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 to form enclosed bodies of water such as the Gulf of Mexico and the Red Sea. A sufficiently large rift even formed the Atlantic Ocean.

2,000,000 to 18,000 B.C.E.

The last Ice Age was the most recent episode of global cooling of the Earth. Much of the world's temperate zones were alternately covered by glaciers during cool periods and uncovered during the warmer interglacial periods when the glaciers retreated.

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.

3500 B.C.E.

The development of means of transportation, dating from the invention of the wheel, made it possible for the surplus from the countryside to feed urban populations, a system that continues to the present day.

3100 B.C.E.

Egypt appeared as a unified state around 3300 B.C.E. About 3100 B.C.E., Egypt was united under Menes, who inaugurated the 30 pharaonic dynasties in which Egypt ancient history is divided: the Old and the Middle Kingdoms and the New Empire.

2600 B.C.E.

The Indus Valley civilization prospered on the river plains and vicinity in what is western India and Pakistan. The early cities began to interact, creating a common urban culture that lasted about 700 years. The inhabitants were known as the Harappan or Indus culture, and it thrived contemporaneously with those of Mesopotamia and Egypt.

1300 B.C.E.

The recorded history of China dates back some 3,300 years, although modern archaeological studies suggest still more ancient origins in a culture that flourished between 2500 and 2000 B.C.E. Centuries of migration, amalgamation, and development created a distinctive system of writing, philosophy, art, and political organization that came to be recognized as Chinese civilization.

1120 B.C.E.

Tiglath-Pileser I, the greatest of the Assyrian kings, crossed the Euphrates, defeated the kings of the Hittites, conquered Carchemish, and advanced on the coasts of the Mediterranean. He was the founder of the first Assyrian Empire.

356–323 B.C.E.

Alexander the Great created one of the most extensive empires in history, linking Greece and the Mediterranean to the Indus River and Central Asia.

384–322 B.C.E.

Aristotle hypothesized and scientifically demonstrated that the Earth had a spherical shape. Evidence for this idea came from observations of lunar eclipses.

138 B.C.E.

China's Zhang Qian sought to ally with the Yuezhi tribe in the west and set out on a journey of discovery, resulting in the Silk Road. He returned with no trade ally but with information about horses and tribes hitherto unknown. The emperor sent more expeditions in search of horses and luxuries. Although Zhang Qian is titled as the father of the Silk Road, he was not the first. Even before, Chinese merchants were providing small amounts of Chinese goods to the west via the Silk Road.

150 B.C.E.

From the second half of the 2nd century B.C.E., until the first century, the military campaigns that consolidated the Roman Empire helped the progress of geographic knowledge. The Greeks, as a mainly seafaring people, explored the coast lands; thanks to the Romans, knowledge of the inside lands also became known. The empire extended from England to the Caspian Sea and the Tigris-Euphrates Rivers and included all of North Africa.

150 B.C.E.

Ptolemy was the first to use latitude and longitude and measure them in degrees in his book Geography.

313 C.E.

The great advance of Christian expansion was the Constantine Edict in 313. From then on, Christianity became the official religion of the Roman Empire. This was the start of an alliance between the church and political power that had a great impact on the diffusion of the Christian religion in the ancient world.

400–1300

Middle Ages (5th to 13th centuries) were a time of intellectual stagnation. In Europe, the Vikings of Scandinavia were the only group of people carrying out active exploration of new lands.
In the Middle East, Arab academics began translating the works of Greek and Roman geographers starting in the 8th century and also began exploring southwestern Asia and Africa. Some of the important intellectuals in Arab geography were Al-Idrisi, Ibn Battuta, and Ibn Khaldun.

570

Mohammed heralded the birth of Islam in the area of Mecca and Medina in Saudi Arabia. His influence spread to include all of North Africa, much of Mediterranean Europe, and parts of Central Asia, India, and China.

