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Fine Art Rocks: Igneous rocks [5] are divided into extrusive and intrusive rocks. Extrusive rocks are those that were ejected by volcanoes and cooled as lavas on the surface of the earth. Intrusive rocks are those that solidified beneath the earth's surface. The grain or crystal size of a rock depends on how fast it cooled; coarsegrained rocks are the result of slow cooling which has given crystals time to grow to sizes greater than two millimetres in length. Rocks cool slowly when deep in the earth's crust and coarseness is characteristic of intrusive rocks. fine art rocks-grained rocks have cooled rapidly either on or near the earth's surface; most extrusive rocks are fine art rocks grained although some are cooled so rapidly that no crystals have time to grow and obsidian is formed.However, when they reach the surface to form lavas - such as basalt, obsidian and rhyolite (igneous rocks of very fine art rocks texture) -they are, as are sedimentary rocks, always younger than the rocks below them. Since the complete stratigraphical column has never been discovered in any one site (it would have a thickness of many hundreds of kilometres), assembling its highly fragmented sections in correct order requires geological detective work to correlate widely scattered beds of rocks.
They yield to some extent, but after reaching a certain limit, they fracture. Along major planes of movement rocks are thus fractured, first to fault or crush breccias, and then to rocks of ever decreasing grain size, in which the grains remain sharply angular. Such fine art rocks-grained fracture rocks are called my-lonites. |
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