Igneous Rock Is One of the Three

Igneous rock is one of the three main types of rock formations making up the earth's crust. It is formed primarily through the cooling and subsequent solidification of magma or lava. Igneous rock may also form without any crystallization -- below the surface as intrusive rocks or above as extrusive. It is best to think of igneous rock as being formed with heat -- one or more of three processes: temperature increases, decreases in pressure, or changes in composition. There are a number of types of igneous rocks; at least 700 have been cataloged, with most being formed deep within the earth's crust.

To describe the events that take place to move igneous rock from deep within the earth's core to the surface requires an understanding of the rock cycle. This is a concept that describes how rocks move and evolve into other types of rock or onto the surface through natural processes. These processes include plate tectonics, the water cycle, weathering, and erosion. For instance, because of the heat and pressure of the earth, rocks under the surface are often pushed into magma, and igneous rock when cooled. Cooling sometimes releases gas, which tends to push the rocks upward. As rocks are exposed to high temperatures and pressures, they can be changed physically and chemically into metamorphic rock, and then when pushed into the atmosphere through weathering and erosion become sedimentary. Uplifting of these rocks from deep under the surface accelerates the process and pushes the rock into the atmosphere, where cold, ice, rain, and the heat from the sun contributes to weathering.

3. Plate tectonics describe the large-scale massive motions of the Earth's outermost shell, the lithosphere. This crust is broken up into plates which, on earth; there are 7-8 major plates. Where the plates meet, their motion determines the type of boundary: convergent, divergent, or transformatory. Most of the major geologic events we know of occur at the juncture of those plates: earthquakes, volcanoes, mountain-building, and ocean trench formation. These plates are composed of different rocks, and are able to move because the crust has a higher strength and lower density that that of the underlying atmosphere. Movement results from a combination of gravity, motion from the sea floor, and the rotation of the globe and tidal forces.

Collisional plates happen when two continental plates form, often pushing up rock from beneath the surface and combining types; igneous and metamorphic for one, since both form deeper inside the crust out of pressure and heat. Because of the tremendous force when these plates hit, solid rock splits and rocks pile on top of each other, and mountains form. These also form under the oceans, resulting in mountain ranges and deep canyons that are as high as the Himalayas, but unseen. The basic premise for this is that continental crust cannot subduct due to its composition (too light and too thick). So when the oceanic crust between two continents is subducted, collision occurs. Folded Mountains

COLLISION PLATE BOUNDARIES:

4. Stellar evolution is a process in which a star changes over time. Depending on the mass of the star, this can range from a few million years to trillions of years. All stars are initially born from gravity collapsing clouds of gas and dust, with the tremendous pressure causing fusion at the core. Stars like Sol (earth's sun) gradually grow in size until they reach the level of a Red Giant, which then, because of so much mass and pressure, causes the core to collapse into a dense white dwarf. Larger stars, with larger mass, can explode as they age and form a supernova, neutron star, or black hole. The steps in solar evolution are:

Birth -- the protostar begins with the collapse of a molecular cloud, and, depending on the mass, may become a brown dwarf or through hydrogen fusion and high temperatures, change the core into helium and become either a red dwarf (fusing hydrogen slowly) to supergiant (massive internal ovens). Sol is a midsize star with a lifespan of about 10 billion years.