Week 2 - Igneous Rock - El Capitan

Several years ago, I visited Yosemite National Park with my family and saw the rock formation known as "El Capitan". While I did not know this then, I know now that El Capitan is composed almost entirely of granite. Granite is a member of the felsic class of plutonic igneous rocks due to its high concentrations of silica and alumina. It is clear that El Capitan was formed underground and later became exposed based on the texture of the surface. When magma is allowed to cool and harden slowly underneath the surface of the Earth, the rock crystals are allowed to grow to much larger sizes than in rocks formed by magma that cools quickly on the surface of the earth. These large crystals are visible to the naked eye in rock formations such as El Capitan.