Though it is second in size to the Pacific, the Atlantic Ocean drains more of the Earth's land area than any other ocean. It was named by the ancient Greeks for Atlas, the character in their mythology who stood on pillars in the ocean to hold up the heavens. The Atlantic Ocean is bounded by the continents of Europe and Africa to the east and by North America and South America to the west. It extends from the Arctic Ocean in the north to Antarctica in the south. The equator divides the ocean into the North Atlantic and the South Atlantic. The South Atlantic is bigger than the North Atlantic. However, the North Atlantic has many large seas on its margins. Among these seas are the Gulf of Mexico, near North America; the Caribbean Sea, near Central and South America; and the Mediterranean Sea, the Black Sea, the Baltic Sea, and the North Sea and English Channel, all near Europe. Physical featuresThe surface area of the Atlantic, at about 31,830,000 square miles (82,440,000 square kilometers), is roughly half that of the Pacific Ocean. Its deepest point, at 27,493 feet (8,380 meters), is the bottom of the Puerto Rico Trench, north of the island of Puerto Rico. Scientists believe that the Atlantic Ocean was formed about 180 million years ago. At that time there was only one continent on Earth. This giant ancient continent, called Pangaea, began to split apart, separating the Americas from Europe and Africa and forming the Atlantic. Even now, the ocean is getting wider at the rate of up to 4 inches (10 centimeters) per year. A world map shows that the present-day continents “fit together” across the Atlantic. Undersea featuresBeneath the middle of the Atlantic is an immensely long undersea mountain range called the Mid-Atlantic Ridge. In some places the Mid-Atlantic Ridge reaches above sea level and forms islands. Deep undersea plains lie on both sides of the Mid-Atlantic Ridge. The plains are flat, because layers of debris from living creatures, gravel, and clay have settled there over millions of years. Volcanoes have risen from these plains in certain places to form undersea mountains and islands. Bordering the plains are the shelves from which the continents rise. IslandsCertain islands in the Atlantic are called oceanic, because they rise directly from the plains of the ocean floor. Most oceanic islands were formed from volcanoes. Examples are the Cape Verde Islands near Africa and Bermuda, which is closest to North America. Iceland is a volcanic island that rises from the Mid-Atlantic Ridge. Other islands are called continental islands because they are based on the same undersea shelf that supports a nearby continent. The British Isles are continental islands that have an underwater connection with Europe. In the same way, Newfoundland is connected to North America and the Falkland Islands to South America. Currents and climateThe waters of the ocean move in patterns called currents. Currents carry heat and influence climate. The most outstanding example is the Gulf Stream, which flows from southern North America to Europe. Because of the Gulf Stream, Western Europe is much warmer than the region of eastern North America that lies due west of it. That region of North America is affected by the Labrador Current, a cold current from the north. In general, the main currents of the Atlantic Ocean move in a clockwise direction in the Northern Hemisphere and a counterclockwise direction in the Southern Hemisphere. This means that currents move from east to west near the equator and from west to east in the Northern and Southern hemispheres. In the middle of the North Atlantic is the Sargasso Sea, a large, relatively still region of floating seaweed. Heat and water vapor sometimes combine to create large circular tropical storms. In the Atlantic, these storms are called hurricanes. The Caribbean region and southeastern North America are especially prone to hurricanes. Hurricanes can be destructive to coastal areas but lose their force quickly over land. One of the most visible features of the ocean in relation to the coasts is its tides. The pull of gravity from the moon affects the water level of the ocean at the coasts every day. This is most noticeable in the Bay of Fundy, between New Brunswick and Nova Scotia in Canada. The difference between high and low water there can be as much as 40 feet (12 meters). EconomyThe Atlantic produces much of the world's total catch of fish. Most are taken in continental shelf areas. For centuries, the Grand Banks area near Newfoundland in Canada was one of the world's richest fishing grounds. By the 20th century the numbers of fish there had declined drastically because of overfishing. However, a conservation program helped revive the fishing industries. Hake and herring are caught in both the North and the South Atlantic. Cod is found in the north, and tuna in the south. Warm coastal areas provide shrimp and other shellfish. The ocean is also a source of many minerals. Large deposits of petroleum, natural gas, and coal are found in the Atlantic. Fields of petroleum and natural gas lie in the North Sea, Gulf of Mexico, and Caribbean, and off the coasts of west-central Africa, Brazil, Canada, Argentina, and the United States. Tin and coal are mined under the ocean floor off Great Britain. Large diamond deposits are found along the southwestern coast of Africa. Sand, gravel, and shell deposits are mined off the coasts of the United States and Britain. Deposits of shells that have calcium content are dredged off the coast of Iceland and the Bahamas and used to manufacture cement. Salt and bromine are extracted from seawater. Sulfur is recovered from the floor of the Gulf of Mexico. Many cargo ships use the ocean as a trade route. The Atlantic is also a playground for boaters, windsurfers, sport fishers, cruise ship passengers, and whale watchers. The economies of many coastal areas depend on recreational industries. ExplorationThe ancient Egyptians, Celts, Phoenicians, and Romans sailed on the Atlantic Ocean, but it is not known exactly how far west their wanderings took them. In about 1000 AD, Viking seafarers from Northern Europe probably reached the island of Newfoundland, off the coast of North America, but their settlements were not permanent. Several hundred years later, Europeans began a new era of discovery and settlement that lasted more than 200 years. The Portuguese discovered the Azores and Madeira and sailed along the western coast of Africa in the first half of the 15th century. In 1492, Christopher Columbus made his famous first voyage across the Atlantic in search of a new trading route to the Far East. At about the same time, Portuguese seafarers led by Bartolomeu Dias mapped the entire western coast of Africa. In 1520, Ferdinand Magellan sailed around South America and discovered the strait, now named after him, that links the Atlantic and Pacific oceans. Serious scientific efforts to study the Atlantic began during the 1800s. The American naval officer Matthew Fontaine Maury charted the winds, the currents, and the floor of the Atlantic in the 1840s and 1850s. Surveys of the ocean paved the way for the first telegraph cable to be laid across the ocean floor. The cable, which was laid in 1866, improved communication between Europe and the United States. More recently, remote sensing by satellites in outer space has allowed researchers to measure temperature patterns across the Atlantic. Modern underwater equipment has taken investigators down 13,000 feet (4,000 meters) to the wreck of the Titanic, a passenger ship that sank in 1912 after hitting an iceberg. Environmental issuesSome areas of the Atlantic Ocean have become heavily polluted as a result of human activity. Most pollution is land-based. This includes sewage from cities, industrial waste from factories, and fertilizers and pesticides from farms. Oil spills from ships or offshore wells are another pollution source. Sometimes, harmful ocean algae build up in coastal waters, causing a problem known as red tide or black water. Overfishing of the Atlantic is another environmental issue of great importance. The Grand Banks of Newfoundland, once thought to hold more fish than could ever be caught, were nearly emptied in the 1990s. Tuna and pilchard populations in the South Atlantic were also reduced. Some countries have set limits on how many fish can be caught in certain areas. They have also set up programs to protect the fish that are left and to rebuild the fish populations. |