1100s

Chinese sailing fleets extended their trading missions into the Indian Ocean. Using Calicut in southwestern India as a base, they traveled north following the coast past the Persian Gulf and the southern Arabian Peninsula before heading south to Zanzibar on Africa's east coast.

1100s–1200s

The Crusades involved European kingdoms in the domestic affairs of the Middle East, especially Jerusalem and the Ottoman Empire, centered in the city of Constantinople.

1200s

The century saw the rise of the kingdom of Mali, based upon local gold resources and trade, especially with Arabia. This set the stage for the spread of Islam south of the Sahara.

1206–1350s

The Mongols created an empire that reached from China to Jerusalem and into Southeast Asia.

1300s–1400s

The kingdom and city of Great Zimbabwe reached its height of influence, with Swahili trade along the East African coast, linking the kingdom to Oman, the Arabian Peninsula, and the coast of India.

1325

Born in Tangier, Morocco, Ibn Battuta was a famous Arab traveler and writer who explored in Africa, Europe, and Asia. Ibn Battuta's journey began in North Africa in 1325 with travels that included visits to Egypt, Syria, the Arabian Peninsula (Mecca), (northeastern) Iran, (southern) Iraq, Red Sea, Yemen, East Africa, Asia Minor, Afghanistan, India, Bengal, Indonesia, China, and Spain. His travels ended in 1353 after a journey across the Sahara and western Africa.

1350–1918

The Ottoman Empire had a greater geographic extent than the Roman Empire and emphasized trade and science (navigation, mathematics, astronomy) as well as the arts and medicine. It stretched from the Moors in Spain to India and was ultimately focused on Constantinople in today's Turkey.

1400s

From the 15th century on, when ships became the dominant medium for commercial transport, coastal sites, such as Hormuz (Persian Gulf) and Gao (western India), were the main centers for interregional trade for the Indian Ocean. The importance of overland bases returned in the 19th century, however, as new fairs and entrepots/emporia were established along railroad lines, such as Irkutsk and Vladivostok, which functioned as way stations for the Trans-Siberian Railroad.

1421–23

After nearly 400 years of sea trade with ports along the East African coast, Chinese Emperor Zhu Di commissioned Admiral Zheng He to explore and map the world. Recent archaeological findings suggest that Zheng He's great Treasure Fleet circumnavigated the globe, rounding the Cape of Good Hope in Africa and Cape Horn at the tip of South America before returning to China in 1423. It is from this voyage that Niccolo da Conti is believed to have constructed a map later used by Christopher Columbus when he set sail for the East Indies.

1400s–1600s

During the Renaissance, numerous journeys of geographical exploration were commissioned by a variety of nation states in Europe. Most of these voyages were financed because of the potential commercial returns from resource exploitation. The voyages also provided an opportunity for scientific investigation and discovery and added many significant contributions to geographic knowledge. Important explorers of this period include Christopher Columbus, Vasco da Gama, Ferdinand Magellan, Jacques Cartier, Sir Martin Frobisher, Sir Francis Drake, John and Sebastian Cabot, and John Davis. Also during the Renaissance, Martin Behaim created a spherical globe depicting the Earth in its true three-dimensional form in 1492. Prior to Behaim's invention it was commonly believed in the Middle Ages that the Earth was flat. Behaim's globe probably influenced the beliefs of explorers of that time because it suggested that one could travel around the world.

1427–1521

The Aztecs created and ruled a major empire centered in what is today's Mexico.

1438–1525

The Incas created an empire that organized and ruled much of the Andes Mountains area in South America.

1453

With the conquest of the Byzantine capital, Constantinople, under the rule of Mohammed II (1451–81), famously known as “Mehmet the Conqueror,” the Ottomans extended their dominance over much of Anatolia and South Eastern Europe.

1492

Italian Christopher Columbus, sailing under a Spanish flag, discovers the New World.

1494

Portugal and Spain sign the Treaty of Tordesillas that established the Line of Demarcation. Crossing over present-day Brazil at the approximate longitude of 48 degrees, this meridian line granted to Spain new land to the west and to Portugal the discoveries to the east. Hence, following the landing by Pedro Alvares Cabral at Porto Seguro in 1500, Portugal claimed Brazil.

