Many thousands of years ago, a man stood on a hill, looking down upon the scenery spread before him a hundred feet below. At the far right of his view the terrain was littered with large and small boulders, home to many snakes and lizards but also a good shelter during a stampede. Straight ahead was the vast plain of high grass, dotted with only a few trees and stretching all the way to the high mountains in the far distance. And to the left began a thick forest, which in turn led to a wide river that was home to much wildlife. It was all so easy to see from this vantage point, yet once the man descended the hill, he lost all sense of perspective. Once he set foot into the forest, it was hard to keep track of distance and direction. Once he walked upon the plain, it was difficult to see where he was going. If only he could preserve this image permanently, he thought; if only he could etch the geography that lay below onto something more dependable than his mind. Thus was born the first map.
What Is Geography?
The word geography is of Greek origin. It comes from the Greek words "geo," meaning earth, and "graphy," meaning writing or describing.
Geography is place. When you set foot outside, you are immediately confronted with geography. Look around. Notice the particular features of your neighborhood. You may live in the heart of a great city, surrounded on all sides by huge skyscrapers. Or perhaps you live in a rural area with nothing in sight except fields. No matter where you live, your geographical location undoubtedly has many unique features, both natural and man-made.
The natural features (or landforms) of your location — mountains, hills, plains, deserts, canyons, streams, rivers, lakes, oceans, peninsulas, and islands — are its most basic geographical elements. Topography, the details of the earth's surface features, is closely connected to where people live and how they live. Location and surface features determine climate, which in turn determines a number of other things: the number of people who can live there, the type of crops that can be grown, the types of animals that can live there, and natural resources that can be found.
In short, where in the world you live affects how you live.
So how did the geography of the world come to be? What forces have shaped it?
Each of the earth's physical features was formed in a unique way and at a unique time. Some of the earth's features were formed billions of years ago, some were formed only thousands of years ago, and still others were formed recently. Under a seemingly calm surface, the earth is very restless. Much of the change to the earth's topography has been due to movement of its crust, the surface layer. The earth's crust is not solid and continuous. It is broken into a dozen major pieces, called plates, that move and shift (called plate tectonics). These motions account for much of the geological unrest on earth, including mountain formation, earthquakes, and volcanic eruptions.
The continents as we know them today did not take their current form until fairly recently. One billion years ago, all the land on the earth was massed together in a giant supercontinent. Between 750 and 540 million years ago, it began to split into pieces that drifted apart. But around 470 million years ago, the plates' movements shifted, and some of the land masses began to drift back toward one another. By about 270 million years ago, these land masses collided to create a supercontinent known as Pangaea (from Greek, meaning "all earth" or "all lands"). But just 30 million or so years later, around the time when dinosaurs first began to appear, the plates began to shift again, and Pangaea began to separate once more. Over the years, the continents continued to slowly drift apart.
By the time the last of the dinosaurs became extinct, the continents still did not look quite the way they do today. Even now, continental drift is occurring. North America and Africa are still moving away from each other, causing the Atlantic Ocean to expand. Tectonic plates around the world are moving at a rate between one and six inches per year. It may not seem like much, but over time it adds up.
Crash, Rumble, and Crumble: Forces That Shape the Earth's Geography
The earth's moving plates are the force behind the creation of its major mountains. When plates collide, they cause huge masses of rock to be uplifted. The "young" Rocky Mountains were formed between 50 and 100 million years ago, while the "old" Alleghenies along the East Coast were shaped nearly 300 million years ago, uplifted when North America and Africa collided. The Himalayas, the highest mountains in the world, were formed about 55 million years ago when India collided with Asia. They have continued rising, very slowly, since then.
Besides creating mountains, the constant movement of the earth's plates causes other changes, notably earthquakes. Earthquakes occur along faults, the boundaries of two different plates. When the plates shift, either rubbing against each other or pulling apart, an earthquake can occur. The northward-moving Pacific Plate and the southward-moving North American Plate meet along California's San Andreas Fault, the location of the powerful 1906 San Francisco earthquake and the 1989 Loma Prieta earthquake.
Volcanoes are formed because of movement of the earth's plates. They are created when lava flows from the upper mantle (the molten layer below the crust) to the surface through cracks, often caused by tectonic movement along fault lines. The lava, volcanic ash, and cinder form a cone around the flow. Volcanic eruptions alter the features of the earth, including the height and shape of the volcanoes themselves. When Mount St. Helens erupted in May 1980, it literally blew its top, losing 1,300 feet of height. The eruption also turned more than 200 square miles of surrounding forest into a dead zone, with hot lava, ash, and mud destroying all living things in their path.
