The Handy Geography Answer Book. Paul A Tucci

Geographic thought has been present for thousands of years. Maps drawn in the sand, etched in stone, or painted on the walls of caves, as well as explorations to distant lands, were made by the earliest civilizations. Geographic knowledge has been accumulating since the beginning of humankind.

      What new epoch has recently been proposed by Nobel Prize winner Paul Crutzen?

      Most epochs last approximately more than 3 million years, enough time to deposit traces of subtle changes in the conditions on the planet, for scientists to discover in future years. Dutch atmospheric chemist and Nobel Prize winner Paul Crutzen coined the term “Anthropocene,” or “New Man,” epoch because changes to our planet, brought on by human activities like habitat destruction, environmental degradation, and the extinction of thousands of plant and animal species since the beginning of the Industrial Revolution two hundred years ago, will leave an indelible mark in the boundary layer of the surface of our planet. But some scientists disagree and assert that it really is not a new epoch, just a warm period during our current Holocene Epoch, or Ice Age, which should continue for another million years.

      What is the AAG?

      The Association of American Geographers (AAG) is a professional organization of academic geographers and geography students. The AAG was founded in 1904 and publishes two key academic journals in geography, the Annals of the Association of American Geographers and the Professional Geographer, as well as the AAG Review of Books and the online AAG Newsletter. The AAG also holds annual conferences and supports regional and specialty groups of geographers. Its membership spans more than sixty countries.

      What is the NCGE?

      The National Council for Geographic Education (NCGE) is an organization of educators that seeks to promote geographic education. The NCGE was founded by educator George Miller and was chartered in 1915 with a stated mission to enhance the status and quality of geography teaching from kindergarten through university. The NCGE publishes the Journal of Geography and holds conferences every year.

      What is the National Geographic Society?

      Founded in 1888, the National Geographic Society is one of the largest scientific and educational institutions in the world. It has supported exploration, cartography, and discovery, and it publishes the popular magazine National Geographic, in English and many other languages, and is the fifth-most-popular magazine in the United States. The society’s publishing operations reach a global audience of over 600 million people each month.

      What do modern geographers do?

      While there are a few jobs with the title of “geographer,” many geography students use their analytical ability and knowledge of the world to work in a variety of fields. Geography students often take jobs in fields such as city planning, cartography, marketing, real estate, environment, and teaching.

      The geologic time scale

THE EARTH

      How old is the Earth?

      The Earth is approximately 4.54 billion years old (+/- 1%). We know this because scientists use radiometric dating techniques to analyze samples in order to determine its age. One of the oldest materials found in the Earth is a sample of crystals of the mineral zircon, found in Western Australia, that is at least 4.04 billion years old.

      How was the Earth formed?

      Scientists believe that the Earth was formed, along with the rest of the solar system, from a massive gas cloud. As the cloud solidified, it formed the solid masses such as the Earth and the other planets.

      What is the circumference of the Earth?

      The circumference of the Earth at the equator is 24,901.55 miles (40,066.59 km). Due to the irregular, ellipsoid shape of the Earth, a line of longitude wrapped around the Earth going through the north and south poles is 24,859.82 miles (40,000 km). Therefore, the Earth is a little bit (about 41 miles [66 km]) wider than it is high. The diameter of the Earth is 7,926.41 miles (12,753.59 km).

      Is the Earth a perfect sphere?

      No, the Earth is a bit wider than it is “high.” The shape is often called a geoid (Earth-like) or an ellipsoid. The rotation of the Earth causes a slight bulge toward the equator. The circumference of the Earth at the equator is 24,901.55 miles (40,066.59 km), which is about 41 miles (66 km) greater than the circumference through the poles (24,859.82 miles [40,000 km]). If you were standing on the moon, looking back home, it would be virtually impossible to see the bulge, and the Earth would appear to be a perfect sphere (which it practically is).

      What is a hemisphere?

      A hemisphere is half of the Earth. The Earth can actually be divided into hemispheres in two ways: by the equator and by the Prime Meridian (through Greenwich, England) at 0 degrees longitude and another meridian at 180 degrees longitude (near the location of the International Date Line in the western Pacific Ocean. Zero and 180 degrees longitude divide the Earth into the Eastern (most of Europe, Africa, Australia, and Asia) and Western (the Americas) Hemispheres.

      What is the equator?

      The equator divides the Earth into Northern and Southern Hemispheres. There are seasonal differences between the Northern and Southern Hemispheres. When it is winter in the Northern Hemisphere, it is summer in the Southern Hemisphere. But there is no such difference between the Eastern and Western Hemispheres.

      Western (left) and Eastern Hemispheres of our planet

       How was the circumference of the Earth determined?

      The Greek geographer and librarian at the Great Library of Alexandria, Eratosthenes (c. 273—c. 192 B.C.E.), was aware that the sun reached the bottom of a well in Egypt only once a year, on the first day of summer. The well that he studied was near the city of Aswan and the Tropic of Cancer (where the sun is directly overhead at noon on the summer solstice). Around the year 240 B.C.E., Eratosthenes estimated the distance between the well and the city of Alexandria based on the length of time it took camel caravans to travel between the two places. He measured the angle of the sun’s shadow in Alexandria at the same time that the well was lit by the sun and then used a mathematic formula to determine that the circumference of the Earth was 25,000 miles (about 40,000 km)—amazingly close to the actual figure, which at the equator is 24,898 miles (40,070 km).

      What are the Arctic and Antarctic Circles?

      The circles are imaginary lines that surround the North and South Poles at 66.5 degrees latitude. The Arctic Circle is a line of latitude at 66.5 degrees north of the equator, and the Antarctic Circle is a line of latitude at 66.5 degrees south. Areas north of the Arctic Circle are dark for 24 hours near December 21 and areas south of the Antarctic Circle are dark for 24 hours near June 21. Almost all of the continent of Antarctica is located to the south of the Antarctic Circle.

      If the Earth is so large, why did Christopher Columbus think that India was close enough to reach by sailing west from Europe?

      The Greek geographer Posidonius did not believe Eratosthenes’s earlier calculation, so he performed his own measurement of the Earth’s circumference and arrived at the figure of 18,000 miles (28,962 km). Columbus used the circumference estimated by Posidonius when he argued his plan before the Spanish court. The 7,000-mile (11,263-km) difference between the actual circumference and the one Columbus used led him to believe he could reach India rather quickly by sailing west from Europe.

      How fast does the Earth spin?

      It depends on where you are on the planet. If you were standing on the North Pole or close to it, you would be moving at a very slow rate of speed—nearly zero miles per hour. On the other hand, those who live at the equator (and therefore have to move about 24,900 miles [40,000 km] in a 24-hour period) zoom