igneous rocks by. group 1 jackie, andrew, brittany, and jessica
TRANSCRIPT
Igneous Rocks
By. Group 1 Jackie, Andrew, Brittany, and Jessica.
What is an Igneous Rock?
• An Igneous Rock are one of the three main rock types. Rocks that form when molten cools and crystallizes.
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Igneous Rock Facts
• Igneous Rocks make up approximately 90% of the upper part of the earths crust, but their great abundance is hidden on the earth’s surface by a relatively thin but widespread layer of sedimentary and metamorphic rocks.
Classifying Igneous Rocks• Igneous rocks are based on mineral
composition (Color), and texture (Crystal Size).
• Differences in magma composition can be observed in the rocks that form when the magma cools and crystallizes.
• Texture is used to subdivide igneous rocks into four groups Glassy, Fine-grained, Coarse-grained, and Very coarse-grained.
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Mineral Composition
Rock type can be determined by estimating the relative percentages of minerals in the rocks.
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Intrusive Rocks• An intrusive igneous rock is when magma rocks is underground, cools and hardens.
• Intrusive igneous rocks form in magma chambers that are deep underground.
• Many kilometers below the Earth surface, molten rock called magma flows into cracks or underground chambers.
• There, the magma sits, cooling very slowly over thousands to millions of years. As it cools, element combine to form common silicate minerals, the building blocks of igneous rocks.
• The mineral crystals within them are large enough to see without a microscope.
• There are many different types of intrusive igneous rocks but granite is the most common type.
Extrusive Rocks
• Extrusive igneous rock forms when molten rock reaches the earth's surface and cools. Air and moisture cool the lava rapidly.
• We can see holes left in the rock where the bubbles of gas were located. These rocks are also known as vesicular rocks.
Vesicular Rocks
• Magma contains dissolved gases that escape when pressure on the magma lessens.
• The holes in the rocks are called vesicles.
• Example Pumice-QuickTime™ and a
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