There are also other factors are at play in the shaping of our world. Weathering has a major long-term impact on the geological features of the earth. For example, geological evidence has shown that the ancient Allegheny mountain peaks, more than 200 million years older than the Rockies, may have originally towered 35,000 feet high. (The highest Rockies are around 14,000 feet tall.) The Allegheny Mountains have weathered over time, however, dramatically reducing their altitudes and creating a plateau effect — they are not the sharp, high peaks of mountain ranges such as the Rockies. The highest point in the Alleghenies is now 6,711 feet above sea level, and there are more than 40 peaks that reach over 6,000 feet in altitude.
Water erosion is another major factor in the creation of the earth's current geographical features. First, rainwater can slowly erode mountains and hills by carrying soil elsewhere. Eventually, the loss of soil can have a big impact. Major rainfall can cause mudslides and the collapse of whole sections of hills.
In addition, when rain reaches the earth's surface, it runs downhill in any direction that it can. The force of the running water will begin to create a slight channel effect, so that rainwater follows that course every time. With each rainfall, the water will cut the channel deeper and deeper until, after hundreds or thousands of years, it becomes deep enough to turn into a stream or river.
By itself, wind can also cause erosion and shifting, especially in open areas with sand (beaches) or dry, loose soil. Wind is also a major force in creating large waves, which can cause severe beach erosion.
Water can alter geography in other ways. During a hurricane or major storm, surging seas can wash away beaches and alter maps. A 1938 hurricane that hit New England submerged a swath of land along the south shore of Long Island, creating the Shinnecock Inlet, which exists to this day.
Glaciation, the growth and movement of glaciers, has been another factor in shaping geography. Over the last three million years, there have been four ice ages, periods when glaciers have advanced southward, covering much of the earth's northern latitudes. When they are stationary, glaciers do not cause any change to the earth's features. But their advance and retreat, or forming and melting, can cause major changes. The advance and retreat of glaciers during the last ice age (occurring between about 100,000 years ago and 10,000 years ago) made lasting changes to the Northern Hemisphere's features. They moved boulders, polished rocks, carved valleys, left hill-shaped deposits of glacial soils, and created numerous lakes and ponds. The Great Lakes were formed by glaciers and are the largest glacial lakes in the world. The famous Lake District in England was also formed by glaciers. Only a few small glacier pockets remain in the mountainous parts of the western United States.
Our Changing Understanding of Geography
Almost every creature on earth has a sense of geography, of place. Even the smallest animals are aware of their surroundings, and though they cannot describe it in words as we can, they know the difference between a forest and a meadow, a mountain and a valley, or a river and a desert. They know because their lives depend upon it. Whether bird, mammal, or reptile, a creature must know where to go for water, for shelter, for food, to mate, and to raise its young. Each of these activities may occur in a distinct geographical location within the animal's habitat.
People have always had a keen sense of geography. For as long as humans have been in existence, they have been on the move. In fact, evidence shows that some of our distant ancestors left Africa nearly two million years ago for Asia.
The first humanlike creatures to leave Africa did so 100,000 years ago, and they gradually spread to the rest of the world, reaching North America over the Bering Strait land bridge at least 15,000 years ago. Once they got to the New World, they made their way south and west, populating North America and then South America by 13,000 years ago.
Since humans traveled so widely, their knowledge of geography was essential. Each band of humans had to decide where best to settle. They clearly recognized the different geographical features they saw around them. In addition, they captured what they saw using pictures.
Though humans were probably making maps long before, one of the oldest maps ever discovered is a 25,000-year-old engraving of several local land features, scratched on a rock in the Pavlov region of the Czech Republic. Another ancient map, engraved on a rock in a cave in Navarra, Spain, is believed to be 14,000 years old. A map called the Mezherich map, dating to about 12,000 B.C., has been found in the Ukraine. These early maps are very crude by modern standards, but to the people who made them, they were the best representations of the world they saw around them.
As civilizations grew, so did people's knowledge of geography. Understanding their environment helped them build cities, develop agriculture, and raise livestock. Over time, maps became more sophisticated. The ancient Egyptians, for example, made maps of their roads on wooden tablets and papyrus. The Babylonians also had a detailed geographical understanding of their world and were making maps on clay tablets 4,300 years ago.
