Weather - The Earth Splits EarthCache
Hidden : 7/11/2014
Difficulty:
1.5 out of 5
Terrain:
2.5 out of 5

Size: Size: other (other)

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Geocache Description:


This Earthcache was setup to teach you about the weathering of the earth. To receive CREDIT for this 'find' please e-mail me at my profile the answers to the questions listed below. PLEASE send your answers BEFORE you log a 'find', as I would not want to DELETE your log !

The truly great part of this earthcache is that you can see how this split could be put back together. This Earthcache is located about 150 feet above the current level of Lake Michigan. This was not the case 10,000 years ago when this area of the Niagara Escarpment was covered by the Laurentide Ice Sheet. The glacier scraped almost all of the topsoil, that in most regions, would filter rain runoff. As the water percolates down to the dolomitic limestone, it has no problem making its way through to the water table. This is because dolomite tends to naturally fracture both horizontally and vertically. It creates fissures and crevasses called Joints. The stress fractures in the bedrock are exacerbated by the expansion of ice located in the cracks and joints during the winter months.
On top of the naturally fracturing dolomite, the limestone has a tendency to dissolve, creating larger cracks and in some cases caves. Earth cracks can be formed several ways. The way this earth crack was formed was by acidic rain water flowing through fractures in the limestone. Over many years the limestone was dissolved by the water thus enlarging the fractures. The weakened rock here was then subject to gravity causing the split.
CLIMATE & ROCK WEATHERING: Weathering is the direct result of the climate. It will determine the rate and type of weathering that occurs to a rock. The greatest weathering agent is water. All rocks weather differently over time. The amount of precipitation in an area determines the amount of weathering that can occur. The rate of weathering depends upon three main factors:
1- The minerals being weathered and their resistance to weathering
2- The climate
3- The amount of surface area exposed.

Weathering is the decomposition of the earth's rocks, soils, and minerals through direct contact with the atmosphere. Weathering occurs without movement, meaning that erosion is NOT considered to be weathering, though it may have caused the environment for weathering.
There ate 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 water, ice, pressure, lightening and expansion and contraction with heating and cooling. Mechanical weathering is a major cause of the DISINTEGRATION of rocks. The rock size is broken down into smaller particles but the rock components 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 rock components DOES change in chemical weathering.

TYPES OF MECHANICAL WEATHERING:
THERMAL EXPANSION - This type of mechanical weathering happens when there is a great CHANGE in temperatures on a cyclic basis. The stress of the temperature change causes the peeling off of the layers of rock into sheets. Thermal expansion is increased by moisture.
FROST DISINTEGRATION - This happens in environments with a lot of moisture and where the temperature often fluctuates above and below freezing. When the water freezes it crystallizes and expands, producing stress on the rock. Limestone and shale are especially vulnerable to this type of weathering.
BIOLOGICAL WEATHERING - living organisms may contribute to mechanical as well as chemical weathering. The attachment of organisms to the rock surface enhances physical as well as chemical breakdown of the surface micro layers. On a large scale, seedlings sprouting in a crevice and plant roots exert physical pressure as well as providing for water and chemical infiltration. Burrowing animals and insects disturb the soil layers adjacent to the bedrock surface increasing water and acid infiltration too.

TYPES OF CHEMICAL WEATHERING:
DISSOLUTION - Rainfall is acidic because atmospheric carbon dioxide dissolves in the rainwater producing weak carbonic acid. It is the cause of acid rain, and the acid level is 2-3 times the normal.
CARBONATION - This takes place when rain combines with carbon dioxide. It has an effect especially on limestone because the weak carbonic acid formed reacts with calcium carbonate.
BIOLOGICAL - CHEMICAL WEATHERING - A number of plants and animals may create biological/chemical weathering. The decaying remains of plants and the waste of animals from organic acids which when dissolved in water causes chemical weathering.

Please be respectful of this Natural Structure. LOGGING REQUIREMENTS ARE:
1 - Estimate the length of the fracture
2 - Estimate the depth of the fracture
3 - Count the number of layers of dolomitic limestone you see here
4- Determine if the 'weathering' that you see is PRIMARLY mechanical or chemical weathering.
5- List the TYPES of mechanical & chemical weathering that you observe.
6 - What is the direction that the fracture runs?
7 - Looking at each side of the fracture walls, describe the walls condition, rough or smooth and tell us how they became this way
8 - Not required, but we would love to see you Post pic of your team at the split.

PLEASE NOTE: I will not be sending follow up requests for answers any longer, if you don't complete the requirements, it will be deleted. To claim an Earth Cache you must follow through with the requirements, not just visit the site.

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