Background to the Yuncan HEP plant. Protest over the Yuncan HEP plant. Some information about the pros and cons of dams just look at the 2 tables. Information on responsible tourism in Peru. The pros and cons of tourism to Machu Picchu. The mountain slopes of the Andes are used for a variety of farming practises. The best land can be found on the valley floors, but an ingenious system of terraces dug into the valley sides and held up by retaining walls has been used to bring the lands on the valley sides into food production.
The flat terraces help to hold up water in a region where there are marked shortages. Most crops are grown in the lower areas and include soya, maize, rice and cotton. However, the main staple crop of the Andes is the potato, and there are hundreds of different varieties found in the mountains.
Most farming is subsistence, with the food grown for personal consumption, but there is some commercial farming. Llamas have historically been used a lot in the Andes, as a form of transportation and to carry goods. Alpaca, a relative of the Llama, has been used to produce some of the finest cloth known to man, and is also produced in the Andes mountains.
The Andes mountains contains a rich mix of minable materials that are both very valuable and very useful to man. When the Spanish conquered South America their prime objective was to prospect for gold. Potosi in Bolivia was one of Spain's principle mines and produced lots of silver.
There exist large deposits of Coal, oil and natural gas, iron ore, gold, silver, tin, copper, phosphates and nitrates and Bauxite for aluminium within the Andes mountains. The Yanacocha gold mine in Peru is the largest gold mine in the world.
Here the Nazca Plate is subducting beneath the South American plate. Visit the Interactive Plate Boundary Map to explore satellite images of convergent boundaries between oceanic and continental plates. Two locations are marked to show this type of plate boundary - the Cascade volcanoes along the Washington-Oregon coast of North America and the Andes mountain range on the western margin of South America.
Effects of a convergent boundary between an oceanic and continental plate include: a zone of earthquake activity that is shallow along the continent margin but deepens beneath the continent; sometimes an ocean trench immediately off shore of the continent; a line of volcanic eruptions a few hundred miles inland from the shoreline; destruction of oceanic lithosphere.
When a convergent boundary occurs between two oceanic plates, one of those plates will subduct beneath the other. Normally the older plate will subduct because of its higher density. The subducting plate is heated as it is forced deeper into the mantle, and at a depth of about miles km the plate begins to melt. Magma chambers are produced as a result of this melting, and the magma is lower in density than the surrounding rock material.
It begins ascending by melting and fracturing its way through the overlying rock material. Magma chambers that reach the surface break through to form a volcanic eruption cone. In the early stages of this type of boundary, the cones will be deep beneath the ocean surface but later grow to be higher than sea level. This produces an island chain. With continued development the islands grow larger, merge, and an elongate landmass is created. Lucia, and St.
Vincent and the Grenadines are examples of islands formed through this type of plate boundary. Visit the Interactive Plate Boundary Map to explore satellite images of these three areas. Effects that are found at this type of plate boundary include: a zone of progressively deeper earthquakes; an oceanic trench; a chain of volcanic islands; the destruction of oceanic lithosphere.
This is a difficult boundary to draw. First it is complex and second, it is poorly understood when compared to the other types of plate boundaries.
In this type of convergent boundary, a powerful collision occurs. The two thick continental plates collide, and both of them have a density that is much lower than the mantle, which prevents subduction there may be a small amount of subduction, or the heavier lithosphere below the continental crust might break free from the crust and subduct.
Fragments of crust or continent margin sediments might be caught in the collision zone between the continents, forming a highly deformed melange of rock.
This crustal shortening increases the vertical thickness whilst reducing the width of the lithosphere in the collision zone imagine a car hitting a solid wall and so produces the fold mountains of the Andes. Continued subduction of the Nazca Plate brings sea water, locked in the ocean crust, deep into the mantle.
As the plate heats up the water is liberated, lowering the melting point of the mantle and causing partial melting. This produces magma, which rises and may be erupted explosively as andesite at the surface. Andesitic magma is less dense than the surrounding material, and can have a temperature of o C. It is viscous, trapping gases as it rises. The water and gases in andesitic magma account for the explosive activity of andesitic volcanoes, which typically lie dormant for many hundreds or thousands of years.
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