Gatlinburg's 'weathering' of Rock Formations EC EarthCache
Gatlinburg's 'weathering' of Rock Formations EC
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As an EarthCache, there is no 'container to discover. Rather, with this cache, you discover something about the geology of the area.
To receive credit for this 'find' please e-mail to my profile the answers to the following questions.
IT SURE MAKES IT eaier IF YOU SEND THE ANSWERS SOON AFTER YOU LOG SO THAT I CAN ID YOUR ANSWERS WITH YOUR LOG!
LOGGING REQUIREMENTS:
1- Notice the rock formations in front of you. (From the small gorge on your right where some water is flowing to about 8 feet to the left). Determine whether the weathering you are seeing is PRIMARLY mechanical or chemical weathering.
2- List the TYPES of mechanical and chemical weathering that you have observed.
3- Submit a picture of yourself and group if you wish. Picture can be taken in the park across the road in the parking area beside the mountain stream.
(There is abundant parking in the small park across the road.)
In this earthcache, you are observing the rocks, trying to determine the reasons for the weathering that has created the formation in front of you.
Weathering is the decomposition of the earth's rocks, soils, and minerals through direct contact with the atmosphere. Weathering occurs without movement, meaning that such things as erosion are NOT considered to be weathering, though erosion may cause the enviroment for weathering (see below).
There are two types of weathering, MECHANICAL (PHYSICAL) and CHEMICAL.
MECHANICAL weathering - involves the breakdown of rocks and soils through direct contact with atmospheric conditions such as heat, water, ice and preasure. Medchanical weatheriing is the cause of the disintergration of rocks.The rock size is broken down into smaller particles but the rock components themselves ate not altered.
CHEMICAL weathering - involves the direct effect of atmospheric chemicals or biologically produced chemicals in the breakdown of rocks, soils and minerals. The composition of the rocks components changes in chemical weathering.
The materials left over after the rocks breaks down combined with organic material creates soil.The mineral content of soil is determined by its parent soil sources. Thus, a soil derived from a single rock type can often be defficient in one or more minerals for good fertility, while a soil weathered from a mix of rock types often makes more fertile soil.
TYPES of Mechanical Weathering:
Thermal expansion - This type of mechanical weathering happens when there is a great CHANGE in temperature on a cyclic basis. Examples include the desert where the rocks are baked in the daytime sun, then evening temperatures plummet. The stress of the temperature change causes the peeling off of the outer layers of rocks in thin sheets. Thermal expansion is enhanced by moisture.
Frost disintergration -This process can also be called frost shattering, frost- wedging or freeze -thaw weathering. It often happens in environments with a lot of moisture and where temperatures often fluctuate above and below freezing temperatures. When the water freezes, it crystalizes and expands, producing stress on the rock. Rocks that are porous are especially susceptible to this type of weathering.
Hydraulic action - This is when water, (generally from powerful waves) rushes into cracks in the rockface rapidly. This traps a layer of air at the bottom of the crack, compressing it and weakening the rock. When the wave retreats, the trapped air is suddenly released with explosive force. The explosive release of highly preasurized air cracks away fragments at the rockface and widens the crack itself.
Salt-crystal growth - Causes disintergration of rocks when saline solutions seep into cracks and joints in the rocks and evaporate, leaving salt crystals behind. These salt crystals expand as they are heated up, exerting preasure on the confining rock. It is normally associated with arid climates where stronog heating causes strong evaporation and therefore salt crystalization. It is also common along coasts.
Biological weathering - Living organisms may contribute to mechanical as well as chemical weathering. Lichens and mosses grow on essentionally bare rock surfaces and create a more humid chemical microenvironment. The attachment of these organisms to the rock surface enhances physical as well as chemical breakdown of the surface microlayer of the rock. On a larger scale seedlings sprouting in a crevice and plant roots exert physical preasure as ell as providing for water and chemical infiltration.
TYPES of Chemical Weathering:
Dissolution - Rainfall is acidic because atmospheric carbon dioxide dissolves in the rainwater producing weak carbonic acid. In the case of acid rain, the acidicness of rain is 2-3X normal.
Carbonation - This takes place when rain combines with carbon dioxide. It has an affect on rocks such as limestone or chalk. This takes place because the rainfall produces a weak carbonic acid which reacts with calcium carbonate.
Biological-Chemical Weathering - A number of plants and animals may create chemical weathering through the release of acidic compounds, like moss on roofs is classified as weathering. The most common form of biological weathering is the release of chelating compounds like acids by plants so as to break down aluminium and iron containing compounds in the soil beneath them. The decaying remains of dead plants may form organic acids which, when disolved in water, causes chemical weathering
Great USA weather/temp map: (visit link)
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