The Handy Geography Answer Book. Paul A Tucci

potential intersection with Earth’s orbital path to determine if they are a threat.

       WATER AND ICE

      How much of the Earth is covered by water?

      About 71% of the surface area of the Earth is covered by water. Oceans hold 96.5% of the Earth’s water. The other 29% of the Earth is land, located primarily in the Northern Hemisphere. If you look at a globe, you’ll notice that the Southern Hemisphere has a much larger surface area covered with water.

      How much is the sea level rising?

      Scientists believe that sea levels are rising by approximately .12 inches (3.05 mm) per year. The rising sea levels have been more extreme during the past century because of the increase in temperature of the world’s oceans as well as the gradual melting of ice in the Earth’s polar regions. The recent increase in sea levels are more extreme than over the past one thousand years.

      What countries are threatened the most from rising sea levels and may cease to exist in the twenty-first century?

      Many of the world’s small island nations are concerned about the rising sea levels. Lowlying island nations of the Pacific and Indian oceans are most at risk, most notably Tuvalu, the Maldives, Palau, and Micronesia. Other candidates for severe flooding and reclamation of coastal land by the impending sea include Bangladesh, India, Thailand, Vietnam, Indonesia, and China, affecting the lives of hundreds of millions of people.

      How much land disappears when the sea level rises?

      Scientists believe that as the seawater rises by 0.04 inches (1 millimeter), the shoreline disappears by 4.9 feet (1.5 meters). This means that if the sea level rises by 3.28 feet (1 meter), the shorelines will extend another 1 mile (1.6 km) inland.

       What is a nautical mile?

      Used for measuring ocean-based distances, a nautical mile is equivalent to approximately 6,076 feet (1,852 meters) or 1.15 miles (1.85 km). The speed of ships is measured in knots. One knot is equivalent to one nautical mile per hour.

      What is the average depth of the Earth’s oceans?

      The average depth of the Earth’s oceans is approximately 14,000 feet (4,267.2 meters) deep.

      What percentage of the Earth’s surface is covered by water?

      Approximately 70.8% of the Earth’s surface is covered by saltwater. Although we have but one giant, interconnected ocean covering the planet, we divide it into large sections called oceans and smaller bodies of water called seas.

      How is water distributed on the Earth?

      The oceans contain approximately 97% of all of the world’s water. Of this ocean water, 96% is saltwater or saline. The other 4% is comprised of freshwater flows, ice, snow, and precipitation. Of the 3% of nonocean water, approximately 69% of that is frozen in the form of glaciers and ice caps; 90% of this water is in Antarctica, and about 9% is in Greenland. What remains is the source of most of the water that we use each day. Of this useful water, 30% is merely groundwater, and .3% of this water is actually found in rivers and lakes. So less than 1% of all available fresh water on the planet can be found in rivers and lakes. Only .1% of water is found in the atmosphere.

      What are the names of the oceans and seas?

      The five largest bodies of water are named the Atlantic Ocean, the Pacific Ocean, the Indian Ocean, the Arctic Ocean, and the Southern Ocean. Each of the world’s oceans have numerous seas, including the Baltic Sea, the Mediterranean Sea, the Greenland Sea, the Ross Sea, the Andaman Sea, and the Coral Sea.

      How many seas are landlocked and not connected to the world’s oceans?

      There are four seas that are completely surrounded by land: the Aral Sea, the Caspian Sea, the Dead Sea, and the Salton Sea.

      What is so dead about the Dead Sea?

      The Dead Sea was considered to be dead because of its high salinity (at 34.2%, which is approximately 9.6 times more salty than the world’s oceans). So aquatic life cannot survive in such conditions. But there are several other places that have more salinity than the Dead Sea, including Lake Vanda (Antarctica), Lake Assal (Djibouti), Lagoon Garabogazköl (Caspian Sea), and many lakes in the McMurdo Dry Valleys (Antarctica), where the salinity in each of them has been measured at more than 40%.

      What are trenches?

      Trenches are deep, “v”-shaped depressions on the Earth’s surface, lying in the deepest parts of the Earth’s oceans, mostly in the Pacific Ocean. They are caused by subduction, where tectonic plates collide, pushing one heavier, older plate underneath a relatively less dense, newer plate, causing the formation of deep trenches, mountains, earthquakes, and volcanic islands.

      The deepest point in the oceans of the planet is the Mariana Trench in the South Pacific Ocean. The above map also shows where the Challenger Deep is located, with a depth of 35,814 feet (10,916 meters).

       What island did Robinson Crusoe shipwreck on?

      Daniel Defoe based his novel Robinson Crusoe on the real-life story of Alexander Selkirk. Selkirk was an English sailor who had an argument with the captain of his ship and asked to go ashore on the island of Más a Tierra (also known as Robinson Crusoe Island or Isla Robinson Crusoe), about 400 miles (644 kilometers) west of Santiago, Chile, in the South Pacific Ocean. Selkirk was stranded on the island from 1704 to 1709, when he was rescued by another English ship.

      What are some of the deepest points in the oceans?

      Lying deep below the Pacific Ocean, about 200 miles (322 km) south of the island of Guam, is the Marianas Trench (also known as the Mariana Trench), which is 1,554 miles (2,550 km) long and 44 miles (71 km) wide. The deepest point of the Marianas Trench is named Challenger Deep at 35,814 feet (10,916 meters), first discovered by the HMS Challenger in 1875. In the Atlantic Ocean, the Puerto Rico Trench is 28,373 feet (8,648 meters) below the surface. In the Arctic Ocean, the Eurasia Basin at the Litke Deep is 17,881 feet (5,449 meters) deep. The Java Trench or Sunda Trench in the Indian Ocean is 25,344 feet (7,725 meters) deep. Another deep point of note in the Pacific Ocean is Monterey Canyon off the coast of northern California. It is about 95 miles (153 km) long and 11,800 feet (3,600 meters) deep. The cold waters generated in the trench create a perfect environment rich in foods that support a diverse range of wildlife.

      In comparison to all of these ocean canyons, the most famous land canyon—the Grand Canyon in Arizona—is 277 miles (446 km) long and 6,000 feet (1,829 meters) deep. The world’s ocean canyons are much more impressive, but most people will never see them.

      What is a sounding?

      A sounding is a method once used for determining the depth of the ocean by dropping a weighted line into the water and measuring the length of that line when it stops descending at certain predetermined points.

      Where is the farthest point from land?

      In the middle of the South Pacific Ocean lies the Pacific pole of inaccessibility, a spot on the Earth that is the farthest from any land. It is 1,670 miles (2,688 km) from any land. Located at 48°52.6′ South and 123°23.6′ West, this spot is approximately equidistant from Antarctica, Australia, and Pitcairn Island.

      Where is the farthest point from an ocean?

      The Eurasian pole of inaccessibility is located in Xinjiang Province, in northern China, and is over 1,600 miles (2,574 km) from any ocean. Located at 46°17′ North, 86°40′ East, the land is approximately equidistant from the Arctic Ocean, Indian Ocean, and Pacific Ocean.

      What is the world’s largest island?

      The world’s largest island is Greenland (in Greenlandic, Kalaallit Nunaat). Greenland is located