000 sq km (1993 est.)
Natural hazards: tsunamis, volcanoes, and earthquake activity around Pacific Basin; hurricanes along the Atlantic and Gulf of Mexico coasts; tornadoes in the midwest and southeast; mud slides in California; forest fires in the west; flooding; permafrost in northern Alaska, a major impediment to development
Environment—current issues: air pollution resulting in acid rain in both the US and Canada; the US is the largest single emitter of carbon dioxide from the burning of fossil fuels; water pollution from runoff of pesticides and fertilizers; very limited natural fresh water resources in much of the western part of the country require careful management; desertification
Environment—international agreements:
party to: Air Pollution, Air Pollution-Nitrogen Oxides,
Antarctic-Environmental Protocol, Antarctic Treaty, Climate Change,
Endangered Species, Environmental Modification, Marine Dumping,
Marine Life Conservation, Nuclear Test Ban, Ozone Layer Protection,
Ship Pollution, Tropical Timber 83, Tropical Timber 94, Wetlands,
Whaling
signed, but not ratified: Air Pollution-Persistent Organic
Pollutants, Air Pollution-Volatile Organic Compounds, Biodiversity,
Climate Change-Kyoto Protocol, Desertification, Hazardous Wastes
Geography—note: world's third-largest country (after Russia and
Canada)