Tuesday, November 12, 2019

Geology Through Literature - Leaves of Grass

Geology Through Literature: Leaves of Grass

Leaves of Grass by Walt Whitman exudes beautiful descriptions of the natural environment around all of us. This includes many geological terms being thrown about such as "gneiss" and "coal". Without any context though, those words are just ... words. But there is one line that provides a great geological context:
[Song of Myself]
"...In vain the plutonic rocks send their old heat against my approach..."
Although this is a simple line, it actually provides a great deal of insight. Plutonic rocks are a variety of igneous rocks. Igneous rocks are a type of rock that forms from molten/liquid rock. There are two main varieties of igneous rocks. They are known as external igneous rocks and internal igneous rocks. 

External igneous rocks, also known as volcanic rocks, form from molten rock that has erupted to the surface of the earth (i.e. lava) and solidifies there. These types of rocks have no visible crystals within them because they cool so quickly.

Internal igneous rocks, also known as plutonic rocks, form from molten rock that has not erupted to the earth's surface and remains within the earth (i.e. magma). Since these rocks cool within the earth they cool a lot slower allowing the crystals within them to grow much larger than volcanic rocks.  Granite is a common type of internal igneous rock. The earth provides a type of blanket to these molten rocks allowing the heat to remain within them for a lot longer. This leads to the "old heat" reference in the text from the plutonic rocks. 

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