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1.USGS, Science For A Changing World (n.d) What are metamorphic rocks? Accessed 18 August 2019. Available from: https://www.usgs.gov

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Rocks are slowly but continuously changing in something known as the 'Rock cycle.' This cycle begins with magma, or hot, molten rock deep beneath the Earth's surface, this magma then cools down and forms igneous rocks. These rocks begin to erode, and weather, or better said, break down into smaller pieces because of the wind, water and other forces. The small fragments of rock are then passed away as sediment and drenched into the water to form deposit layers, which eventually become sedimentary rock. Then some sedimentary rocks are forced underneath the surface due to tectonic activity, where they get exposed to heat and pressure, transforming into metamorphic rocks, and if the rocks are buried even more in-depth, they may even melt into magma and start the cycle all over again. As seen in the picture on the left, sedimentary and metamorphic rocks can erode into sediments, and igneous rock can become metamorphic rocks or lava, but one way or another, rocks all over the world are always changing from one form into another.

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What is an example of metamorphic rocks?

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What is an example of metamorphic rocks?

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Marble is the metamorphic state of limestone; marble is formed when high heat and pressure is implied on limestone, sometimes by contact metamorphism, when hot bodies of magma heat adjacent limestone or dolostone. This process causes the minerals; micas, quartz, pyrite, iron oxides, and graphite to crystallize and form larger crystals that can be seen by the naked eye. Marble mainly gets used as building materials as it is easy to cut and shape. Marble is used in the making of bathroom tubs, sinks, monuments, roads, buildings, sculptures, paving and other projects that require durable materials. Marble has a hardness of three on the Mohs scale, which tells us that it is smoothly curved and shaped. When marble gets crushed into its powered state, its white streak, it gets used as a colouring agent in plastic, cosmetics, paper, putty and other products that have an intense white colour. The colour of the marble rock can change from white to light brown, bluish, pink, grey, yellow and sometimes even black.

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What are some characteristics for Metamorphic rocks?

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What are some characteristics for Metamorphic rocks?

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Critical features like hardness, strata and cleavage all classify metamorphic rocks. The first feature of metamorphic rocks is the hardness. Hardness is how hard an object is, and in this case, that object is a rock. The Mohs scale usually measures the hardness of rocks, a scale that tests the resilience of materials by scratching one another. This scale tends to start at one, meaning its hardness is very low and can go up to ten, tell us that its harness is quite significant, all depending on the rock itself. Metamorphic rocks are known to be the hardest rocks in the world, and commonly score an average of 6 to 7 on the Mohs scale; that is because of the constant high pressure this rock type receives, the constant bending, folding, crushing, flattening and shearing can cause the particles in this rock to move in closer together and result in a strong base. The second feature of metamorphic rocks is the strata. Strata meaning layers, the layers in metamorphic rocks are most of the time seen as inline and overlaying. These layers form from the enormous amount of pressure that this rock receives; it pushes and lines up all the minerals and results in an overlaying, orderly pattern. The third feature of metamorphic rocks is the cleavage. Cleavage of fracture refers to the breakage of rocks either with ease or difficulties. If the rock breaks easily along the cleavage planes, it is considered as perfect cleavage, and if the rock does not break at all or only with difficulties, it is called imperfect cleavage. Metamorphic rocks are divided into two categories, Foliates and Non-foliates. Foliate meaning sheets of paper in Latin, this group refers to the ones who can split among their cleavage lines and break into thin sheets, like slate. Non-foliates are the opposite; they have no cleavage at all; they do not break with difficulties like Marble and Quartzite. Metamorphic rocks tend to switch around, there is a hand full of rocks that have perfect cleavage, and imperfect cleavage but most commonly these rocks have perfect cleavage; this is from all the banding that flattens the rock and squishes all the layers together to create clean breakage lines that make it easier to break the rock. Those were the three critical features that classify metamorphic rocks.

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What is an example of Sedimentary rocks?

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What is an example of Sedimentary rocks?

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Coquina is a sedimentary rock; this rock is composed almost entirely of sand-size fossil debris. This debris is mostly made of shells fragments that came off mollusc and gastropods. Sometimes, brachiopod, trilobite, coral, ostracod and other invertebrate shells are examined in this rock aswell. All of these shells and fossil debris are lightly cemented together by silt or clay. Now, Coquina is commonly used as a material for building constructions, which was influenced by actions of the Spaniards about a thousand of years ago, when they built a fort on the coast of Matanzas Bay at St. Augustine, Florida out of this material to protect themselves from the cannons, and brilliantly it worked; the fort is still standing today. The hardness of this rock is said to be a shocking number of 2 on the Mohs scale, even though the first building to use this is still standing and alive after all of those attacks from the 1700s. Coquina varies widely in colour from white, yellow, and pink to blue and mauve; this is because different coloured shells and fossils get cemented together to create this rock; but when this rock get powered or crushed, the streak colour is just naturally white.

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Obsidian is an extrusive igneous rock; which means this rock has chilled on or near the Earth's surface; suggesting that the lava automatically cooled down because of the Earth's atmosphere, giving the obsidian a fine-grains and no time to form crystals, meaning it has not got crystals, but instead a naturally glassy texture with the hardness of 5.5 on the Mohs scale. Obsidian is nowadays commonly used in jewellery, mirrors, cutting tools, and modern surgery equipment like being cut into blades that are used in the most precise surgeries. Obsidian is known for its cleavage or fracture, as when it tends to break it leaves behind a smooth, ridged, curvy fracture on its surface; this is what they call a distinct conchoidal fracture. The colours of the obsidian rock can change from deep black to dark brown and tan. It can rarely change to green, blue, red, orange, and yellow; this all modifies because of the chemical installability of this rock. Streak is the colour of the rock when it gets crushed or powered; the streak of this rock is white.

