Yosemite is filled with granite rocks. I did some research so that I could teach my kids and share with you some interesting things about granite. Millions of years ago granite was formed deep inside of the earth. At about 40-60 miles below the ground there is a liquid called magma. Under very hot temperatures, the liquid minerals (quartz, feldspar, mica and hornblende) mix with the magma and under large amounts of pressure, slowly cools down.
As the cooling process begins, the magma and the minerals interlock like pieces of a puzzle. This makes the rock strong, hard and very durable.
The magma and minerals cool and solidify very slowly below the earths surface. During this process large crystals come into formation.
Because all of this happens beneath the earths surface, granite is known as igneous rock. Igneous rock is the oldest kind of rock. It is also the hardest rock that we know of.
Igneous rock is found all around the world. But Yosemite is home to the largest single piece of solid granite in the world. That's right, El Capitan is the largest single piece of solid igneous rock rising 3,593 feet out of the ground.
Horsetail Falls and El Capitan
The granite rocks provide lots of natural cracks and crevices that allow rock climbers to get good hand and foot holds when scaling the rock.
When I look closely at granite I see light and dark minerals. The black grains are the mineral mica. The gray grains are the mineral quartz. The white grains are the mineral feldspar. And other darker minerals are the hornblende. When you are here in Yosemite, you can see the minerals and crystals very well in person. Pictures do not always do justice to what we see in person!
When you come to Yosemite you will see domes, spires, arches, sheets and huge blocks of igneous rock. Some of the mountains are jagged, some are as smooth as can be. The terrain varies considerably...but it is all spectacular!
I often see rocks that are split and they are called fractures or joints. This is where water or glaciers have found a weak spot and split the granite. Half Dome and El Capitan have the least amount of fractures of all the rock here in Yosemite.
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