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Rocks. What is a rock? Which of the following are rocks: Ice Water Coal Dead Plant Table Salt Processed Sugar Mined Diamond Artificial Diamond.

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Presentation on theme: "Rocks. What is a rock? Which of the following are rocks: Ice Water Coal Dead Plant Table Salt Processed Sugar Mined Diamond Artificial Diamond."— Presentation transcript:

1 Rocks

2 What is a rock? Which of the following are rocks: Ice Water Coal Dead Plant Table Salt Processed Sugar Mined Diamond Artificial Diamond

3 Definition Solid Naturally occurring Combinations (mixtures!) Minerals and/or organic materials

4 List RocksNot Rocks IceWater CoalDead Plant SaltSugar Mined diamondsArtificial Diamonds

5 How are igneous rocks formed? Are made from magma that has been cooled down from liquid to solid

6 Difference between magma and lava?

7 Answer Magma is molten rock inside the Earth Lava is molten rock on the surface of the Earth

8 Rock Characteristics Use to tell history, origin of the rock Did it form inside or on the surface of Earth How long did it take to form?

9 Rock Characteristics Rock Texture: Relates to size of the mineral crystals. The size of the crystal indicates the amount of time it takes to cool down and form a solid object. The larger the crystals, the longer the time of formation Types of textures- Coarse Grained: Large crystals Fine Grained : Small crystals. Will usually not be able to see crystals without microscope

10 Other texture types Glassy: No crystals, even under a microscope – Indicates very rapid cooling of lava (seconds) Vesicular: Rocks with holes – Holes indicate escape of gases during rapid cooling

11 Color (2 nd Characteristic) Color indicates composition of the rock Light colored rocks: indicate rocks with high concentrations of Si, O, K and Na White, pinks and gray – These rocks have a Felsic composition – Formed within continents

12 Color Dark colored: Color dominated by dark greens and black These rocks have high concentrations or Fe, Mg and Ca These rocks have a mafic composition These rocks are formed within oceans

13 Nothing is black or white… A lot of rocks are combinations of felsic and mafic materials Color will be medium dark (usually dark gray) These have an intermediate composition

14 Felsic Rocks

15 Mafic Rocks

16 Density (3 rd Characteristic) Mafic rocks are generally more dense than Felsic rocks

17 Rock Names Match the name to your rock sample based on your observations Basalt- fine grained, mafic Gabbro- coarse grained, mafic Granite- coarse grained, felsic Obsidian- glassy, mafic Pumice- vesicular (very small holes), felsic Tuff- fine grained, felsic Scoria – vesicular (larger holes), mafic

18 Types of volcanic rocks Obsidian: Mafic, Glass, no crystals, instant solid Tuff, pumice: Felsic, Tiny crystals, with holes, quick solidification Basalt: Mafic, tiny crystals, lava solidification Granite, Felsic, large crystals, magma solidification without exposure to air

19 What do the rocks tell about its history… Basalt, obsidian, pumice, tuff and scoria are examples of extrusive igneous rocks. These rocks were created from the material extruded from an volcanic eruption In general, extrusive rocks have no crystals or very small crystals: short cooling time

20 Gabbro,and granite are examples of intrusive igneous rocks Formed when magma slowing cools inside the earth before exposed through erosion Formed when magma is given a chance to slowly cool over millions of years, without being exposed to the surface of the earth

21 Why do intrusive rocks grow such big crystals? Because the rocks in the interior of the Earth are poor conductors of heat, it takes a long time for the hot magma to be cooled. Thus, the intrusive igneous rocks have a coarse- grained texture due to their slow cooling.

22 Devils tower


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