Like most Earths material, rocks are created and destroyed in cycles. The Rock Cycle is a group of changes. Igneous rock can change into sedimentary rock or into metamorphic rock. Sedimentary rock can change into metamorphic rock or into igneous rock. Metamorphic rock can change into igneous or sedimentary rock. Igneous rock forms when magma cools and makes crystals. The rock cycle never stops!
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Igneous RockIgneous rocks- form in two very different environments. All igneous rocks start out as melted rock, (magma) and then crystallize, or freeze. Volcanic processes form extrusive igneous rocks. Extrusive rocks cool quickly on or very near the surface of the earth. Fast cooling makes crystals too small to see without some kind of magnifier. On the other hand, when formed at depth, igneous rock is termed intrusive. There crystals have time to form and in this case form large crystals that are visible to the human eye.
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Metamorphic RockMetamorphic Rock- Metamorphic rocks form when sedimentary, igneous, or other metamorphic rocks are subjected to heat and pressure from burial or contact with intrusive or extrusive igneous rocks. Heat and pressure from burial cause molecules of flat minerals like mica to line up perpendicular to each other. Deep burial means higher pressure and hotter temperatures, and very high temperature and pressures cause the formation of new minerals, and mineral grains. Low-grade metamorphic rocks like slate and phyllite break in flat pieces, and have a sheen on the surface. Schist is shiny, and many schists contain garnets, staurolites or other mineral crystals that have grown within the rock. Gneiss is a foliated metamorphic rock. Layers of dark and light minerals stripe the rock, and sometimes it is possible to see how the direction of pressure deep in the Earth changed as the minerals formed.
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Sedimentary RockSedimentary Rock- Sedimentary rocks are those rocks made up of pieces of other rocks. We call the pieces of rock "clasts" . A clast is a piece of rock broken off of another rock. Clasts of rock are eroded from larger rocks, transported by wind or water and deposited in a basin.After some period of time, the clasts are lithified . The sedimentary rocks we see today were once gravel, sand, silt, mud, or living things. We decide what to name sedimentary rocks based on the size of the clasts that make up the rock. For most sedimentary rocks, this is easy. Sandstone is made of sand, siltstone is made of silt, mudstone is made of mud and so on. The only hard ones to remember are conglomerate and breccia. Conglomerates are made up of rounded, gravel-size particles and breccia is made up of angular, sharp-edged, gravel-sized clasts. Limestone and chert are classified as sedimentary rocks, but most limestone and chert are grown by living organisms rather than broken from other rocks. Some limestones have fossils, but most limestones and cherts have recrystallized, and the remains of the creatures that made them are no longer visible.
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Minerals & Magma
Molten material is called magma and originates at depths of 50-250 km. Magma that reaches the surface can release trapped gasses and is now termed lava. Magma consists of three main components, liquids, solids, and volatile which are gasses dissolved in the melt. The most common of which are H2O, CO2, and SO2. Following Bowen's Reaction Series, minerals crystallize in a systematic fashion based on their melting points. During crystallization the composition of the liquid portion of the magma continually changes. All the minerals on Bowen's Reaction Series are silicates ! If a melt is low in silica and high in Fe-Mg then it will fully crystallize before the lower temperature stages occur. On the other hand, if a melt is silica rich and low in Fe-Mg then it will proceed further and may be absent of early formed minerals.Magma falls into two categories, Felsic & Mafic. Felsic is silica rich ( minerals such as quartz and feldspar ), light in color and have lower specific gravity. Mafic magma is silica poor but ferro-magnesium rich, dark in color, and has a higher specific gravity.
Volcanoes and it's hazards in BC
Mt. Garibaldi and Mt. Baker have been determined as dormant volcanoes, the closest volcanoes that represents a potential for volcanic damage to the Lower Mainland of British Columbia. Both Mt. Baker and Mt. Garibaldi are stratovolcanoes that are
the result of the dense heavier oceanic Juan de Fuca Plate subducting beneath the lighter, less dense North American Plate that has created the energy to produce these volcanoes along the West Coast of North America. Mt. Baker has been releasing steam, as recently as 2001, from Sherman Crater and is considered to be active. The last dated eruption of Mt. Baker was in 1870 and has been cooling off. In recent years, scientists have been looking very closely at the geology and past history of activity of Mt. Baker. They are not saying that Mt. Baker will erupt soon, but they are theorizing that it will probably erupt again. Although, Mt. Baker may not erupt in the near future it has been forecast that an eruption will occur at some point in the future. When Mt. Baker erupts it is expected to behave in the same fashion as Mt. St. Helens eruption of 1981. Where Mt. St. Helens virtually exploded under the pressure of gas buildup, spewing mainly hot rock and ash causing mudflows which blocked rivers and caused flooding far away from the actual volcano peak.
the result of the dense heavier oceanic Juan de Fuca Plate subducting beneath the lighter, less dense North American Plate that has created the energy to produce these volcanoes along the West Coast of North America. Mt. Baker has been releasing steam, as recently as 2001, from Sherman Crater and is considered to be active. The last dated eruption of Mt. Baker was in 1870 and has been cooling off. In recent years, scientists have been looking very closely at the geology and past history of activity of Mt. Baker. They are not saying that Mt. Baker will erupt soon, but they are theorizing that it will probably erupt again. Although, Mt. Baker may not erupt in the near future it has been forecast that an eruption will occur at some point in the future. When Mt. Baker erupts it is expected to behave in the same fashion as Mt. St. Helens eruption of 1981. Where Mt. St. Helens virtually exploded under the pressure of gas buildup, spewing mainly hot rock and ash causing mudflows which blocked rivers and caused flooding far away from the actual volcano peak.