Rocks and Thier Durability

Essay by mustangcobra490Junior High, 8th gradeA-, April 2004

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Having just been notified that the PTO will grant my request to fund the building of a statute of my favorite teacher, I am left with the task of selecting which type of rock I will use. I will have to take into account how climate, physical weathering, chemical weathering, and biological weathering will affect my statue.

I have a choice of many types of rocks to choose from including marble, granite, rock salt, chalk, limestone, and sandstone. I can easily eliminated rock salt and chalk because of how easily they erode. Rock salt, when exposed to water will start weathering immediately and chalk likewise. I can't use sandstone either because it easily erodes when in contact with wind and rain. Physical weathering does too much damage to these rocks.

After eliminating the above rocks, I am left with limestone, granite, and marble. I won't be able to use limestone either because it is very fragile when exposed to acid rain.

No matter how rare it occurs, acid rain can cause a lot cracks and crevices to form. Later, when water freezes in the cracks, ice wedging can cause the statue to just fall apart. For this reason, I cannot use limestone either.

Now I am left with marble and granite. Of these left, I will choose granite because it is harder than marble. Granite and marble are similar but since granite is igneous rock, it is harder. Being harder, or denser, has many advantages. The harder the rock is, the tougher it will be to weather away. Since the statue will be in the Butterfly Garden, it is also in danger of biological weathering. The plant roots all around the statue will grow into any little crevice and expand. So the harder the...