1500s

The 16th century saw the rise of many great kingdoms and empires in Southeast Asia. Many were the precursors of current states or countries.

1519

On September 20, 1519, five ships, the Trinidad, San Antonio, Concepcion, Victoria, and Santiago, along with a crew of 270 men set sail under Ferdinand Magellan on a journey around the world full of mutiny, discovery, and death.

1530s

In the 1530s, Spanish conquerors subdued the Incas, bringing the Andes Mountains into Spain's New World empire. The Spanish often used systems of forced Native American labor to work in Andean silver mines. The native inhabitants did not always readily accept Spanish rule. In the 18th century, there were more than 100 native rebellions, including the great uprising led by Jose Gabriel Condoranqui in 1780.

1543

The first to proclaim that the Earth and the other planets revolved around the sun was Nicolous Copernicus, a Polish astronomer who published his theory in 1543, the year of his death. Copernicus also claimed that the Earth rotated on its axis. Additional support for Copernicus came from Johannes Kepler, a German astronomer who rejected Ptolemy's concept of circular revolution and proposed the idea of the elliptical motion of the planets. Finally, it was Galileo Galilei in Italy who demonstrated the accuracy of the Copernican theory.

1564

Gerardus Mercator was appointed court cartographer by Duke Wilhelm of Cleve. During 1564, the map Angliae Scotiae et Hiberniae nova descriptio was printed and in 1569 the great map of the world, Nova et aucta orbis terrae descriptio, in 18 sheets, was issued to help in navigation. Thanks to this work, Mercator is heralded as the founder of modern cartography.

1587–1621

The Iranian (Persian) city of Isphahan enjoyed its golden age of artistic and architectural achievement, begun under Shah Abbas during the period of the Safavid dynasty, established in Persia in 1502. Mosques, palaces, gardens and bridges were constructed; carpet-making and artistic endeavors were encouraged. Its population swelled to 600,000 and it became one of the great metropolises of the time.

1599

In Asia, chartered companies were trading for spices, textiles, and exotic merchandise like Chinese ceramics. The English East India Company was one of these and obtained a royal charter in 1599.

1603

Edo (as Tokyo was called until 1868) was founded and later became the largest city in Japan, and the largest or second-largest in the world, with a population exceeding one million by the 18th century.

1700s

The 18th century was the start of the industrial and transport revolutions—application of mechanical power to replace animal and human power and labor, leading to the rise of factories, unions, and the development of modern political philosophies.

1773

British naval captain James Cook is the first to cross the Antarctic Circle in 1773. Exploration of the region within the Antarctic Circle resumed in 1820 when the explorer Fabian Gottlieb von Bellingshausen received support from Russian Tzar Alexander I to explore the south polar region.

1788

British territorial acquisition was being consolidated in the South Pacific. Voyages to the Pacific increased British possessions with the discovery of Hawaii, French Polynesia, New Caledonia, New Zealand and the eastern Australian coast. A penal colony was established in New South Wales in 1788.

1792

One of the oldest sources of weather prediction in the United States is the Old Farmer's Almanac, an annual publication filled with advice for the self-sufficient. The Almanac claims an 80 percent success rate in forecasting the weather—18 months ahead—based on a secret formula devised by Almanac founder Robert B. Thomas around 1792.

1800

About 1800, Alexander von Humboldt, a German naturalist, noted the apparent fit of the bulge of eastern South America into the bight of Africa. On the basis of this observation, he theorized that the lands bordering the Atlantic Ocean had once been joined.

1800

Less than 3 percent of the world's population was living in cities of 20,000 or more; this increased to about 25 percent by the mid-1960s and to about 40 percent by 1980. It is estimated that now more than half of the world's population lives in the urban areas, with 90 percent living within 62 mi (100 km) of the coast or a navigable river.

