[MUSIC] Clearly mountains matter a lot. They're important for a whole host of reasons to people all over the world. But what exactly are mountains? What makes a landform a mountain? Is it the size of a landform that's the determining factor? Is it its elevation? If so, how big or how high must a landform be to be called a mountain? And what about other factors like terrain factors, steepness of slope for example. [SOUND] Let's consider some of the criteria, including size, elevation, and terrain, to try to get closer to a workable definition of a mountain. Roderick Peattie in his classic 1936 book, Mountain Geography, suggested several subjective criteria for defining mountains. Mountains should be impressive. They should enter into the imagination of the people who live in their shadows. Mountains should also have individuality. Peattie uses Mount Fuji in Japan and Mount Etna in Italy as case studies. Both are big snow-capped volcanoes that dominate their surroundings, and for centuries they've been celebrated in art and in literature. But they produce very different responses in the minds of the people who live near them. Mount Fuji is benign and sacred, a symbol of strength, and peace. Here in this 19th century wood engraving, it figures as a symbol of stability, amidst the wild and chaotic world. Great Wave Off Kanagawa, is one of the best recognized works of Japanese art, in the world. Mount Etna on the other hand, is menacing and devilish. Threatening to bring down lava and fire on nearby farms and communities. It remains today the most active volcano in Europe. For Peattie then, a mountain is a mountain because of the role it plays in popular imagination. It can hardly be more than a hill but if it's distinctive, and plays a symbolic role in the lives of people, it might well be considered a mountain by those who live near it. >> It's tricky to include such intangibles in a workable definition. A more objective basis for defining mountains might be elevation, its height above sea level. But how high does a landform have to be, to be a mountain? What height is required to qualify? Although elevation is an important criterion, it remains insufficient by itself. There are many landforms that are high, but wouldn't generally classify as mountains. Consider a plateau for example. A plateau is a high plain or table land, usually consisting of relatively flat terrain that's raised significantly above the surrounding area. Known as the roof of the world, the Tibetan Plateau, for instance, reaches an altitude of 5,000 meters above sea level. Or there's the very flat Antarctic Plateau. Its high elevations combined with high latitudes and extremely long sunless winters means that the temperatures here are the lowest in the world in most years. So elevation on its own doesn't quite do the trick, we need to look at the terrain. An objective definition of mountainous terrain should include the local relief, steepness of the slope, and the amount of land in slope. Local relief is the elevational distance between the highest and the lowest points in a given area. But how much relief is required for a landform to be considered a mountain? What amount is required for a place to qualify. Several early European geographers believed that for an area to be truly mountainous, there should be about 900 meters or 3,000 feet of local relief. But if this standard were applied, only the major mountain ranges of the world, like the European Alps, or the South American Andes or the Himalaya in Asia, would qualify. Other clearly mountainous regions, like the Appalachian Mountains in eastern North America, wouldn't be included. By itself, local relief, like elevation, remains an incomplete measure of mountains. Consider the spectacular relief displayed on a plateau when in sized by steep valleys. Think of the Grand Canyon on the Colorado Plateau for instance. Features like this are essentially inverted mountains. Still, this particular area of high local relief is of limited extent and is surrounded on either side by primarily flat terrain. We usually think of mountains as both elevated and dissected landscapes. The land surface is generally inclined, and the slopes are typically steeper than those of the surrounding low lands. The amount of steeply dissected land depends greatly on an area's geological history and great variation exists around the globe. In the Alps or Himalaya for example, steep serrated features are dominant. Whereas in other regions, these features may be more confined. The North Cascades of Washington is distinctive for its volcanoes, standing high above the upland surface. In the nearby American Rocky Mountains, broad and gentle summit uplands fill out and define the landscape. Mountains may also be defined by their geology. Most mountain chains have distinct and visible physical characteristics. Faulted or folded strata, metamorphosed rocks, or granite batholiths which reveal their composition and structure. These characteristics are used to describe the processes by which, over great stretches of time, they were built up and constructed. Mountainous terrain also results from destructive processes like constant erosion. Forces of wear and tear which beat down, carve out, and make smooth the surface of the Earth. Another way we can define mountains is by their climatic and vegetational characteristics. Significantly different climates, at successive levels or zones, are one way we might differentiate a mountain from say, a