The Handy Geography Answer Book. Paul A Tucci

in the mid-latitudes, as in the United States, breeze along from about 700 to 900 miles (1,126 to 1,448 km) per hour.

      Why don’t we feel the Earth moving?

      Even though we constantly move at a high rate of speed, we don’t feel it, just as we don’t feel the speed at which we’re flying in an airplane or driving in a car. It’s only when there is a sudden change in speed that we notice, and if the Earth made such a change we would certainly feel it.

      Does the Earth spin at a constant rate?

      The rotation of the Earth actually has slight variations. Motion and activity within the Earth, such as friction due to tides, wind, and other forces, change the speed of the planet’s rotation a little. These changes only amount to milliseconds over hundreds of years but do cause people who keep exact time to make corrections every few years.

      What is the axis of the Earth?

      The axis is the imaginary line that passes through the North and South Poles about which the Earth revolves. Because the Earth is tilted along this spin axis, as we make our way around the sun in an elliptical orbit for 365 days, we have our seasons (winter, spring, summer, and fall). As the Earth’s axis is pointed toward the sun for people in the Northern Hemisphere, we experience summer. At the same time, for people in the Southern Hemisphere, as the axis points away from the sun, we experience winter.

      What is inside the Earth?

      The Earth is comprised of several layers: crust, mantle, and core. The outermost part of the Earth, the crust, is divided into huge plates that float atop the mantle, and are always in motion. The crust is comprised of the elements iron, oxygen, silicon, magnesium, sulphur, nickel, and trace amounts of many other elements. Beneath the crust is the mantle, which is about 1,800 miles (2,890 km) deep and is composed of silicate rocks, which are heated and cooled by the core. The mantle, which makes up the bulk of the interior of the Earth, is composed of three layers—two outer layers are solid and the inner layer (the asthenosphere) is a layer of rock that is easily moved and shaped. At the very center of the Earth is a dense and solid inner core of iron and other minerals that is about 1,520 miles (1,220 km) wide. Surrounding the inner core is a liquid (molten) outer core that is about 1,355 miles (2,180 km) thick.

      If I dug through the Earth, would I end up in China?

      If you are in North America and you were able to dig through the Earth (which is impossible due to such things as pressure, the molten outer core, and solid inner core), you would end up in the Indian Ocean, far from landmasses. If you were really lucky, you might end up on a tiny island, but you’re surely not going to end up in China. The points at opposite sides of the Earth are called antipodes. Most antipodes of Europe fall into the Pacific Ocean.

      When do earthquakes occur?

      Earthquakes occur when the plates that comprise the Earth’s crust rub against each other. We have mountains created when these gigantic plates collide and large trenches created when one plate slides underneath another.

      What is the Mid-Atlantic Ridge?

      We don’t get to appreciate the beauty of this huge mountain range because it’s located at the bottom of the Atlantic Ocean (with one exception: Iceland is a part of the ridge). It is part of one of the longest mountain ranges in the world. The ridge is a crack between tectonic plates where new ocean floor is being created as magma flows up from under the Earth. As more crust is created, it pushes the older crust farther away. The new crust at the ridge piles up to form mountains and then begins to move across the bottom of the ocean. Because the Earth can’t get larger as more crust is created, the crust eventually has nowhere to go except back into the Earth. This is where subduction occurs.

      What is subduction?

      When two tectonic plates meet and collide, crust must either be lifted up, as in the case of the Himalayas, or it must be sent back into the Earth. When crust from one plate slides under the crust of another, it is called subduction, and the area around the subduction is called a subduction zone.

      In Iceland’s National Park of Thingvellir one can visit the rift valley that is part of the Mid-Atlantic Ridge.

      What is the North Magnetic Pole?

      The North Magnetic Pole is where compass needles around the world point. Today it is located beyond Canada’s Northwest Territories near 85.9 degrees north, 147 degrees west (latitude and longitude), about 900 miles (1,450 km) away from absolute North Pole. Since it moves continuously at about 34 miles per hour (55 km per hour), global research scientists are constantly trying to determine the current location of the pole. In order to determine true north, look at a recent topographic map for your local area. It should note the “magnetic declination,” which means the degrees east or west that you’ll need to rotate your compass to determine which way is actually north.

      Who had the first idea that there was a magnetic North Pole?

      As early as the year 1600, English physician and naturalist William Gilbert was the first person to define the North Magnetic Pole as the point on the Earth where the Earth’s magnetic fields point vertically downward. It was not until 1831 that James Clark Ross found this point. Another famous explorer, Roald Amundsen, found the North Magnetic Pole in 1903, but in a different location. In a third major exploration in 1947, Paul Serson and Jack Clark found the pole on Prince of Wales Island.

CONTINENTS AND ISLANDS

      What are continents?

      Continents are the six or seven large landmasses on the planet. If you count seven continents, these include Europe, Asia, Africa, Australia, Antarctica, North America, and South America. Some geographers refer to six continents by combining Europe and Asia as Eurasia, due to the fact that it is one large tectonic plate and landmass. So whether you count Europe and Asia as one continent or two (divided at the Ural Mountains in western Russia) is up to the individual. Australia is the only continent that is its own country.

      Why is the number of continents controversial?

      We find that there is controversy about how many continents there truly are because of how experts classify and define the word “continent.” It is generally accepted that a continent is a very large, continuous, and discrete landmass, likely separated by water. By using this definition, places like Greenland should be classified as a continent (since, like Australia, it is a landmass surrounded by water), but it is not. North and South America are typically classified as two continents, even though they are joined. Often, experts classify Europe and Asia as two continents, even though they are joined together, with no water between them. Depending on where you live on this planet, you may conclude that there are 6 or 7 continents. In most of the English- and Chinese-speaking world, there are seven continents (Asia, Africa, Europe, North America, South America, Australia, and Antarctica), while in Russia, Eastern Europe, and Japan, experts there consider Europe and Asia as one continent called Eurasia. And, in other parts of the world, experts consider North and South America as one landmass. So according to these two latter views of geography, we only have 6 continents, and not seven.

      The crust of our planet is a network of several tectonic (or lithospheric) plates, ranging from just a few hundred miles across to thousands of miles, such as the Pacific and Antarctic plates.

      What is the largest continent?

      If you were to combine the two landmasses of Europe and Asia into one, the largest continent is Eurasia at 21,100,000 square miles (54,649,000 square km). But even if you consider Europe and Asia to be two separate continents, Asia is still the largest, at 17,300,000 square miles (44,807,000 square km).

      What is a subcontinent?

      A subcontinent is a landmass that has its own continental shelf and its own continental plate. Currently, India and its