1800

Napoleon's engineers revived the idea and construction of a canal linking the Mediterranean Sea and Indian Ocean (via the Red Sea). The eventual Suez Canal greatly changed maritime trade by reducing the need to go around the Cape of Good Hope at the southern tip of Africa.

1804

Meriwether Lewis and William Clark began an expedition across the newly acquired Louisiana Purchase territory in the United States. For a little over two years, Lewis and Clark led their corps through some 8,000 mi (12,800 km) of unexplored lands, acquiring scientific samples and creating maps.

1826–63

Johan Heinrich von Thunen, an important theorist in the science of land use, publishes his works, bringing together the fields of economics and geography to provide an illustration of the balance between land cost and transportation costs. Although his system was designed to calculate optimal land distribution in preindustrialized Europe—before the development of railroads, for example—the equations and principles he developed remain the foundation of much of land management practices today, particularly in the developing world.

1844

In Germany, Alexander von Humboldt, Carl Ritter, and Friedrich Ratzel made substantial contributions to human and physical geography. Humboldt's publication Kosmos (1844) examines the geology and physical geography of the Earth. This work is considered by many academics to be a milestone contribution to geographic scholarship.

1848

Karl Marx and Friedrich Engels publish the Communist Manifesto. The relationship between the middle and working classes, and Marx's views on their association, has been greatly influential in wider social and political thought.

1853

U.S. Commodore Matthew C. Perry ended Japan's isolation when he steamed into Tokyo Bay.

1853

A survey drew the boundary between the U.S. state of Texas and Mexico down the middle of the Rio Grande. The first of a series of disputes came in the wake of floods in 1864, which caused a change in the river's course that left a chunk of 630 acres (about 1 square mi or 1.6 square km) of land north of the river. Several other wanderings resulted in losses or gains of land for both countries in the ensuing years.

1855

A French regional wine-rating system was conceived for the Universal Exposition in Paris, when Bordeaux chateaux (“estates”) were ranked along a five-tiered system of crus (“growths”). These commercially driven designations later extended to other locales, ultimately coexisting with official French labeling requirements and ratings and marking the advent of the discipline of wine geography.

1859

Charles Darwin publishes Origin of Species (1859) and suggests that natural selection determined which individuals would pass on their genetic traits to future generations.

1864

One of the earliest statements of environmental ideas came from George Perkins Marsh in his book Man in Nature or Physical Geography as Modified by Human Action. This book is often cited by scholars as the first significant academic contribution to conservation and environmentalism.

1880

The desire to find a shortcut from the Atlantic to the Pacific Ocean stretches back at least 500 years. The reality of construction on a canal began in 1880 when Ferdinand de Lesseps, who oversaw construction of the Suez Canal, gained a concession from the Colombian government, which ruled Panama, to begin work on the canal.

1882

The heads of the various railroads met in St. Louis, Missouri, and worked out a system by which they divided the United States into four standard time zones. Each zone would be centered on a meridian of longitude 15 degrees apart—15 degrees multiplied by 24 hour-wide zones producing the full 360-degree circle of the Earth.

1889

Hans Meyer, a German colonial geographer and rich heir of a huge Leipzig publishing house, first ascended Mt. Kilimanjaro's Kibo crater in 1889 and called it Kaiser-Wilhelm-Spitze (since 1962, Uhuru Peak).

1892

New York City's Ellis Island opened to handle the increasingly large volume of immigrants; in 1907 immigration reached its peak of more than 1.2 million people.

1898

Cuba became independent, and Puerto Rico fell under U.S. administration. The Spanish-American War ended 400 years of Spanish dominion in the Americas and marked the rise of the United States as a world power.

1908

In 1908, U.S. scientist Frank B. Taylor invoked the notion of continental collision to explain the formation of some of the world's mountain ranges.

1911

The environmental determinist movement started with the publication of Ellen Churchill Semple's book (The Influences of the Geographic Environment), in which she explained how the environment is considered as a major factor in the location of human settlements and economic activity.

