THE ROCK CYCLE IS A CONTINUOUS PROCESS through which old rocks are transformed into new ones. Rocks can be divided into three main groups: igneous, sedimentary, and metamorphic. Igneous rocks are formed when magma (molten rock) from the Earth’s interior cools and solidifies. Sedimentary rocks are formed when sediment (rock particles, for example) becomes compressed and cemented together in a process known as lithification. Metamorphic rocks are formed when igneous, sedimentary, or other metamorphic rocks are changed by heat or pressure. Rocks are added to the Earth’s surface by crustal movements and volcanic activity. Once exposed on the surface, the rocks are broken down into rock particles by weathering. The particles are then transported by glaciers, rivers, and wind, and deposited as sediment in lakes, deltas, deserts, and on the ocean floor. Some of this sediment undergoes lithification and forms sedimentary rock. This rock may be thrust back to the surface by crustal movements or forced deeper into the Earth’s interior, where heat and pressure transform it into metamorphic rock. The metamorphic rock in turn may be pushed up to the surface or may be melted to form magma. Eventually, the magma cools and solidifiesbelow or on the surface-forming igneous rock. When the sedimentary, igneous, and metamorphic rocks are exposed once more on the Earth’s surface, the cycle begins again.
The rock cycle
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GEOLOGY AND GEOGRAPHY AND METEOROLOGY
published on 5:34 AM
THE ROCK CYCLE IS A CONTINUOUS PROCESS through which old rocks are transformed into new ones. Rocks can be divided into three main groups: igneous, sedimentary, and metamorphic. Igneous rocks are formed when magma (molten rock) from the Earth’s interior cools and solidifies. Sedimentary rocks are formed when sediment (rock particles, for example) becomes compressed and cemented together in a process known as lithification. Metamorphic rocks are formed when igneous, sedimentary, or other metamorphic rocks are changed by heat or pressure. Rocks are added to the Earth’s surface by crustal movements and volcanic activity. Once exposed on the surface, the rocks are broken down into rock particles by weathering. The particles are then transported by glaciers, rivers, and wind, and deposited as sediment in lakes, deltas, deserts, and on the ocean floor. Some of this sediment undergoes lithification and forms sedimentary rock. This rock may be thrust back to the surface by crustal movements or forced deeper into the Earth’s interior, where heat and pressure transform it into metamorphic rock. The metamorphic rock in turn may be pushed up to the surface or may be melted to form magma. Eventually, the magma cools and solidifiesbelow or on the surface-forming igneous rock. When the sedimentary, igneous, and metamorphic rocks are exposed once more on the Earth’s surface, the cycle begins again.
