History_of_Rocks

Associate Level Material History of Rock Worksheet Write a 500- to 750-word explanation regarding the role of plate tectonics in the origin of igneous rocks. |The role of plate tectonics in the origin of igneous rocks is very important. Igneous rocks are formed within three main areas; at| |lithospheric plates that are pulled at the ridges of the mid-ocean areas, seduction zones are where the plates join together, and | |where the continental crust has been pushed together. There are two ideas that are voiced when it comes to igneous rocks. The | |first idea is that igneous rocks do evolve meaning they can change from one type of rock into another. The second idea is that | |rocks are not distributed randomly throughout the Earth. Certain types of rocks are usually found in a specific area for a | |particular reason, yet all of these are combined into the process of plate tectonics. The word igneous stems from the Latin word | |“fire”. Igneous rocks start out as a liquid hot material. The material could have been from lava that had been erupted at the | |Earth’s surface, un-erupted lava or magma at shallow depths, or even plutons (magma that is in a deep body). People usually think | |of magma or lava as a liquid comparable to liquid metal. However, geologists have found that magma is mostly a liquid that has a | |load of the mineral crystals in it and has the consistency of mush. Magma then crystallizes into a corporation of minerals and | |some of these minerals crystallize faster than the others. When these minerals crystallize they leave the remnants of the liquid | |that has a changed chemical composition. As magma cools it eventually starts evolving as it goes through the crust and interacts | |with other rocks. You can tell the types of these igneous rocks by the texture of the rocks from the mineral grain size. | |Extrusive rocks cool more quickly from seconds to months and have very small or invisible grains. Intrusive rocks cools slower and| |have small to medium sized grains. Plutonic rocks cool over a period of millions of years, far underground and can have their | |grains to be as large as pebbles. Intrusive and plutonic rocks have a phaneritic texture. Igneous rocks are put in different | |classes depending on the minerals that they contain. The primary minerals in these rocks are very hard such as, quartz, olivine, | |pyroxemses, feldspar, and amphiboles. These together are called “dark minerals” by geologists. They also contain soft minerals | |such as mica. The two main know igneous rocks are granite and basalt. Basalt is a fine-grained, dark material of magma intrusions| |and many lava flows. The dark minerals are rich in iron and magnesium and this is the reason that basalt is also called a mafic | |rock. Basal is considered mafic and could be either intrusive or extrusive. Granite is a light, coarse-grained and is exposed | |after deep erosion. In general, granite rocks are a less dense rock compared to basalt and actually float higher than the oceanic | |crust on top of the Earth’s mantle. The history and behaviors of granite rocks are among one of the highest geology’s most | |intricate and deepest mysteries (Murck, Skinner, & Mackenzie, 2008). | Write a 500- to 750-word explanation regarding the role of plate tectonics in the origin of metamorphic rocks. |Metamorphic rocks are formed when a rock changes after it undergoes an extreme temperature or pressure change. The temperature | |must be at a high enough temperature to change the matter and reorganize it within the rock without being hot enough to melt the | |rock. Hot magma makes it way to the surface by pushing itself to the convergent plate boundaries and divergent plate boundary. | |The magma has contact with other rocks as it begins to rise to the surface. The magmas is hot enough that it starts to heat up the| |other rocks around it and as these rocks start to heat up they start to change and turn into metamorphic rocks. The process of | |this is called metamorphism. During this process of rock change, many things are destroyed such as, vesicles, graded bedding, | |porphyritic textures, and stratification. When these materials are destroyed, new minerals are put into their place and create a| |new texture in the rock. This is a major group of rocks called metamorphic rocks that are the result largely from the continuous | |motion of plate tectonics. Metamorphic rocks can be formed from many different rocks such as sedimentary, previously metamorphose | |rocks, or igneous rocks. When a metamorphosis starts at a convergent plate boundary from intense pressure this is then called | |regional metamorphism. When two plates end up colliding, the Earth’s crust then folds and faults from the intense pressures that | |change the large areas of the earth’s crust into metamorphic rocks. An instance of the plate tectonic process of the metamorphic | |process would be mountain ranges. The metamorphic process occurs while the rocks remain solid. If the rocks reach the point | |where it can melt it then becomes an igneous rock. The minerals that are in the metamorphic rocks do not crystallize from the | |magma; however, they are only stable that high pressures and temperatures that are found deep tin the Earth’s crust. Light-colored| |sills and dikes of igneous rocks cut the metamorphic rocks and during the metamorphism new plate mineral grains start to form and | |grown in the direction of wherever the least amount of stress is and then produces a planar texture that is called foliation. | |Rocks that only has one mineral or ones that recrystallize in the absence of deforming stresses are not able to develop a strong | |foliation and then develop a granular texture, such as limestone. Mylonite develops whenever a shearing along a certain fracture | |forms then small grains by ductile destruction of larger grains. The main types of foliated metamorphic rocks could include | |schist, gneiss, slate, and mylonite. Important non-foliate or granular rocks include marble, granulite, greenstone, and quartzite.| |They are all distinguished differently by their textures and then are distinguished by their compositions (Murck, Skinner, & | |Mackenzie, 2008). | Murck, B. W., Skinner, B. J., & Mackenzie, D. (2010). Visualizing geology (2nd ed.). Hoboken, NJ: Wiley.