Many of the ridges left in the Appalachian Mountains are mainly quartzite.
Quartzite is one of the hardest rock formations found on earth. In glaciated regions it frequently forms the scarred ridges, cleaned of all other minerals and rocks, that was simply too hard for the ice to wear away. Composed primarily of silicon (like quartz) it also contains trace amounts of other elements that can give both strength and color to the rock, like the pink that results from iron impurities. Quartzite undergoes a long formation process that is a sample of the full rock cycle.
Instructions
Changing Sandstone Into Quartzite
1. Quartzite begins its formation as a relatively pure deposit of quartz sand which is finally compressed and chemically fused into rock. The environment where such pure sandstone can be developed is normally either a shore where waves sort out the softer, finer and lighter materials. It can also develop along a river's edge or in deltas where the water current performs the same sorting function. The reason that iron is often found as part of quartzite is because it is one of the heavier minerals and resists the sorting action of water.
2. The next step in the change from sandstone to quartzite is the collision of one of earth's plates with another, much as the Pacific plate continues to collide with the ancient North American plate. In earlier epochs that collision created all of the west coast states and provinces as smaller island landforms (called terranes), which were carried along with the Pacific Plate and crashed into the North American plate. The Rocky Mountains, which are largely up-thrust sedimentary rocks, are the edge of the contact zone. Most of California, Oregon, Washington, and British Columbia are ancient terranes (island continental systems) that crashed into North America and welded into place.
3. Any sandstone part of the Pacific Plate itself, or part of a terrane, could either be forced upward in a plate tectonic collision or forced to dive deep into the earth underneath the other plate. These contact zones are known as "subduction" zones because one plate is being pushed under the other. In that environment, a plate is pushed closer to the molten magma of earth's interior and subjected to immense pressure, causing the sandstone to re-melt. As it cools, it crystallizes into tightly intertwined quartz crystals. The resulting rock formation is very hard and when fractured breaks across all the old sandstone structures.
4. A metamorphic rock forms in a two-step process. First it is originally either a sedimentary rock or an igneous rock. When those original formations are subjected to intense heat and pressure they melt, resort themselves chemically in the molten state, then re-crystallize and cool as metamorphic rocks. Because of its high quartz content, sandstone becomes quartzite.
Tags: American plate, crashed into, crashed into North, into North, North American, North American plate, Pacific Plate
