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Igneous Rocks. What is an igneous rock? Born from fire Any rock that forms from magma or lava Most contain mineral crystals.

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Presentation on theme: "Igneous Rocks. What is an igneous rock? Born from fire Any rock that forms from magma or lava Most contain mineral crystals."— Presentation transcript:

1 Igneous Rocks

2 What is an igneous rock? Born from fire Any rock that forms from magma or lava Most contain mineral crystals


4 Characteristics of Igneous Rocks Classified according to their… –Origin –Texture –Mineral composition

5 Origin Extrusive Rock- formed from lava that erupted onto Earth’s surface (ex. Basalt) Intrusive Rock- igneous rock that formed when magma hardened beneath Earth’s surface (ex. Granite)

6 Basalt Granite

7 Texture Fine-grained Coarse-grained Glassy porphyritic

8 Fine-Grained Rapid cooling lava Small crystals Extrusive rocks

9 Coarse-Grained Slow cooling magma Large crystals Intrusive rocks

10 Porphyritic Large crystals scattered on a background of much smaller crystals Intrusive rocks cool in 2 stages- rate of cooling is changed from slow to fast

11 What is the texture of the rock? Flow banding

12 Mineral Composition Lava that is low in silica- dark colored rocks Magma high in silica- light colored rock

13 Uses of Igneous Rocks Igneous rocks are hard, dense, and durable so they are used for –Tools –Building materials Granite- long history of building material

14 Sedimentary Rocks

15 What is a sedimentary rock? Composed of sediments derived from pre-existing rocks or by the crystallization of minerals that were held in solutions Sediment- small, solid pieces of material that come from rocks or living things Can include fossils, leaves, etc.

16 How do the sediments turn into a rock? 1.Erosion 2.Deposition 3.Compaction 4.Cementation

17 Erosion Water, wind, or ice loosen and carry away fragments of rock

18 Deposition That’s when sediments stop traveling by water or wind and settle


20 Compaction Sediments fit loosely Years go by…thick layers build up Layers are heavy and press down Compaction- process that presses sediments together (squeezes)

21 Cementation During compaction…minerals dissolve in water Dissolved minerals crystallize and glue particles of sediments together Whole process: millions of years

22 0604page01.cfm?chapter_no=visualization

23 Types of Sedimentary Rocks Clastic rocks Organic rocks Chemical rocks

24 Clastic Rocks Forms when rock fragments are squeezed together Grouped by size of fragments & of which they are made Ex. shale, sandstone, conglomerate and breccia

25 Shale Forms from tiny particles of clay Thin, flat layers

26 Sandstone Forms from sand Contains holes- can absorb water

27 Conglomerate & Breccia Mixture of rock fragments of different sizes

28 Organic Rocks Remains of plants & animals are deposited in layers Coal and limestone

29 Coal From remains of swampy plants

30 Limestone From hard shells of living things Ex. chalk

31 Chemical Rocks Forms when minerals that are dissolved in a solution crystallize (ex. rock salt)

32 Metamorphic Rocks

33 What is a metamorphic rock? A rock that has changed its form Can change igneous, sedimentary, or other metamorphic rocks

34 How do metamorphic rocks form? Heat and pressure beneath Earth’s surface change rock Its appearance, texture, crystal structure, and mineral content change

35 Formation of Metamorphic Rocks 1.Earth’s plates push rock down toward mantle- HOT! 2.Magma also heats the rock 3.The deeper the rock is buried…the greater the pressure 4.Pressure and heat change minerals

36 Formation of Metamorphic Rocks

37 GRANITE Gneissic granite – separation of dark & light minerals is just beginning Well banded gneiss Granite to Gneiss

38 Classifying Metamorphic Rocks Classify rocks by arrangement of grains that make up the rock Two types: foliated and nonfoliated

39 Foliated Rock Grains arranged in parallel layers Can split apart along the bands

40 Shale to Slate Shale Slate

41 Nonfoliated Rock Mineral grains are arranged randomly Do not split into layers Marble

42 Sandstone to Quartzite

43 Uses of Metamorphic rocks Slate and marble- most useful metamorphic rocks Marbles- buildings and statues Slate- flooring, roofing, chalkboards

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