external geological agents are responsible for the modification of land relief from the effects of external geological processes.
water, which acts in several ways:
Rain, eroding the soil and pulling out little pieces that are drawn. Rivers
, wearing the mountains are born and formed gullies and canyons. Ice
, as the temperature drops the rain-soaked rocks are frozen and the water from its cracks, the increase in volume (ice), press on them until the fracture. Mares
, waves erode the softer rocks of the projections coastal and ocean currents that are dragging sand beaches.
Rainwater that seeps into the interior can dissolve some of the limestone to form large cavities, called caves and underground rivers.
The wind , drag small pieces of land as the rocks hit the wear (erosion)
The vegetation , break rocks with their roots or down the mountain soil preventing it from being swept away by the rains. The man
, whose activity changes and changes the landscape.
Weathering is the disintegration and decomposition of rock at the surface or close to it as a result of exposure to the elements, with the participation of biological agents.
WEATHER: Influence of different variations from one region to another land. With changes in land cover, precipitation, freeze-thaw action
lithologic factors: Influence rocks and presence of fractures and joints in rocks
TYPES OF WEATHERING
mechanical weathering: the physical disintegration of rock fragments due to temperature changes, moisture and biological activity.
After mechanical weathering acting agents, surfaces created by the different fragments are disposed to action ...
Chemical weathering is the chemical transformation of the rock causing the loss of coherence and rock alteration. The most important processes are the atmospheric water vapor, oxygen and carbon dioxide. Processes that act
in mechanical weathering
Lajamiento : Formation of joints close to each other
Termoclastia consisting of rock fragmentation due to sudden temperature changes. The expansion and contraction caused by changes in temperature cause stress in the rocks that break eventually.
To produce this break abrupt changes are needed in very short periods of time as those that occur in arid deserts, but also rocks allow color and texture and decrease absorption of heat radiation.
also must have a mineral composition that allows differences expansion and contraction, so that tensions are effective.
Gelifracción or crioclastia
consists of rock fragmentation due to the stresses produced by freezing and thawing of water in the holes making the rock. The increased volume that produces frozen water acts as a wedge, which eventually break up the rock ...
This means that for gelifracción work is necessary to have frequent freeze-thaw cycles that occur in the mid-latitude periglacial type processes. At high latitudes with glacial-type processes such alternations do not occur, as the freezing period lasts for months. Http://feedjit.com/join/
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