hill. Climatic variation is typically reflected in the vegetation, giving mountains a vertical change in plant communities, or bioclimatic belts, from bottom to top. One of the most distinctive characteristics of mountains, in addition to high relief and steepness of slope, is the great environmental contrast all within a relatively short distance. >> All of these various ways of defining mountains today rely on detailed analysis of one or more factors. They're also commonly based of off field work, ground based topographic mapping, mountaineering and other methodologies from across various disciplines. You see? To know mountains really is to be interdisciplinary. A universally accepted definition of what a mountain is will always be challenging. But perhaps Alton Byers, Larry Price and Martin Price in their recent book Mountain Geography, Physical and Human Dimensions get us the closest. >> A formal definition of a mountain is it is a conspicuous elevated land form of high relative relief. What does that really mean? Well if you think about the top of Mount Everest, which is nearly 9,000 meters high, it's local relief is down to the Tibetan Plateau which is about 4,500 meters high. And that means that you have a very large height difference, nearly 4,500 meters which is really what defines Mount Everest as a mountain in comparison to the flat land around it. Land can be high but flat, such as the Tibetan Plateau which is higher than all of the Alps of Europe. And of course over that relatively short distance of elevation gain, you have steep slopes. And the steep slopes also characterize mountains, you know a mountain when you're walking up one. As you go up a mountain it tends to get colder, windier and the amount of solar radiation increases. And that is reflected in the types of vegetation you get as you go upwards. From forests, to grassland, to tundra, to rocks, and snow and ice, if you're high enough. So, all of those things also define a mountain. But a mountain is also defined by the people who live around it, so if you live in a low flat place, like Florida, there is something called Iron Mountain which is a mere 100 meters high. But for people living there, it's something that they recognize as their highest point and therefore they think of it as a mountain. So to summarize, a mountain can be defined objectively in terms of its altitude, its slope and its local elevation range or lumpiness. But it can also be defined in terms of its characteristics such as its climate, it's vegetation and also by the people who live around it for whom it has meaning. >> Finally, confusion sometimes exists regarding the definition of three English words commonly used to describe the vertical dimension. Elevation, altitude, and height. While used interchangeably in everyday non-technical English, we thought it'd be useful to provide some explicit definitions. Elevation is the vertical distance between a point on a land surface and a reference point. Usually the mean sea level. Altitude is the vertical distance between an object such as a bird, aircraft or cloud and a reference point, where the object is not in direct contact with the reference point. The reference point can often be the mean sea level. Commercial airlines refer to altitude in this fashion. It can also be the land surface when describing the altitude of clouds, for instance. Height is the vertical distance between the top of an object, such as a tree or building or person, and the land surface where the object is in direct contact with the ground. So it's a measure of how far something protrudes above the land surface. While the differences and the definitions of elevation, altitude, and height may appear subtle, such differences are an important part of the framework of scientific communication. >> That nearly brings us to the end to our first lesson on why mountains matter, but before we conclude there are few more things that you need to do at the end of each lesson. >> To get you thinking about mountain geography we have an interactive learning tool that we call your personalized mountain world. It's your very own interactive map that will keep track of the places we visit during the course. Your challenge is to identify the mountain places we've discussed during the lesson. You'll be given a list of the locations we've covered. Independently, and without the use of aids, try to find each of these places on your map. Once a location is correctly identified, that location will remain on your personalized mountain world for the duration of the course. >> At the end of most lessons you'll also find a tech tip. Throughout mountains 101 we'll provide you with an overview of the mountain world, but we also want to share with you a series of practical tips and tricks to safely enjoy your time in the mountains. To do this, we've enlisted Canadian mountain guide Matt Peter and field ecologist Laura Redmond. They'll share information on topics from picking the best footwear for hiking to best avalanche safety practices. >> At the end of each lesson, you will also need to complete a short quiz. This proves that you know your stuff, and allows you to move on to the next lesson. >> And if you're interested in learning more about any of the topics that we discussed, we provided some supplemental material at the end of each lesson. So good luck, we hope you enjoy these end of lesson modules and we'll see you next time for a lesson on earth science and the origin of mountains.