1912

William Davis, among the leading geographers of the early part of the 20th century, retired from Harvard University. Today, Davis might be more narrowly considered a geomorphologist based on his major research interests. But in his time, Davis enjoyed considerable influence over the direction and conduct of geographical science in the United States and in Europe.

1914

With the outbreak of World War I, the Ottoman Empire lined up with the Central Powers and faced a humiliating defeat. After World War I ended in 1918, the empire was under the occupation of several Allied powers, including Britain and Greece. It was not until the Kemalist nationalist movement, named after its leader Mustafa Kemal, famously known as Kemal Ataturk (1881–1938), which ended the foreign occupation of Turkey in 1922, that the Ottoman Empire saw its demise. With the creation of Turkey in 1923, the oldest imperial power in the world was finally abolished and replaced by a secular republic.

1917

British troops took control of Jerusalem and established the British Mandate in Palestine. In 1949, with the end of the British Mandate, Jerusalem was divided into the New City, the capital of the new state of Israel, and the Old City, under Jordanian control. Jerusalem was unified under Israeli control after the Six Day War in 1967. Palestinians hope to see East Jerusalem as the capital of a Palestinian state. As part of the Oslo Accords in 1993, the fate of East Jerusalem was to be resolved by the Israelis and the Palestinians. However, renewed violence in 2000 has prevented such a settlement.

1917

The ecological niche concept is originated as an attempt to describe the general role of species in the community and to differentiate population, community, and ecological systems. The concept and term was introduced by J. Grinnell, who interpreted it in spatial sense as the ultimate distributional unit of a species. Later C. Elton (1927) concentrated mainly on niche functional aspects when describing an organism's place in its biotic environment in connection with its nutrition and other species.

1920s

A strong rejection of environmental determinism in American geography was led by Carl O. Sauer in the 1920s. For Sauer, the primary purpose of geography should be chorology—or the study of areas. Rather than constrain geographers within the limits of environmental influences, geography should study places in terms of regular characteristics that tied them together.

1929

The environment of the Earth can be broadly divided into four major systems: the atmosphere, hydrosphere, lithosphere, and biosphere. Russian scientist Vladimir Vernadsky coined the term biosphere in 1929.

1930s

A number of geographers with political as well as academic interests made political geography an instrument of nationalism. Notable among them were Rudolf Kjellen, a Swede, and Karl Haushofer, a German who was close to Rudolf Hess, Adolf Hitler's deputy in the 1930s. They developed a school of realpolitik and geopolitik, whose writings were used to give an intellectual rationale to 1930s German expansionism—not only the desire to occupy adjacent territories with substantial German populations, such as Austria and Sudetenland, but also Russian areas further east. Another geographer and politician, Sir Halford Mackinder, whose classic paper related state power to location, led parallel developments in the United Kingdom. In an era when movement of heavy goods and large armies was easier by sea than by land, maritime countries would dominate politically, but as land transport was becoming easier, so land-based powers were becoming stronger.
Mackinder argued that whoever controlled the “world island” (the heartland of Euro-Asia) should be able to control the globe—a geopolitical notion that influenced much strategic thinking throughout the century, until air power (and then power in space) came to dominate military strategy.

1933

Market geography is a subfield of economic geography, which focuses on the spatial nature of market forces. It derives its rationale from the central place theory, first argued in 1933 by German economic geographer Walter Christaller in his book on central places in southern Germany.

1937

Alexander L. Du Toit, a South African geologist, suggested two primordial continents: Laurasia in the north and Gondwanaland (or Gondwana) in the south.

1939–45

World War II marked the first time there was a truly global conflict or war, including Europe, the Americas, Africa, and Asia.

1939

The turn to the study of geographic regions gives birth to the areal differentiation movement in the mid-1930s with Richard Hartshorne's publication of The Nature of Geography.

1947–56

The Dead Sea (the lowest dry point on Earth at 1,292 ft below sea level or -395 m) became famous for the Dead Sea Scrolls, found in eleven caves in nearby Qumran from 1947 to 1956. Literally thousands of Biblical fragments and ancient Jewish documents were found, which added greatly to the understanding of these religions. Today, the shores of the Dead Sea contain popular beaches, resorts, and spas.

