5,900 km). Its mouth forms the port of New Orleans, the chief port on the south. The Mississippi and its branches afford 1,000 of kilometres of navigable water. Its most important tributaries are: the Missouri, the Ohio (the most navigated river of the USA), the Red river, Arkansas. Together with its principal tributary - the Missouri, the Mississippi is over 6,000 kms long. The Mississippi system forms one of the largest navigation systems in the world (It's the third longest river system in the world). Another river that flows into the Gulf of Mexico is the Rio Grande, which forms the boundary between the U.S. and Mexico.
 rivers flowing into the Pacific Ocean
There is the Columbia on the north and the Colorado on the south. They provide navigation, hydroelectric power. A smaller river entering the Pacific Ocean is the Sacramento.

LAKES
The Great Lakes Region contains of 5 lakes: Ontario, Erie, Huron, Michigan and Superior. All of them are navigable and Lake Superior is the second largest lake in the world (after the Caspian Sea). The deepest lake is Oregon, a craterlake with a depth of 580 m).
The river Niagara, flowing from Lake Erie into Lake Ontario, is famous for the Niagara Falls, a major tourist attraction. The American part of the falls is almost 55 m high and 320 m wide. The Canadian part, the Horseshoe Fall, is 900 m wide. The two parts are separated by Goat Island.

LANDUSE FROM 1992
 cropland 25,8%
 forestland 26,6%
 pastureland 8,5%
 mountainland 12,2%
 mostly spread urban areas
 coastline 19,900,000 km (Alaska & Hawaii)

NATURAL RESOURCES
The country is rich for natural resources in petroleum, copper, lead, zinc and aluminium, coal and iron ore as well as in gold, silver and platinum,...

PETROLEUM - extracted near the Gulf of Mexico (in Texas), Louisiana, Oklahoma, California.

COAL - two principal coal-mining areas:
1) on the north - Appalachians, West Virginia, Kentucky, Ohio (60% of U.S. production)
2) on the south - Lake Michigan, Illinois, Indiana (20% of U.S. production)

IRON ORE - Lake Superior, Appalachians and Cordilleras

NON-FERROUS and precious METALS: copper, aluminium, zinc, lead, nickel, silver, gold, platinum are mined in the western Rocky Mountains.

NATURAL GAS as petroleum, sulphur is extracted in Texas, Louisiana and phosphates in Florida.

CLIMATE
In the USA there are big variations of climate.