Amur River

THE AMUR RIVER, in Siberia, springs from the confluence of the Shilka and Argun Rivers east of Lake BAIKAL and flows over 1,800 mi (2,897 km) toward the Tatar Straits, the passage between Sakhalin and the Russian Pacific Coast. With all tributaries, the Amur basin covers nearly 750,000 square mi (1,942,491 square km) of area. […]

Amu Darya

THE AMU DARYA has served as a bridge between cultures for several millennia. A river that flows straight across one of the harshest deserts in the world, it has served as a natural highway for migrants and invaders from Central Asia to South Asia and the MIDDLE EAST, as well as a boundary for the empires […]

American Samoa

AMERICAN SAMOA, a territory of the UNITED STATES in the PACIFIC OCEAN, consists of the eastern half of the Samoan archipelago and comprises five volcanic islands: the main island of Tutuila and its smaller partner, Anu'u, plus the islands of Ofu, Olosega, and Ta'u (the Manu'a Islands) to the east. The territory, with its capital […]

Amazon River

SOME AUTHORITIES believe that the river in BRAZIL and neighboring countries was named after the Amazons, women warriors of Greek mythology, who were thought to reside in the region; other scholars insist that the name is derived from the local native word amassona, meaning “boat destroyer.” Despite centuries of effort to overcome the dominance of nature, […]

Amazon Rainforest

THE AMAZON RAINFOREST is the largest rainforest in the world. It extends for 3,000 mi (4,828 km) from the ANDES mountains to the ATLANTIC OCEAN. The rainforest covers parts of BRAZIL, PERU, ECUADOR, COLOMBIA, BOLIVIA, and VENEZUELA, encompassing over a billion acres and covering one-third of South America. The 6,500 mi (10,461 km) of the […]


THE ALTIPLANO IS A high plateau located in the central ANDES region of South America at an altitude of about 13,123 ft (4,000 m). It reaches into parts of PERU, BOLIVIA, CHILE, and ARGENTINA. On the west, it bounds the Cordillera Occidental and borders the Cordillera Oriental on the east. It is surrounded by volcanoes […]

Altai Mountains

THE ALTAI MOUNTAINS are a system of remote mountains in central Asia that cover an area of 326,256 square mi (845,000 square km) bounding RUSSIA, KAZAKHSTAN, MONGOLIA, and CHINA. This system is a natural marvel that has been largely untouched by large industries and has a very sparse population. Its name is derived from the […]


THE ALPS ARE Europe's major mountain chain, occupying center stage between the  ultural and geographic regions of western, eastern, southern, and northern Europe. Stretching in an arc about 600 mi (1,000 km) from west to east, the range covers parts of FRANCE, ITALY, SWITZERLAND, LIECHTENSTEIN, AUSTRIA, and SLOVENIA, with related features extending into GERMANY, CROATIA, and […]


THE SEDIMENT DEPOSITED by rivers is called alluvium. The name derives from the Latin word alluvius, meaning “washed up.” Alluvium comprises clay, silt and sand (in some definitions gravel is included) and derives from the erosion of rocks and soils in the upper reaches of river basins. The mineral characteristics of the alluvium thus reflect […]

Alluvial fan

THE U.S. COMMITTEE on Alluvial Fan Flooding recently defined an alluvial fan as “a sedimentary deposit located at a topographic break, such as the base of a mountain, escarpment, or valley side, that is composed of streamflow and/or debris flow sediments and that has the shape of a fan either fully or partially extended.” The […]


Area 919,595 square mi (2,381,740 square km) Population 39.93 million (2014) Capital Algiers Highest Point 9,852 ft (3,003 m) Lowest Point -131 ft (-40 m) GDP $214.1 billion (2014) Primary Natural Resources petroleum and natural gas, mining. WITH MORE THAN 80 percent of its land covered by the SAHARA DESERT in northern Africa, Algeria is […]

Aleutian Islands

KNOWN AS THE Catherine Archipelago until 1900, the Aleutian Islands comprise some 150 islands in four groups, which are, in order of proximity to the mainland: the Fox, Andreanof, Rat, and Near Islands. The name probably derives from the Chukchi word aliat, meaning “island.” Geographically, the islands separate the Bering Sea from the PACIFIC OCEAN. They extend […]