1948

A young meteorological theoretician, Jule Charney, succeeded in deriving simplified mathematical models of the atmosphere's motions, based on earlier work. The results were dramatic: air flow patterns over North America were accurately forecast 24 hours in advance with greater skill than ever before.

1950s–60s

With few exceptions, the elite—aristocrats, government officials, clergy, and the wealthy—lived in the center of ancient cities, which were usually located near the most important temples. Farther out were the poor, who sometimes huddled along the city walls together. However, the situation reversed in the 20th century, when rings of rich suburbs surrounded most cities and only the poor were left in the city centers. In the United States, the affluent and the middle class who abandoned inner cities populated the suburbs, which grew up around cities in the 1950s and 1960s.

1950

Starting in about 1950, geographic research experienced a shift in methodology. Geographers began adopting a more scientific approach that relied on quantitative techniques. The quantitative revolution was also associated with a change in the way in which geographers studied the Earth and its phenomena.

1952

The European Coal and Steel Community (ECSC) was founded by Germany, France, Italy, the Netherlands, Luxembourg, and Belgium, becoming the predecessor organization to the European Union (EU). The EU included 25 countries by 2004, with many of them adopting the common currency, the euro, to facilitate regional trade and commerce.

1953

The world's tallest peak, Mt. Everest (29,028 ft or 8,848 m) was climbed by Sir Edmund Hillary and Tenzing Norgay.

1954

The U.S. secretaries of commerce and defense adopted the nautical mile as a means of measurement. It is used in maritime and aerial navigation, in relation to how boat speeds and wind velocities are measured (one knot is one nautical-mile-per-hour). A nautical mile is approximately one minute of latitude and it used to express distance.

1957

Historian Karl Wittfogel published his book, Oriental Despotism, which introduced the concept of water control (hydraulic civilizations) as the basis for the rise and development of civilizations and despotic political systems, from Egypt to China.

1957

The Soviet Union launched the first successful orbiting space capsule, marking the beginning of human use of space for exploration. This led to detailed mapping and monitoring of the Earth's surface, as well as more accurate navigation using global positioning satellites 1960s Several American scientists, among them Jack E. Oliver and Bryan L. Isacks, integrated the notion of seafloor spreading with that of drifting continents and formulated the basis for plate tectonic theory.

1960s

The widespread introduction of the jet airplane for passenger travel reduced the time needed to reach even the most remote part of the globe. It resulted in massive expansion of business travel and new geographic linkages. Time and distance began to diminish in terms of interaction between once distant places.

1960s–70s

With the advent of the environmental movement in the 1960s, and the subsequent oil crisis and surging energy cost, energy studies became increasingly popular in the 1970s in geography as well as in the general research community.

1960s–70s

This period marked the beginning of the computer age and digital information revolution. Computers and the internet connected the world, regardless of time, distance, or culture: the first example of a global “village.”

1970s

A revival of interests in political geography from the 1970s onward was initially linked to the “quantitative revolution,” which the wider discipline experienced in the 1960s and 1970s. Work on electoral geography started then and geographers increasingly brought their spatial perspective to bear on a range of subjects broadly defined as “political” and relating in some ways to the operation of the state. Location and conflict (over land uses, public goods, and so forth) became topics considered by political geographers.

1979

The First World Climate Conference made climate change, or global warming, an international issue as it called on all governments to anticipate and prevent human alterations in climate.

1980s

The first commercial geographic information systems (GIS) are developed that relate spatial information to assets, phenomena, or events. A GIS is computerized, and, therefore, is a structured and integrated arrangement of computer hardware, software, and operating procedures and principles designed to support the management of spatial and nonspatial data. These data are collected often via satellite coordinates referenced to the Earth and are maintained in a database.

