Friday, 6 November 2015

The Great Barrier

Some continents may be low and flat, but not one continent exists in which there are no mountains.

Mountains are the pulsing heart of regions with infrequent rain or little snow, because snow collects on high mountains in the winter to melt in the spring, creating a fluctuation of growth which make the growing season for plants and trees longer. And mountains don't just do that; they create barriers which can steer away heat and trap rain in parts of the world, usually on the eastern side of a mountain range. In this way the American Rockies created the Mississippi River Basin, an area of great growth and richness (although not in the cities) and the Andes created the Amazon Basin. The highlands of western China guards, to a certain extent, Beijing from the wind and dust of the Gobi Desert.

Mountains are one of the most important biomes in the world, and must be protected. In this blog entry, I am going to write particularly about low mountains.

Although low ranges of mountains are not as influential as big ones, they do make a big difference to environments. The natural ecosystems east of the Appalachian Range in the USA, or what's left of them anyway, are very different to the forests of the Range itself, or the plains behind them. The Appalachian Range forests are part of one big plateau, the top being light woodland and dense scrub, the bottom being tall, stately trees with little underbrush. The lands to the West are dry woodland and some grasslands, and the coastal vegetation is mostly open woodland dominated by low trees.

The forests, alpine fields, grasslands and equatorial forests of the Great Divding Range in Australia are completely different from the Appalachians. To the west are dry, hot, dusty grasslands, and to the east are coastal forests and ranges which vary from place to place. However, for the mountains themselves, it really depends on which part of the map you are pointing to. To the northernmost end of the range stand equatorial swamps of great size, spanning the large Cape York Peninsula, and just to the south of that is the Daintree Rainforest, the only rainforest in Australia, which contains some of the oldest species in the world.

To the south of this is a very large in which there are a few scattered hills, but overall the entire place is dry and dusty, like a desert except for periodic floods. Eventually these tablelands are broken by a vast tabletop mountain and a colorful range called the Carnarvon Gorge, which contains several spectacular gorges and slot canyons, pillars and layered tiers of bare rock. Further to the south, is the beginning of a large World Heritage Area, the Gondwana Rainforests. These forests have basically been preserved in time, and a thick layer of fog only the highest mountains can pierce, for 100 million years.

To the South of that is the Blue Mountains, a massive wilderness of narrow gorges, parts of which are so remote entire types of trees have been quite recently found there. Then the Snowy Mountains, the only area in Australia where snow settles. Finally, the mountain range curves to the West and ends with a group of razorback ridges called the Grampians.

An explanation of why the two mountain ranges are so different can be derived from their formation. The Appalacians were formed by a great uplift that began many years ago. This means the mountains were mostly uniform in height in composition. The Great Dividing Range of Australia was formed by a volcanic hotspot like Hawaii. This means that, like piece of paper being moved below a hole puncher, the earth's crust was repeatedly punctured by a magma plume, causing earthquakes, and volcanoes. During each "puncture", the volcanoes varied in size, intensity, and height, explaining why some parts of the Great Dividing Range was only uplifted in some areas whereas others are completely made of basalt or granite. This creates an incredibly varied landscape.

Of course, this does not mean all "uplift" mountain chains are uniform along their length. The Himalayas, for example, certainly aren't. This is because the Himalayas are made of a particular type of rock that only  weathers most in certain situations. The American Rocky Mountains are slowly being stretched apart so that the Southern part of the chain is lower than the northern part.

Wherever they are, however they are formed, however high they are, mountains will always serve as driving forces in the culture and prosperity of peoples around the world. They will always serve as "great barriers".

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