 You are clear for launch, and with that, shut down your visors, O2 on, and prepare for ignition to O2. You can copy that and um... Hey, it's Mr. Roush off again. So as we start into the physical geography of the world, I thought it might be good to review the basic types of landforms. We will begin by looking at those features on the land, and then we're going to venture off the coast. So let's begin by looking at the basic types of landforms. And when we talk about basic, there cannot be any landformer basic than the plane. Now, plane is simply a flat area, and while 70% of the earth is covered by oceans, the planes account for 50% of the earth's land area. Now planes are important because they are often major areas for agriculture. For example, 80% of America's great planes are used for farming or for livestock. Now the great planes are grasslands called steppes, and the savannah in eastern Africa is also a grassland. But not all planes are grasslands. For example, the Sahara Desert is also a plane, and planes can also be the home of forests. Now a plane is simply defined as a flat area. Now there are several processes that can create these flat areas. Chave among these is a process called erosion, which uses wind, water, and even ice to be able to move dirt and rock known as sediment. Here, wind, water, and ice either removes or deposit sediment to be able to create this level area. Now lava spreading across the land from volcanic eruptions have also created some of these planes of the world. And many of the planes of the world are coastal planes low laying areas next to an ocean. See when sea levels of the oceans fall, they expose what used to be the ocean's flat floor, and this becomes a coastal plane. Now this is what created the Atlantic coast, which makes up most of the southeast portion of the United States, as well as America's great planes in the center of the country. And I know what you're thinking, how can the great planes that runs from the northern portion of Texas through Kansas and up into Dakotas, how can that be a coastal plane when there isn't a single ocean nearby? Well there isn't one now, but around 100 million years ago, the Great Plains was on the coast of the western interior seaway that divided North America. Now when that sea receded, it exposed its ocean floor, which we now call the Great Plains. Now we'll start putting bumps on the ground. And here I want to warn you a bit about geography. Many of its terms do not have hard and fast definitions. This includes the definition for hills and mountains. The definition of a mountain is that it is an area that rises very high above the land around it, and that it is bigger than a hill. And what is a hill? Well it is usually around a natural elevation of land lower than a mountain. So a hill is smaller than a mountain, but how small does a hill or how big does a mountain have to be? And this is where the definition of what a mountain and what a hill gets vague. For example, this is the Taukat Mountain in Connecticut, but these are the Ocho Mountains in Scotland, and just for kicks, this is Mount Sunflower in Kansas. Generally, hills and mountains are really dependent upon what people want to call them. Now mountains do tend to have a steeper rise in its landscape. The steeper the rise, the more likely people will call it a mountain. Now although most mountains will have steeper slopes, this really doesn't apply as much to older mountains such as the Appalachians in America or the Urals in Russia. The Appalachian mountains are nearly a half billion years old and the Urals are nearly 300 million years. This means that the effects of rain, wind and ice have worn them down for millions of years in a process called weathering. So they are far more rounded than the Rocky Mountains, which is only about 80 million years old, or the Himalayas that are only about 50 million years. These younger mountains are going to appear much more angular and jagged looking. Now what creates mountains is the moving of the Earth's crust and what is known as plate tectonics. When continental plates collide, they'll fold in on themselves and create mountains in what is called convergent folding. If we have an oceanic plate collide with any other plate, it creates a special type of mountain called a volcano and what is known as convergent subduction. Now just like mountains, hills can also be caused by convergent folding. They can also be created when cracks in the crust may jut upward or they may even be the result of rock and soil left by large masses of ice called glaciers. Now if you go into the American Southwest, you may find a special type of platform called the plateau. Now a plateau is a flat elevated plane that rises sharply above the area around it on at least one side. Now these can be rather small such as these plateaus in these pictures where it can be huge such as the Tibetan plateau in Central Asia that is four times the size of Texas. Now plateaus are often created by the collision of tectonic plates which will raise the elevation of the area. The Tibetan plateau is actually formed by the same tectonic plate collision that created the Himalaya Mountains which are to the south. Now the angular steep monolith plateaus such as these have been further shaped by wind and water that have carried away softer rock. So those are the four major landforms to planes, mountains, hills and plateau. But what happens when we start putting water into the mix? Well first of all we have rivers, streams and creeks. A river is defined as a natural flow of water from a high elevation to a lower elevation due to gravity. Now in this course we will find that rivers have been incredibly important to the settlement of cities. Now rivers not only provide water and fertilize soil but they also are important to trade and transportation. And what is a stream or a creek? Well they are also water naturally flowing from a higher elevation to a lower elevation due to gravity but they are different sizes. Streams are smaller than rivers and creeks are smaller than streams. But just as we saw with the definitions of hills and mountains there is no hard and fast definition that says how big each must be to be able to call it such. But we do know that rivers can be huge. The Amazon River in South America is not only the longest in the western hemisphere but it is the widest in the world. In its wet season it can swell to over 25 miles wide. This is over twice the Mississippi's widest section of 11 miles across. But the impact of rivers can be much wider than that. Major rivers form what is known as a river basin. Now think of your bathroom sink which is also a basin. Now when you turn on the faucet all the water you put into it goes to one point to drain and this is essentially the same thing with a river basin. Within a river basin all the rain water that falls will either be absorbed into the ground where it will flow into creeks and streams and smaller rivers and finally into the main river