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Igneous Rocks

Igneous Rocks. Igneous – “FIRE ROCKS”. From red-hot magma…. Extrusive Igneous Rocks. form when lava erupts from a volcano or “bubbles up” from tectonic plates moving apart - onto Earth’s surface. Ex: Basalt – the most common extrusive rock on Earth; forms most of Earth’s ocean floor.

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Igneous Rocks

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  1. Igneous Rocks Igneous – “FIRE ROCKS” From red-hot magma…

  2. Extrusive Igneous Rocks form when lava erupts from a volcano or “bubbles up” from tectonic plates moving apart - onto Earth’s surface. Ex: Basalt – the most common extrusive rock on Earth; forms most of Earth’s ocean floor. Ex: Obsidian – black volcanic glass

  3. Igneous Rocks • Earth's Most Abundant Bedrock: Basalt Basalt forms more of Earth's surface than any other rock type. Most areas in ocean basins are basalt. May be on land from lava flows, too.

  4. Igneous Rock - Obsidian Obsidian was used to make knives, arrow heads, spear points, scrapers and many other weapons and tools

  5. How igneous rocks form… Extrusive When a volcano erupts or when magma bubbles to the surface Intrusive when magma cools slowly inside earth

  6. Intrusive Igneous Rocks • forms when magma hardens beneath Earth’s surface (INSIDE). Ex: Granite – the most abundantintrusive rock on Earth’s continents. Forms the core of many mountain ranges. Ex: Porphyry- looks like jello w/fruit inside it

  7. Intrusive Igneous Rocks • Granite is used to make many objects Granite is also well-known from its many world-famous natural exposures. These include: Stone Mountain, GA; Mount Rushmore, SD

  8. Intrusive Igneous Rock Porphyry—mixed texture (some large and some small grains)

  9. Igneous Rocks Texture – fine grained Rapidly cooling lava forms a fine-grained rock with small crystals. Ex: Basalt - crystals too small to be seen without a microscope. Ex: Obsidian –smooth, shiny texture like thick glass & cooled without forming crystals “Volcanic Glass”

  10. Igneous Rocks • Obsidian Obsidian on the side of a volcano

  11. Igneous Rocks Texture: coarse-grained Slowly cooling magma forms coarse-grained rock with large crystals • Ex: granite and porphyry

  12. Igneous Rocks – Mineral Composition Felsic: When magma is high in silica light-colored rocks form - like granite. Mafic: When lava is low in silica dark-colored rocks form - like basalt

  13. High Silica vs. Low Silica Felsic vs. Mafic

  14. Uses of Igneous Rock Granite – Statues, Bridges and old public buildings, Paving streets with cobblestone, floors, kitchen countertops (thin polished sheets of Granite)

  15. Uses of Igneous Rock Basalt - Gravel for construction Obsidian - Sharp tools for cutting and scraping (Native Am!), Starting vegetable gardens (fertilizer) – it’s called Perlite, which is formed from heating Obsidian

  16. Pumice is cool! It can float! • Pumice – used for cleaning and polishing

  17. Uses of Igneous Rock • Statues, Public Buildings - Granite

  18. Uses of Igneous Rocks • Cobblestone streets, kitchen countertops – Granite

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