2 Igneous Rocks Form from lava or magma Made of mineral crystals Classified according to:OriginTextureMineral Composition
3 Origin of Igneous Rocks Classified according to where they formed.IntrusiveExtrusive
4 Origin of Igneous Rocks IntrusiveForms when magma hardens beneath the Earth’s surface.GraniteMakes up most of the continental crust.
5 Origin of Igneous Rocks ExtrusiveForms from lava that erupted onto Earth’s surface.BasaltForms much of the ocean crust.
6 Which is a way to identify if a rock is Igneous? StreakBOriginCSolidDHardness
7 Igneous Rock Textures Slowly cooling, large crystals Example: Granite Coarse GrainedSlowly cooling, large crystalsExample: GraniteFine GrainedLava cools quicklyForms smaller crystals.PorphyriticBoth textures – large AND small crystals.Cools slowly, then rapidly.No CrystalsRock cools too quickly for crystals to form.
8 What is a Crystal?A solid in which the atoms are arranged in a pattern that repeats again and again.
9 Igneous Rock TexturesDepends on the size and shape of it’s mineral crystals.Coarse GrainedPorphyriticFine GrainedNo Crystals
10 In your tray, what is the texture of sample… Coarse-grainedBFine-grainedCPorphyriticDNo visible crystals
11 Mineral CompositionMost of Earth’s rocks contain silica (silicon dioxide, SiO2)High Silica (Felsic)Forms light colored rocks.GraniteDark to light gray, red and pink.Low Silica (Mafic)Forms dark colored rocks.BasaltContains dark colored minerals. No quartz.
12 Igneous Rock Chart Low Density High Felsic (High) Silica Mafic (low) OriginIntrusive(Magma)Coarse GrainedGraniteContinentalCrustGabbroBothPorphyriticLarge crystals withsmall crystalsScattered on top.Extrusive(Lava)Fine- GrainedRhyoliteBasaltOceanNo CrystalsPumiceObsidian
14 Igneous rocks are useful because they are hard, durable and dense Uses of Igneous RocksGranite - building materialsObsidian - sharp toolsBasalt - gravel, constructionPumice - used for cleaning and polishingIgneous rocks are useful because they are hard, durable and dense
15 Class Work Examine 5 Igneous Rocks and write down their texture (Fine-grain, Coarse-grain, Porphyritic, No Grain)Read the textbook, pages 78-81Answer Questions 1 – 4 on page