Environmental Engineering Reference
In-Depth Information
Chapter
25
Mountain environments
No landsystem inspires emotions quite like mountains, which are hostile, rugged and
remote in their physical character. They inspire awe and promote strong spiritual
emotions and associations, often thought of as the abode of gods. As such they are central
to a number of religions but peripheral to most people's lives. Mountains mark ethnic
frontiers and political boundaries dividing peoples and yet are home to others. The Incas
and Tihuanacos of South America and the Kurds, Tibetans and Nepalese of Asia suffered
persecution by intolerant societies and mountains provided a refuge or barrier against
political storms throughout history. The mountains of Afghanistan, Kashmir, Iraq and the
former Yugoslavia are among Earth's more intractable battlegrounds. Mountains form 20
per cent of continental land surfaces but understandably house only 10 per cent of world
population. They influence a further 40-50 per cent of us indirectly through their
resources and their role as global 'weather makers' and 'water towers' - denoting their
impact on planetary and synoptic meteorology and hydrology - and sustain 24 per cent of
global tourism.
PHYSICAL GEOLOGY OF EARTH'S PRINCIPAL MOUNTAIN
SYSTEMS
Mountain environments create high-energy, high-stress and high-sensitivity landscapes
carved from orogenic episodes of Earth history. The three most recent, Phanerozoic
events are still clearly imprinted on continental land surfaces. Their formation and
relocation by plate collisions defies conventional geographic patterns and concepts of
morphogenetic regions based on climate zones (Figure 13.3). Mountains extend almost
continuously for 29,000 km through the Americas-Transantarctic mountains, from pole
to pole and through every latitude across the equator. The Tethyan orogens extend across
150
°
of longitude from Morocco through south central Europe, the Middle East and
central Asia to Indonesia.
Altitude
simulates
latitude
, replicating the eco-climatic gradient
of 90° of latitude in just seven vertical kilometres in the equatorial Andes. Their spatial
distribution is set by the supercontinental cycle, and its impact on representative
mountain systems is examined now.
THE AMERICAS: ANDES, ROCKY MOUNTAINS AND COAST
RANGES
Differences between the American cordilleran systems are explained by asymmetrical
motion of the American and Pacific basin plates noted earlier (Chapters 10, 11). Both
continental orogens are of late Mesozoic to Quaternary age but include exposed or
