Lovers' Leap EarthCache
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In this Earth Cache, you are observing the rocks of Lovers’ Leap and those in the Kenduskeag Stream, trying to determine the reasons for the weathering that has created the formation in front of you. As an Earth Cache, there is no 'container’ to discover. Rather, with this cache, you discover something about the geology of the area.
Not winter friendly as the city removes the signage each year from late fall to spring. Sign is badly damaged and now not part of the earth cache.
Lovers’ Leap Park is where the Kenduskeag water tumbles into an “S” turn through a gorge in the city’s most prominent bedrock outcrop with the 150’ high cliff known as Lovers’ Leap. The park is closed 10 PM-6AM.
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 environment 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 pressure. Mechanical weathering is the cause of the disintegration of rocks. The rock size is broken down into smaller particles but the rock components themselves are 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 break down combined with organic material to create 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 deficient in one or more minerals for good fertility, while a soil weathered from a mix of rock types often makes more fertile soil.
LOGGING REQUIREMENTS:
To receive credit for this 'find' please e-mail to my profile the answers to the following questions. Include the name of the Earth Cache at the beginning of your responses.
1- Notice the rock formations in front of you. 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- Ravines through bedrock are rare in Maine. How did this ravine get cut through the ancient (Silurian, over 400 million years old) bedrock visible here? At one time the signage provided the answer. Now to prove you’ve visited this earth cache count the number of posts on the overlook platform. Attribute: Not Winter friendly- Signage removed each winter and replaced in the spring.
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 accidences of rain are 2-3X normal.
Carbonation - This takes place when rain combines with carbon dioxide. It has an effect 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 aluminum and iron containing compounds in the soil beneath them. The decaying remains of dead plants may form organic acids which, when dissolved in water, causes chemical weathering
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, and 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 disintegration -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 crystallizes 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 rock face 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 pressurized air cracks away fragments at the rock face and widens the crack itself.
Salt-crystal growth – This type happens with the disintegration 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 pressure on the confining rock. It is normally associated with arid climates where strong heating causes strong evaporation and therefore salt crystallization. It is also common along coasts.
Biological weathering - Living organisms may contribute to mechanical as well as chemical weathering. Lichens and mosses grow on essentially 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 micro layer of the rock. On a larger scale seedlings sprouting in a crevice and plant roots exert physical pressure as well as providing for water and chemical infiltration.
Note: Eagles have been spotted perched above Lovers’ Leap.
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