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Igneous Rocks Rocks Brain-Pop. Igneous Rocks Rocks that form when natural, molten rock- forming material cools and turns into a solid.

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Presentation on theme: "Igneous Rocks Rocks Brain-Pop. Igneous Rocks Rocks that form when natural, molten rock- forming material cools and turns into a solid."— Presentation transcript:

1 Igneous Rocks Rocks Brain-Pop

2 Igneous Rocks Rocks that form when natural, molten rock- forming material cools and turns into a solid

3 Igneous Rock Formation Video

4 Liquid (molten) rocks Lava – On the Earth’s surface (Extrusive) Magma – Beneath the Earth’s surface (Intrusive)

5 Formation Cooling Rates Animation Solidification – the change from a liquid to a solid Crystallization – molten magma or lava cools and form solid rocks composed of intergrown mineral crystals

6 Intrusive Igneous Rocks : forms underground magma never reaches the surface cools slowly form large crystals medium to coarse grained texture Get exposed at the surface only when rock is uplifted and exposed

7 Intrusive Igneous Rocks Video

8 Extrusive Igneous Rocks: Forms on the surface Lava comes out of a volcano cools rapidly forms small crystals glassy or fine-grained Covers the surface as lava flows or pyroclastic debris

9 Extrusive Igneous Rocks Video

10 CRYSTAL SIZE VS. COOLING TIME CrystalCrystal Cooling TIME SIZESIZE As cooling time increases, crystal size increases.

11 Felsic Rich in: Silica Aluminum Potassium Feldspar Quartz Felsic Rich in: Silica Aluminum Potassium Feldspar Quartz Mafic Rich in: Iron Pyroxene Olivine Mafic Rich in: Iron Pyroxene Olivine They are classified according to their chemical composition and texture Classification of Igneous Rocks: The % of different minerals affect the color of the rock More silica the lighter the rock, less silica the darker More Iron the darker the rock, less Iron the lighter

12 Classify the following rocks as either: Extrusive or Intrusive Mafic or Felsic Intrusive + Mafic = GabbroExtrusive + Mafic = Basalt

13 Vesicles (Vesicular) As lava rises and cools to form extrusive igneous rock, Pressure drops which causes the gases that are in the lava to expand. These gases form vesicles (cavities) which are the remains of gas bubbles. Intrusive rocks rarely contain vesicles because they are formed at depth where high pressure stops the gases from expanding.

14 Vesicular Rocks - Pumice

15 Compare Granite and Basalt Granite - Intrusive (large crystals) Felsic (Light In Color) Basalt - Extrusive (Small Crystals) Mafic (Dark In Color)

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17 Crystallization: Crystal Size Animation Magma is a mixture of different substances. They all have different melting points. So as magma cools, some substances will form crystals before other substances. They have a head start in growth and tend to be bigger. If the magma already has crystals present in it and then is cooled rapidly then you will see large crystals embedded in finer-grained material. This is called a porphyritic texture

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21 Basaltic lava in Hawaii Top: Basaltic lava flow Bottom: Slow moving lava Top: Basaltic lava flow Bottom: Slow moving lava

22 Magma & Lava Video

23 Mt. St. Helens Pre eruption Post eruption (May 1980)

24 Igneous Rock Review 1. What is the difference between magma and lava? 2. What are the two main types of igneous rocks? 3. How can you tell them apart? 4. Why is it not common for Intrusive rocks to have vesicles? Vocabulary: magma, lava, intrusive, extrusive, vesicles, felsic, mafic


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