Geology ( Rocks )

THE STRUCTURE OF THE EARTH CRUST

The majority of research in geology is associated with the study of rock, as rock provides the primary record of the majority of the geologic history of the Earth. There are three major types of rock: igneous, sedimentary, and metamorphic. The rock cycle is an important concept in geology which illustrates the relationships between these three types of rock, and magma. When a rock crystallizes from melt (magma and/or lava), it is an igneous rock. Igneous rock can be weathered and eroded, and then redeposited and lithified into a sedimentary rock, or be turned into a metamorphic rock due to heat and pressure that change the mineral content of the rock which gives it a characteristic fabric. The sedimentary rock can then be subsequently turned into a metamorphic rock due to heat and pressure and is then weathered, eroded, deposited, and lithified, ultimately becoming a sedimentary rock. Sedimentary rock may also be re-eroded and redeposited, and metamorphic rock may also undergo additional metamorphism. All three types of rocks may be re-melted; when this happens, a new magma is formed, from which an igneous rock may once again crystallize.MineralsTo study these three types of rocks, geologists evaluate the minerals that make up the rock. All the colors you see in rocks are the different minerals crystallized within. Each mineral has distinct physical properties and there are multiple tests that a geologist can do to determine each one. The Mineral Identification tests are:

• Luster: Measurement of the amount of light reflected from the surface. Luster is broken up into Metallic and Non-metallic.

• Color: Minerals are grouped by their color. Mostly diagnostic but impurities can change a mineral’s color.

• Streak: Performed by taking a porcelain plate and scratching the mineral on it. The color of the streak can help you name the mineral.

• Hardness: The resistance of a mineral to scratch.

• Breakage Pattern: A mineral can either show fracture or cleavage. Fracture being breakage of uneven surfaces and cleavage being breakage along closely spaced parallel planes.

• Specific Gravity: the weight of a specific volume of a mineral.

• Effervescence: Involves dripping HCL on a mineral to test for fizzing.

• Magnetism: Involves using a magnet to test for magnetism.

• Taste: Minerals can have a distinctive taste like Halite (tastes like salt).

• Smell: Minerals can have a distinctive odor. For example, sulfur smells like rotten egg

Geology (from the Ancient Greek γῆ, gē, i.e. "earth" and -λoγία, -logia, i.e. "study of, discourse"^[1][2]) is an earth science concerned with the solid Earth, the rocks of which it is composed, and the processes by which they change over time. Geology can also refer generally to the study of the solid features of any terrestrial planet (such as the geology of the Moon or Mars).Geology gives insight into the history of the Earth by providing the primary evidence for plate tectonics, the evolutionary history of life, and past climates. Geology is important for mineral and hydrocarbon exploration and exploitation, evaluating water resources, understanding of natural hazards, the remediation of environmental problems, and for providing insights into past climate change. Geology also plays a role in geotechnical engineering and is a major academic discipline.

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