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What are some characteristics of Igneous rocks?

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What are some characteristics of Igneous rocks?

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Igneous rocks consist of three principal components such as magnetism, crystallization, and texture. The first principle of Igneous rocks is the magnetism. Magnetism is the state of being magnetic, and igneous rocks are incredibly magnetic. Igneous rock always starts as magma or lava before solidifying. From the magma, iron bears being to form and act like tiny magnets. These magnetic minerals then float into the solidifying mixture and in line with the magnetic felids of the Earth, making the rock magnetic. The alinement of these atoms could potentially line up the atoms of nearby metal objects, as the fields from the igneous rock can strangely become dominant. Igneous rocks can attract several metals like gold, silver, nickel and other metals. The second principle of Igneous rocks is crystallization. Crystallization is when atoms or molecules form and solidify into a crystal structure. Igneous rocks can have crystals; small, large and sometimes no crystals at all; this depends on where exactly the lava cools down and solidifies. If this rock is extrusive, meaning it cools down above or near the Earth's surface, the rock will consist of extremely tiny crystals or none at all because of the atmosphere, as it immediately cooling down the lava before any major formations can occur. If the rock is intrusive, meaning it cools inside the Earth's surface, the rock will consist of large crystals as its exposure to air is limited; the lava would be cooling in an air-tight place, which gives it more time to formate into extended sizes of crystals and solidify. Igneous rocks containing some or none crystals affects its texture, which perfectly transfers into our third principle, texture. Igneous rocks can have many textures, depending on, again, where it forms. If the rock forms underground, it is going to have course-grains, which means the texture is going to be rough and crystalized, like granite. If the rock forms on the surface, it is going to have fine-grains and no crystals, which means the texture is going to be smooth and give off a glassy look, like obsidian. Sometimes, the rocks that cool on the surface can get gas-bubbles trapped inside, which gives the rock a spongy look with a rough feel to it. Those were the three principal components of igneous rocks.

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What are some characteristics of Sedimentary rocks?

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What are some characteristics of Sedimentary rocks?

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Three principal characteristics can be used to identify sedimentary rocks; these characteristics are strata, organic compaction and grain size. The first characteristic of sedimentary rocks is the strata. Strata is a word describing the layers in rocks. In terms of sedimentary rock, these layers typically are seen as long, parallel bands of different coloured sediment structures that lay on top of each other. The arrangement of different alined sediments usually occurs from the movement of loose particles by natural processes like water and wind. The thickness of each stratum can vary from a few millimetres to kilometres; this depends on the size, weight and shape of the compacted specks. These layers can compose of compacted organic materials; which leads us into our second characteristic, organic material. Organic materials are the living or once was living matter of animal and plant remainings that have survived and stayed on this Earth for a long time. In this rock, organic matter can get gathered by natural processes and pile up into the strata of sedimentary rocks along with sediments, that also get clayed and cemented into one form. These strata can include bones, plant roots, shells, soils and other forms of organic material, which results in the creation of many frequently used fossils like coal. Our last characteristic for sedimentary rocks is the grain size. The grain size is the diameter of individual grains or sediments in a rock. Sedimentary rocks tend to have an indecisive grain size; sometimes this rock can contain fine grains and other times, large grains. The inclusion of sediments causes this dramatic change; as sediments with different sizes tend to group and stick together, constructing this rock with multiple grains of different size; but not all sedimentary rocks have this characteristic, even though it is quite common, there are some rocks like limestone that have the same sized grains though out the whole rock. Those were the three characteristics that can be used to identify sedimentary rocks.

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Extrusive, or volcanic, igneous rocks are produced when magma exits and cools above or near the Earth's surface. These rocks form when hot spots and volcanic eruptions occur. The magma called lava cools and solidifies almost instantly after being exposed to the relatively cold temperature of the atmosphere; this can be called quick cooling. Quick cooling means that mineral crystals do not have much time to grow, and because of that, these rocks have very fine-grains and a glassy look. Hot gas bubbles often get trapped inside the quenched lava, giving extrusive rocks a bubbly, vesicular texture.

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Intrusive, or plutonic, igneous rocks form when magmas trapped deep inside the Earth, the magma then cools down underneath the Earth's crust to form that rock type. It can take up to thousands and millions of years for this rock to fully solidify; this can also identify as slow cooling. Slow cooling means that the individual mineral grains have a long time to grow, which usually result in relatively huge rocks that consist of large course-grains and crystals, with phaneritic textures. The word "phaneritic" means large, identifiable crystals of equal sizes that are visible to the naked eye.

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All metamorphic rocks start off as igneous or sedimentary rocks, but as chemical changes occur to their igneous or sedimentary state, they begin to change, which is what the word metamorphism means; to change form. Metamorphic rocks start to change from their original state when high heat, high pressure, or hot mineral-rich fluids are implied onto them and cause physical and chemical changes; igneous and sedimentary rocks can change from these too. Some examples of metamorphic rocks are Banded iron formation (BIF), gneiss, slate, marble and schist.

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Igneous meaning fire in Greek, Igneous rocks form when hot, molten rock, or better known as magma crystallises and solidifies. The magma originates deep within the Earth near active plate boundaries or hot spots and then rises toward the surface to form; making these rocks volcanic. These can sometimes bear precious metals like gold, silver, nickel and copper. Igneous rocks are split into two separate classes, intrusive or extrusive, depending upon where the molten rock solidifies.

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Sedimentary rocks form from pre-existing rocks or pieces of once-living organisms. They develop from deposits that accumulate on the Earth's surface by cementing together. These rocks often have distinctive layering or bedding; like limestone and sandstone. Interestingly, sedimentary rocks often contain fossils or fossilised animal tracks because of the gathering of once-living organisms.