Watson LakeThis is a sunset in part of the Colorado Plateau known as the Granite Dells. Watson Lake

Watson LakeThis is a sunset in part of the Colorado Plateau known as the Granite Dells. Watson Lake was dammed a century ago to create stable water supplies for the nearby city of Prescott and the surrounding areas. The rocks have the characteristic, boulder weathering style of granitic igneous rocks. Granites are tough; the minerals in granites don’t easily undergo chemical weathering and because the crystals are large, there isn’t a lot of surface area where water can get in-between grains to force the rock apart. The only place that water gets into a rock like this one is where the rock is already fractured, and usually granites form large fractures called joints every few meters as they approach the surface. Water gets into the rock along these fractures and weathers the rock to large, rounded boulders.This granite is 1.4 billion years old. It is one of many granites in this part of Arizona; a belt of ancient igneous rocks cross cuts the country and is a remnant of the assembly of this part of the continent. The original continent of Laurentia grew by the growth and addition of several large mountain ranges at this side between 2 and 1 billion years ago; this granite is the remnant of one of them.-JBBImage credit: https://flic.kr/p/NSDsvZReference:http://bit.ly/2p32elBhttp://europepmc.org/abstract/med/2917844 -- source link

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