Area 10,685 square mi (28,748 square km) Capital Tirana Population 2.894 million 2014 Highest Point Maja e Korabit 9,085 ft (2,753 m) Lowest Point 0 m GDP $13.37 billion 2014 Primary Natural Resources petroleum, hydropower. ALBANIA IS UNIQUE in many ways. This small, mountainous nation on the western side of the Balkan Peninsula has a […]


THE 49th STATE admitted to the union in U.S. history, Alaska is located northwest of the 48 contiguous states. It borders CANADA to the east, the PACIFIC OCEAN to the south, the Bering Sea to the west, and the ARCTIC OCEAN to the north. Alaska has several distinct physical regions. The southernmost region is named the […]


THE HEART OF THE Confederate States of America during the Civil War, much of the state of Alabama was originally part of GEORGIA, its eastern neighbor in the south-central UNITED STATES. The British and French fought over the southernmost area until it was ceded to the British in the War of 1812. Scholars disagree on […]

Ahaggar Mountains

THE AHAGGAR IS a large mountainous plateau region lying on the TROPIC OF CANCER in the north-central SAHARA DESERT. It covers an area of 210,000 square mi (543,900 square km) which is about the size of FRANCE, or of ARIZONA and NEW MEXICO combined. It is about 1,000 mi (1,609 km) east of the ATLANTIC […]

Agricultural Revolution

AROUND 11,000 B.C.E., human beings began to domesticate and cultivate plants. This new activity, which eventually changed populations, lifestyles, and the environment in profound ways, proceeded in sporadic bouts. Although the development of agriculture took place over millennia on different continents, its initial beginning is sometimes referred to as the Agricultural Revolution. Archaeological evidence shows […]


Area 250,000 square mi (647,500 square km) Population 31.28 million 2014 Capital Kabul Highest Point 24,550 ft (7,485 m) Lowest Point 846 ft (258 m) GDP $20.84 billion 2014 Primary Natural Resources natural gas, petroleum. THE STATE OF AFGHANISTAN is a landlocked country that borders PAKISTAN to the south, IRAN to the west, TURKMENISTAN, UZBEKISTAN, […]


THE AFAR PEOPLE live in the rocky desert terrain of eastern Africa, in an area called the HORN OF AFRICA. Most of them live in the countries of DJIBOUTI, ETHIOPIA, and ERITREA. The territory, once known as the French Territory of the Afars and Issas, became Djibouti in 1977, when France gave the people their […]

Aegean Sea

THE AEGEAN SEA is an arm of the MEDITERRANEAN SEA, located between the Greek peninsula to the west and TURKEY to the east. The Aegean is connected through the Dardanelles, the Sea of Marmara, and the Bosporus with the BLACK SEA, while the island of Crete is considered to be the southern boundary. In all, it […]

Adriatic Sea

THE ADRIATIC SEA (in Italian “Mar Adriatico,” in Serbian “Jadransko more”) is a northwest-to-southeast arm of the MEDITERRANEAN SEA. The sea separates the Italian peninsula from the Austro-Hungarian, Montenegrin, and Albanian littorals, and the Italian Apennine Mountains from the Balkan Dinaric Alps. The western coast is Italian and the eastern comprises Slovenia, Croatia, Bosnia and […]

Aconcagua Mountain

ACONCAGUA MOUNTAIN LIES west of Mendoza, argentina, entirely within Argentina, and immediately east of Argentina's border with chile. The mountain is, at 22,834 ft (6,960 m), not only the tallest mountain in the Western Hemisphere, but also the highest outside of Asia. Its twin peaks, the northern of which is the tallest, can be seen […]


ACEH (full name: Naggroe Aceh Darussalam, meaning “the Abode of Peace”) is one of the three “special territories” among the 27 administrative provinces of indonesia. Its location, on the large island of SUMATRA in the northeast corner of the Indonesian archipelago, facing the Andaman Sea and the Straits of Melaka, makes it the closest Indonesian […]

Abyssal plain

LOCATED IN THE world's oceans, an abyssal plain is a depositional surface on the seafloor. The plain is generally 13,000 to 20,000 ft (4,000 to 6,000 m), extending seaward from the base of a continental slope or from the seaward edge of an oceanic trench to the midocean ridge. The term plain implies that this […]

Chronology of Geography

200 million B.C.E. Present-day continents were part of a supercontinent known as Pangaea or Pangea (Greek  or “all-Earth”). Over millions of years, this supercontinent broke up through the creation of rifts, cracks in the crust that moved apart and allowed magma to rise from lower levels and form new seabeds. Water moved into the broken landmass […]