2Igneous Rocks Form from lava or magma Made of mineral crystals Classified according to:OriginTextureMineral Composition
3Origin of Igneous Rocks Classified according to where they formed.IntrusiveExtrusive
4Origin of Igneous Rocks IntrusiveForms when magma hardens beneath the Earth’s surface.GraniteMakes up most of the continental crust.
5Origin of Igneous Rocks ExtrusiveForms from lava that erupted onto Earth’s surface.BasaltForms much of the ocean crust.
6Which is a way to identify if a rock is Igneous? StreakBOriginCSolidDHardness
7Igneous 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.
8What is a Crystal?A solid in which the atoms are arranged in a pattern that repeats again and again.
9Igneous Rock TexturesDepends on the size and shape of it’s mineral crystals.Coarse GrainedPorphyriticFine GrainedNo Crystals
10In your tray, what is the texture of sample… Coarse-grainedBFine-grainedCPorphyriticDNo visible crystals
11Mineral 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.
12Igneous Rock Chart Low Density High Felsic (High) Silica Mafic (low) OriginIntrusive(Magma)Coarse GrainedGraniteContinentalCrustGabbroBothPorphyriticLarge crystals withsmall crystalsScattered on top.Extrusive(Lava)Fine- GrainedRhyoliteBasaltOceanNo CrystalsPumiceObsidian
14Igneous 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
15Class 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