Geology

A:

The specific type of rock that forms when magma cools at the Earth's surface is extrusive igneous rock. Igneous rock forms when magma cools, but where the magma cools determines the type of igneous rock that forms. Igneous rock gets its name from the Greek word for fire and is so called due to the extremely hot liquid from which the rocks originate.

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  • What Is the Parent Rock of Gneiss?

    Q: What Is the Parent Rock of Gneiss?

    A: Possible parent rocks of gneiss are granite, shale, gabbro or diorite. Some rocks metamorphose, or change, from one particular kind of rock, but gneiss forms from one of several types. Another name for the parent rock is the protolith.
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  • Where Do Crystals Grow?

    Q: Where Do Crystals Grow?

    A: Mineral crystals form at the surface and deep within the Earth. They grow from vapors that contain plenty of mineral components. Many crystals form in volcanic locations where hot gases encounter cool temperatures.
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  • What Is Clay Soil?

    Q: What Is Clay Soil?

    A: Clay soil is composed of tiny particles that are hard and able to become easily compacted. This compaction makes it difficult to plant or even shovel within the soil.
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  • How Is a Plateau Formed?

    Q: How Is a Plateau Formed?

    A: A plateau is formed by a process of geological uplift, either due to the collision of continental plates, pressure from magma below or the burial of land by volcanic lava and ash flows, resulting in a high, flat surface. These are very similar to processes that give rise to mountains and mountain ranges. The only major difference is that a plateau is flat while mountains are peaked.
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  • Where Can You Find Geodes?

    Q: Where Can You Find Geodes?

    A: Geodes are mostly found in deserts, volcanic ash beds and areas with limestone throughout the world. In the United States, common geode sites include Arizona, California, Iowa, Nevada and Utah. The most abundant geode sites in California are Riverside and Imperial counties.
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  • Is Salt a Non-Renewable Resource?

    Q: Is Salt a Non-Renewable Resource?

    A: Salt, or sodium chloride, is a non-renewable resource. A resource is defined as renewable only if it is self-replenishing. While new salt is being formed by natural processes in the earth, the timescale for that formation is too vast for salt to be considered self-replenishing in terms of human use.
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  • What Is the Fossil Record?

    Q: What Is the Fossil Record?

    A: The fossil record refers to the collection of physical and research evidence that paleontologists and geologists have used to prove the veracity of evolutionary theory. The physical evidence in the fossil record comes from fossilized remains of prehistoric animals.
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  • What Are Igneous Rocks Used For?

    Q: What Are Igneous Rocks Used For?

    A: Igneous rocks are often used for construction because of their durability. Igneous rocks can also be separated to access the various valuable metals and minerals inside them. Igneous rocks form as magma comes to or near the surface of the Earth; cooling and hardening because of its distance from the inner parts of the Earth where magma forms.
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  • Why Is Limestone Important?

    Q: Why Is Limestone Important?

    A: According to the U.S. General Services Administration, limestone is important because it is widely used in architectural applications for walls, decorative trim and veneer. It is less commonly used in making sculptures because of its porosity and softness.
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  • How Do Petrified Fossils Form?

    Q: How Do Petrified Fossils Form?

    A: According to the Oxford University Museum of Natural History, petrified fossils form when mineral deposits replace the bones of dead creatures inside hardened sediment. Over time, these deposits completely replace the remains, forming an image of the bones out of solid rock.
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  • What Is Dry Lava Called?

    Q: What Is Dry Lava Called?

    A: Dry lava is called igneous rock. The superheated molten rock that reaches the surface in an eruption is called lava, and lava may flow for miles before cooling.
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  • Where Is Coal Found?

    Q: Where Is Coal Found?

    A: Coal reserves exist in every country in the world and on every continent except Antarctica. According to the World Coal Association, there are enough coal reserves to meet current demand for 112 years, but only enough oil and gas reserves to meet current demand for the next 46 and 54 years, respectively.
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  • How Is Sulfur Mined?

    Q: How Is Sulfur Mined?

    A: At the beginning of the 1900s, the Frasch process of mining sulfur became the most popular way of extracting it. However, by the end of the 1900s, most sulfur has been manufactured by recovering it from petroleum and gas.
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  • What Is a Mineral Resource?

    Q: What Is a Mineral Resource?

    A: A mineral resource is the concentration of materials that are of economic interest in or on the crust of the Earth. Almost all minerals found on Earth are used in one way or another for economic benefit. Examples of minerals include gold, gravel, sand, aluminum, copper, limestone, clay and diamond.
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  • How Are Minerals Formed?

    Q: How Are Minerals Formed?

    A: Minerals are formed under a variety of conditions, including when molten materials cool, when liquids evaporate or cool and under high temperatures and pressures. Minerals are found in the earth's crust and mantle, and many were created when feldspar and quartz reacted with other materials during the formation of the planet.
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  • What Is a Mine-Cut Diamond?

    Q: What Is a Mine-Cut Diamond?

    A: Mine-cut diamonds are typically square or slightly oval and have a deeper crown and pavilion, or top and bottom, than modern stones. "Mine cut" does not refer to the place the diamond was faceted, but rather to its overall shape and brilliance.
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  • Does Sand Dissolve in Water?

    Q: Does Sand Dissolve in Water?

    A: Sand does not dissolve in water. Sand is mostly made of fine quartz, which does not dissolve in water. Sand does dissolve in certain hot acids.
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  • Where Do Rocks Come From?

    Q: Where Do Rocks Come From?

    A: Rocks come from magma, which is the molten material found within the earth. When magma cools, either above or below the earth's surface, it crystallizes and forms the igneous rocks that can later be changed into metamorphic or sedimentary rocks. Magma, which can be considered molten rock, is referred to as lava when it reaches the earth's surface.
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  • How Is Quartz Mined?

    Q: How Is Quartz Mined?

    A: The Encyclopedia of Arkansas explains that commercial mining of quartz is rare and occasionally consists of the use of explosives to first expose the quartz, followed by the operation of small hand tools such as chisels and rock picks to extract portions of the mineral from a quarry. Quartz is quite sensitive to temperature changes, so miners prefer not to use explosives unless absolutely necessary.
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  • What Is Absolute Dating?

    Q: What Is Absolute Dating?

    A: Absolute dating is a method of determining the specific date of a paleontological or archaeological artifact or location based on a specific time scale or calendar. Scientists base absolute dating on measurable physical or chemical changes or on written records of events.
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  • What Is Exfoliation Geology?

    Q: What Is Exfoliation Geology?

    A: Exfoliation geology is a type of rock weathering where the rock's layers peel off in whole sheets instead of grain by grain. Large-scale exfoliation occurs due to the mechanics of gravity on a curved surface, while small-scale exfoliation is due to chemical weathering.
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