ABSTRACT
Physical geography of mountains Physical geography generally encompasses climate and weather, landforms and geology, and ecosystem biology. In mountain regions, especially, these three areas of study are intricately intertwined, shaping variations in the experience and attraction of mountains as trekking destinations. This is because climate conditions change rapidly with elevation, resulting in vegetation zones at different heights and in different micro-geographies. In lower latitudes (away from the north and south poles), the altitudinal zonation of a mountain with significant topographic prominence (elevation difference between its base and its peak), can vary from either deserts or tropical rainforest conditions at its base, through temperate deciduous and pine tree ecosystems in its middle elevations, then a thinning of vegetation leading to a treeless tundra at its peak. Mauna Kea, on the island of Hawaii, offers an example of this, rising from sea level to 4,207 m (13,803 ft) in elevation. Tropical rainforests hug its lower northeast facing windward side, which receives consistent humid trade winds throughout most of the year. These winds rise up the slopes of Mauna Kea, forming clouds and up to 500 cm (200 in) of rain a year as the humid air encounters colder temperatures. Meanwhile, dry desert conditions (with less than 15 cm (5 in) of rain a year) are found on its western leeward slopes where descending air expands and dissipates its clouds by the time it reaches the popular Kona Coast resort area. These two extremes in the lower slopes give way to a more temperate grass and forest zone (up to the 3,000 m (9,800 ft) elevation), which turns to a shrub and treeless peak that is often covered with snow in winter and even shows evidence of past glaciation. Altitudinal zonation patterns are especially prominent in tropical and subtropical environments where people seek out the cooler weather at higher elevations to escape the heat in the lowlands below. Hill stations became popular leisure and trekking destinations during the colonial era in humid South and Southeast Asia (Jutla 2000), while high mountain peaks in desert areas in Central Asia, the Middle East and the American southwest create islands of temperate ecosystems surrounded by a sea of aridity. In addition to cooler temperatures,
the less populated and less industrialized mountain destinations and regions also offer cleaner air and an escape from urbanization. Global climate change, however, is starting to have significant impacts in mountain environments, with high alpine ecosystems showing greater sensitivity to atmospheric fluctuations, especially shorter winter seasons and declining mean snow levels (Nyaupane and Chhetri 2009). Ski industry responses to warming conditions have included a significant increase in non-snow activities, including trekking, which can now be undertaken over a longer season (Steiger and Stötter 2013). Geomorphology is the study of the Earth’s surface, including continental drift (plate tectonics), mountain building processes and surface erosion processes. These geomorphological processes are slow, but consistent, as they reshape the surface of the planet, creating the spectacular mountain landforms that inspire hikers, trekkers and climbers. Although the planet Earth seems to be a solid, it is actually more of a hot liquid ball, with only the outermost 1 per cent (5 to 50 km; 3 to 50 mi) comprising a solid crust that we can stand on. A constant churning of the molten inner core results in uplifts that cause the hard crust to crack and shake, which is felt as earthquakes. The lightest material in the Earth’s crust has gradually come together to form the continents, which float on top of the heavier igneous rock that comprises most of the crust. The continents are pushed around by the churning core, resulting in continental drift. The major mountain chains of the world were pushed up when large chunks of the Earth’s crust (consisting of both continents and ocean floor) collided in this drift process. As soon as they were pushed up, however, weathering processes (rain, snow, wind, rivers, waves and glaciers) began to erode them down, sometimes creating smaller hill and valley systems. Most of the older mountains ranges of the world were formed about 360 million years ago when all of the continental land masses moved together to form the single land mass of Pangaea (‘all lands’). Many large mountain chains were created from the colliding and coalescing continents. Approximately 200 million years ago, Pangaea started to break up into the separate continents that eventually became what we know today. The older mountains that were formed by Pangaea (including the Ural range in Russia, the Carpathian range in Eastern Europe, and the Appalachian range in the US, among others) stopped growing at that time and have been eroding ever since. New mountain ranges, however, began to emerge from the breakup of Pangaea, and most of them are still rising today. The younger mountain ranges of the world are generally clustered into the the Alpide Belt (extending from the Alps in Europe, through the Himalaya and Tibetan Plateau in Central and South Asia, and down to the islands of Indonesia in Southeast Asia) and the Pacific Ring of Fire (extending from the Andes in South America, up through the Rocky Moutains, Coast Mountains and Aleutian Islands of North America, then south to Japan, Taiwan, the Philippines and New Zealand). Each of these two global systems is broken down through a tree-like system from major mountain chains,
to smaller ranges and individual mountain groups and peaks. Excluding underwater oceanic mountain systems, the Andes are considered the world’s longest continuous mountain system at about 7,000 km (4,350 mi) in length.