1983

In The Fractal Geometry of Nature (1983), Benoit Mandelbrot writes, “Clouds are not spheres, mountains are not cones, coastlines are not circles, and bark is not smooth.” In an effort to more properly analyze and represent nature mathematically, Mandelbrot developed a new geometric pattern called a fractal.

1995

Again in the news as an international issue, the location of the International Date Line has posed a navigation and time problem since at least the 1700s. In 1995, the line had a minor adjustment so that the new country of Kiribati would be entirely on the same side and the same day, and be the first to mark the new millennium.

1990s

The internet together with a new generation of related computer software and hardware produced a revolution in how we conceptualized and interacted with geographic places and spaces. This revolution was sustained by the continual diffusion of information and communication technology (ICT) into many segments of a globally connected society. These ICT forms include immersive multimedia, video conferencing, computer-aided design, electronic surveillance, consumer profiling, and virtual realities. Virtual geography refers to the creation of artificial geographies for communication and interaction purposes using concepts from the field of virtual reality (VR).

1991

In August, as Soviet leader Mikhail Gorbachev and his family were vacationing in the Crimea, a cabal of hardliners staged a coup and held Gorbachev under house arrest. The coup failed because the military refused to carry out the coup leaders' orders. Events continued to spiral out of control as the constituent republics of the Soviet Union clamored for more autonomy and, in the case of the Baltic republics, independence. After an impasse on the relationship between Moscow and the republics, the Soviet Union ceased to exist on December 25, 1991.

1993

The United States, Canada, and Mexico signed the North American Free Trade Agreement (NAFTA), which created a regional free trade zone that lowered tariffs and trading restrictions. NAFTA encouraged greater opportunities for cross-border investments and movement of goods and services among the three countries. The agreement went into effect in 1994.

1996

The Association of American Geographers acknowledged military geography as a subfield of geography and defined it as the application of geographic information, tools, and techniques to solve military problems in peacetime or war. The consideration of terrain, culture, politics, and economics in the pursuit of warfare remains a dynamic field of geographic study and a practical area of military application.

1997

More than 150 nations signed the first legally binding treaty, the Kyoto Protocol, aimed at cutting emissions of the main greenhouse gases believed to contribute to global warming. Later, the United States, under President George W. Bush, declined to participate in the protocol.

1997–98

The El Nino of 1997–98 was one of the worst in recent memory. The weather system caused vast fires in Indonesia and large economic losses impacted many areas, such as Australia and Southeast Asia, where drought occurred. Ironically, this El Nino came with much advance warning, and heavily populated areas like California were able to invest millions of dollars in preparation, thus avoiding more losses. Groups such as the National Oceanic and Atmospheric Administration (NOAA) predict and track El Ninos using satellites, research ships, buoy arrays, computer modeling, and other tools to analyze ocean temperatures, wind speeds, fish populations, precipitation, and other early indicators of developing weather systems.

2001

The terrorist attacks of September 2001 leveled New York City's landmark World Trade Center towers and killed more than 2,700 people. This was the start of an aggressive U.S. strategy to fight al-Qaeda and other terrorists on a global basis.

2004

Russia ratifies the Kyoto Protocol, the United Nations convention on climate change, which sets limits for the emission of greenhouse gases that contribute to global warming. The United States declines to sign the agreement, citing unfair quota levels for emissions from developed and developing countries.

2016

James Alcock, a professor at Pennsylvania State University, has estimated that at the current rate of destruction, the point of no return in the Amazon rainforest could be reached as early as 2016. Unchecked destruction could entirely wipe out the rainforest by the middle of the 21st century.

2050

It is speculated that one result of the continuing population explosion will be the creation of megalopolises, concentrations of urban centers that may extend scores of miles. It is thought that the first such growth could occur on the East Coast of the United States, where there may eventually be a single urban agglomeration stretching from Boston to Washington, D.C. Other emerging megalopolises include the Tokyo-Osaka-Kyoto complex in Japan, the region between London and the Midland cities in Great Britain, and the Netherlands-central Belgian area.