ical in Hawaii and Florida and
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 coast; tornadoes in the
midwest; mud slides in California; forest fires in the west; flooding;
permafrost in northern Alaska is 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-Volatile Organic Compounds,
Biodiversity, Desertification, Hazardous Wastes

Geography-note: world's third-largest country (after Russia and
Canada)

@United States:People

Population: 270,311,756 (July 1998 est.)

Age structure:
0-14 years: 22% (male 29,952,220; female 28,560,357)
15-64 years: 66% (male 88,113,895; female 89,399,501)
65 years and over: 12% (male 14,088,571; female 20,197,212) (July 1998
est.)

Population growth rate: 0.87% (1998 est.)

Bi