The Greeks made great contributions to geographical knowledge. Homer, the ninth-century-B.C. Greek author of the epic poems The Odyssey and The Iliad, was fascinated by the earth's geography. Homer believed the earth was a flat, circular disk. The Odyssey follows a soldier named Odysseus's ten-year journey from Troy to Ithaca. Along the way, Odysseus gets lost and travels to many strange lands and has many adventures.
Anaximander (born around 610 B.C.) was one of the pioneers of cartography, or mapmaking. He was believed to have produced a map of the world on a bronze tablet. The map was crude by today's standards but groundbreaking for its time. It showed the known world surrounded by ocean and used the same flat disk idea that Homer did. It was most accurate when showing the lands immediately surrounding the Mediterranean but less precise for lands farther from Greece.
Around the sixth century B.C., with advancements in mathematics and astronomy, ancient Greeks began to accept the idea of the earth as a sphere.
The more the early geographers traveled, the more they were able to detail in maps. The personal knowledge of Herodotus, who lived around 440 B.C., extended to Libya and Ethiopia to the south, India to the east, and Spain to the west. A fourth-century-B.c. Greek explorer named Pytheas sailed to Great Britain and traveled extensively there, further extending the Greeks' knowledge of the world. He even estimated Great Britain's perimeter based on measurements he took along the coast. Pytheas came up with a distance of about 5,000 miles. Though his estimate is far from the true perimeter of Britain (it has over 7,700 miles of coastline, including all the bays and inlets), he was able to provide some idea of the shape of the island.
Eratosthenes (276–194 B.C.) used observations about the sun's position in the sky at both Syrene and Alexandria, as well as the distance between the two places (5,000 stadia), to figure out that distance represented 1/50th of the earth's circumference. He then calculated the circumference to be 250,000 stadia — around 25,000 to 30,000 miles; we are not certain exactly how many stadia make up a modern mile — which is very close to the earth's actual circumference of 24,900 miles.
The Roman Empire carried on many of the traditions and scientific advances of the Greeks. Another great contributor to ancient geography and cartography was Ptolemy (c. A.D. 90–165), a Roman citizen living in Egypt. He was the author of a book called Geography, in which he described and gave coordinates for numerous places in Europe, Asia, and Africa. His map of the known world was more extensive and more accurate than any that had been done before.
Geography in the Middle Ages
Following the collapse of the Roman Empire in the fifth century A.D., scientific knowledge did not advance very much. The geographical progress that had been made by the Egyptians and Greeks over the centuries slowed. The idea of a spherical earth began to fall out of favor. Instead, people cited passages in the Bible that seemed to contradict the round earth theory.
One of those who pushed the idea of a flat earth was Cosmas Indicopleustes, a sixth-century Egyptian monk. Cosmas wrote a book called Christian Topography, which relied heavily on Bible passages to develop a theory of the earth's geography. According to Cosmas, the earth was a flat rectangle that was 400 days' journey in length and 200 days' journey in width. The land was surrounded on all sides by an ocean. Cosmas wrote in his prologue:
[I] exhort my readers to examine the sketch of the universe and the stellar motions which we have prepared as a representation of the organic sphere of the pagans ... [and] to overthrow from the foundation the error of the pagan theories.
The Deity accordingly having founded the earth, which is oblong, upon its own stability, bound together the extremities of the heaven with the extremities of the earth, making the nether extremities of the heaven rest upon the four extremities of the earth, while on high he formed it into a most lofty vault overspanning the length of the earth. Along the breadth again of the earth he built a wall from the nethermost extremities of the heaven upwards to the summit, and having enclosed the place, made a house, as one might call it, of enormous size, like an oblong vaulted vapour-bath.
What Cosmas pictured was in essence the earth as a canopy bed.
Besides Biblical arguments, Cosmas used logic to try to deflate the idea of a round earth. If people stood on the opposite ends of the supposedly spherical earth, how could both be standing upright and neither fall off? "When it rains upon both of them, is it possible to say that the rain falls down upon the two, and not that it falls down to the one and falls up to the other, or falls against them, or towards them, or away from them?"
Another person who questioned the idea of a spherical earth was the philosopher St. Augustine (A.D. 354–430), who wrote: "As to the fable that there are ... men on the opposite side of the earth, where the sun rises when it sets on us, men who walk with their feet opposite ours, there is no reason for believing it. Those who affirm it do not claim to possess any actual information; they merely conjecture."
Despite the flat-earth theories that were circulating, there were those who still believed that the earth was round. A learned monk called Venerable Bede (c. A.D. 672–735) was one of those who believed that the earth was indeed spherical. Ultimately, the only thing that would settle the question for good was more exploration of the world.