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Science Notes 02-06-12 I. Section 1: Rocks A. Rock – is a mixture of minerals, volcanic glass, organic matter, and/or other materials. B. There are 3 basic types of rock, including igneous, sedimentary, metamorphic rock. 1. Igneous rock a. The word igneous comes from the Latin word igneus, which means fire. An erupting volcano releases lava b. Igneous rock is formed when magma or lava, from a volcano, cool down and becomes a solid. Image 1 of 2: As lava cools it begins to solidify into igneous rock Image 2 of 2 c. Magma trapped below the Earth’s surface can cool and become intrusive igneous rock. d. Magma cooling near the Earth’s surface or on the surface (as lava) can cool and become extrusive igneous rock. extrusive vs. intrusive igneous rock* e. Crystal size, large or small, can help identify an igneous rock as intrusive or extrusive. f. Some igneous rocks have holes that form from the release of trapped hot gases as the rock is forming from magma or lava. g. The 3 types of igneous rock include: i. Basaltic igneous rock- is dark-colored and dense. 1. Contain iron and magnesium but very little silica 2. Basaltic lava flows freely from a volcano ii. Granitic igneous rock- is lower in density and of lighter color. 1. Contain more silica and less iron and magnesium 2. Granitic lava is thick and stiff iii. Andesitic igneous rock- has a more balanced composition of minerals and density compared to basaltic and granitic igneous rock. 2. Sedimentary rock a. Sedimentary rock is rock that forms from sediments. b. Sediments are the small fragments of rock, mineral grains, and bits of plant/ animal remains that eventually settle to the bottom. i. Sediments are moved or taken to the bottom of the ocean or canyons by wind, water (rain), or gravity. ii. Once there, pressure pushes these sediments together to form sedimentary rock. c. Sedimentary rocks are classified by what they are made of and how they formed. 1. Detrital sedimentary rocks- are made from broken fragments of other rocks. a. When sediments stick together because of pressure, compaction occurs. 2. Chemical sedimentary rocks- are made from rocks that are formed mostly by minerals that grew out of a solution. 3. Organic sedimentary rocks- are formed from the remains of once living plants or animals. a. For example: Chalk is a type of organic sedimentary rock because it is made from the microscopic calcite-shell remains of animals. These sea shells come from sea animals After many years, sea shells get broken down into microscopic pieces. These very small pieces become pressured together to become organic sedimentary rock. This piece of chalk is made from the microscopic calcite-shell remains of sea animals. Chalk, therefore, comes from organic sedimentary rock. More examples of sedimentary rock Image 3 of 4: sedimentary rock (sandstone) Image 4 of 4: Sedimentary rock (notice the different layers of rock) Q: What type of rock is this and how do you know? 3. Metamorphic rock - is rock that forms from heat and pressure. a. The semiotics (meaning) of the word metamorphic: i. Meta means change, and morph means shape. b. Classification of metamorphic rock by composition and texture: i. Foliated texture- mineral grains flatten and line up in parallel layers. Metamorphic rock (Foliated Gneiss) ii. Nonfoliated texture- mineral grains grow and rearrange but do not form layers. Nonfoliated Metamorphic rock (Nonfoliated Marble) Nonfoliated Metamorphic rock (Hornfels) II. Section 2: The Rock Cycle: A. The Rock Cycle – is a model that shows the processes that change rock from one form to another. B. Law of Conservation of Matter- is a law that states that matter cannot be created or destroyed. i. Rocks are matter; therefore, the rock cycle never destroys the elements of rock but instead redistributes them. ii. James Hutton, MD., recognized the rock cycle in 1788 by observing Siccar Point, Scotland. 1. He is considered the father of modern geology. Geologist James Hutton posing for a painting A picture of Siccar Point in Scotland – notice the layers of different rock Pic 2: Siccar point in Scotland *End Notes*