of the basin. A river basin can be huge. For example the Mississippi River basin in America takes up most of the central portion of the United States stretching anywhere from the Rocky Mountains to the west to the Appalachian Mountains to the east. Now when these rivers flow they will pick up loose soil and rock called sediment and carry it downstream. Again this is an example of erosion. Now with all the rivers of a river basin flowing into one river this means that tons and tons and tons of sediment are moved by water. The Mississippi River alone carries 500 tons of sediment down river each year. Now once the river exits through a larger body of water such as the Gulf of Mexico in the case of the Mississippi the water of the river slows down. It loses energy and it starts to drop or deposit its sediment. This sediment will build up on itself and begin to create a landform known as a delta such as the Mississippi Delta or the Nile Delta in Egypt. Now sediment plays another important part when rivers flood. In flatter areas where rivers flow if there's lots of rain or if there is an increase in the amount of snow that's melting in the mountains upstream this may force a river to flood out of its banks. Now when the level of this river begins to recede much of the sediment would be deposited into the ground creating a very fertile area called an alluvial plain. Now along with the access to water and trade this alluvial plain along a river have made rivers an incredibly important places in human history. Now because gravity pulls water down to the lowest point a river will always be as narrow as its volume will allow. This is the reason why rivers create through erosion these shape valleys. But sometimes the currents of a river might be moving very quick as it comes out of much higher elevations and along with much softer rock these rivers instead of cutting a v-shaped valley will straight down creating what is called a canyon. A canyon is a valley with steep rocky walls and a narrow canyon might be called the gorge. The Grand Canyon is probably the best example of a canyon which was created by the Colorado River six million years ago in an area that was uplifted by tectonic activity. Now while rivers will cut either steep canyons or v-shaped valleys glaciers will create u-shaped valleys. A glacier is a huge massive ice that will slowly move due to gravity. Essentially think of a glacier as a river of ice a really really really big river. Take the Bering Glacier in Alaska which is 121 miles long 10 miles wide and one half mile deep. Because these glaciers are so massive as they move they will carve valleys into the earth's surface. But because glaciers are solid and not liquid like rivers they do not narrow as they cut deeper into the earth. Therefore instead of v-shaped valleys they'll create u-shaped valleys with steep rather than sloped sides. Now some of these valleys can be quite large and others can be more narrow depending upon the width of the glacier. Now when these glaciers cut narrow steep valleys into the sea the inlets they create are called fjords. Now fjords can be found in Alaska, Chile, Norway, New Zealand and just a few other places in the world. Now speaking of the seas let's talk about them for a few moment. First of all there are oceans seas gulfs and bays. Oceans are the largest bodies of water the Pacific the Atlantic the Indian and the Arctic are all oceans. And in 2000 the southern ocean was named as the fifth ocean of the world. Then there are the seas. You might have heard the term the seven seas before. In reality they don't actually refer to seas at all. Now the seven seas are the Arctic Southern and Indian Ocean along with the North and South Pacific and the North and South Atlantic. But they're actually though over 50 seas in the world. Now a sea is defined as being smaller than the ocean and located where a land and ocean meet typically partially enclosed by the land. But just as we've seen with the definition of hills and mountains some geography terms are hard to follow. For example the Saragossa Sea and the Atlantic doesn't have land boundaries at all and the Caspian the Arles seas in Central Asia are not connected to the ocean at all as they're totally landlocked. But generally think of seas as a portion of an ocean that comes into contact with land. Of course then we get to gulfs such as the Gulf of Mexico. A gulf is an inlet of the sea almost completely surrounded by land and then a smaller gulf is called a bay such as Galveston Bay. So it's probably best to think of bodies of water as as you're further away from land much much larger you have oceans and as these bodies of water get smaller and closer to land the oceans become seas then gulfs then bays. Oh by the way the Caspian Sea is often argued to be a lake instead of a sea. Now explain this debate when we talk about Central Asia later in this course but why many people believe the Caspian Sea is a lake instead of a sea is because a lake is a large body of water entirely surrounded by land. So what's the difference between a lake then and a reservoir and finally we have a clear distinction in our geography terms. A reservoir is a man-made lake created by building a dam on a river. The dam holds back the water which be then becomes the reservoir. Although commonly the names of reservoirs are named lakes such as Missouri's Lake of the Ozarks Lake Conroe near Houston or Lake Mead in Nevada and Arizona which was created by the Hoover Dam. Now a wet piece of land just out into the water and is surrounded by three sides we call this a peninsula and if the water completely surrounds a land we call this an island. And oh by the way if you take lots of different islands and put them together such as the Hawaiian islands or the Philippines this is what we call an archipelago. Then there are isthmuses and straits and these are essentially mirror images of each other. An isthmus is a narrow stretch of land that connects two larger bodies of land. Panama is a perfect example of an isthmus. It connects Central and South America while separating the Caribbean Sea from the Pacific Ocean. Now the isthmus' mirror image then is the strait which is the narrow stretch of water that connects two larger bodies of water. Now the Strait of Magellan is a great example. At its narrowest of just eight miles across the Strait of Magellan connects the Atlantic Ocean to the Mediterranean Sea. In this course we'll discover that straits are incredibly important because 90% of all the world's goods are moved by ships. This means that these straits can be choke points if countries or even pirates interfere with international trade. Now straits are just one example of how each of these landforms can have significant impacts upon human behavior and we'll be studying these as we progress throughout this course. And there is many different other ways in which geography of these landforms has impacted mankind in many different ways. But until then, keep on learning.