Occasionally violent tremors result and cause the widespread destruction of an earthquake. The Alaskan earthquake of 1964 was caused by such a shift in the fault running along the western edge of North America. The Earth's landscapes have been created over millennia by the gradual shifting of continental plates and by the violent effects of volcanoes and earthquakes. These primitive shapes are in turn worked upon by other natural forces. Frost cracks the mountain rocks, glacial ice wind and water transport rubble into the lowlands. Rivers etch the valleys carrying small stones to the sea, where layer upon layer sand and organic matter is pressed to the ocean floor. These sedimentary layers are changed overtime by pressure and heat from deep within the earth. The many different types of sediment are transformed into a vast range of rocks, minerals and ores. Vegetation becomes the energy wealth of coal, oil and natural gas. Rock sediment becomes the hard metamorphic rock that gives us valuable ores, and the building materials we prize for their strength and decorative features. The most valued of all the rocks and the gems and semi precious stones mined from the earth are exposed at the surface by wind and water. The most prized of all is the diamond. The currents of molten rock force upward and build the rocks that release these precious stones. So too do they force the older layers of sediment downward. Eventually, the sinking rock contacts the enormous heat inside the earth, melts and returns once again to the cycle of eruption and continent movement that gives forth to the planet we live on.