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Igneous Rocks. “Liquid Hot Magma!”. Igneous Rocks. Rocks formed from cooling of lava or magma Lava-Melted rock erupted from volcanoes and deposited on the earth’s surface. Cools quickly. Magma-Melted rock that sits inside the earth in a magma chamber. Cools slowly. Magma Chamber. - PowerPoint PPT Presentation
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Igneous Rocks
“Liquid Hot Magma!”
Igneous Rocks
• Rocks formed from cooling of lava or magma• Lava-Melted rock erupted from volcanoes and
deposited on the earth’s surface. Cools quickly.• Magma-Melted rock that sits inside the earth in a
magma chamber. Cools slowly.
Magma Chamber
Types of Igneous Rocks
• 2 major types: Intrusive and Extrusive• Intrusive igneous rocks cool and harden inside
the earth. • Extrusive igneous rocks cool and harden on
the earth’s surface or outside the earth.
Intrusive Igneous Rocks• Form when magma cools
before reaching the surface. – Cool very slowly– Intrusive igneous rocks have
large, interlocking crystals because they cooled slowly inside the earth.
– Examples are Granite, Gabbro, Diorite, and Unakite (Virginia’s State Rock!)
Unakite
Granite
Extrusive Igneous Rocks• Form when lava erupts and
hardens on the surface. – Cool very quickly– Extrusive igneous rocks have
fine (small) to no crystal grains at all.
– A rock with no visible grains is called a volcanic glass (examples are pumice and obsidian).
– Examples are Obsidian, Pumice, Scoria, Basalt, Tuff, Porphyry (cools inside then erupts), Rhyolite, Andesite.
Rhyolite
Obsidian
Texture of Igneous Rocks
• Grain Size (Glassy, Fine, Medium, Coarse)• Grain Shape (Irregular, Angular)• Sorting:
– Glassy: Looks like glass (Obsidian, Pumice)– Aphanitic: Can’t see crystals (Scoria, Tuff)– Porphyritic: Large crystals in fine matrix (Porphyry)– Phaneritic: Medium to Large interlocking crystals
(Granite, Diorite, Gabbro)
TexturesGlassy
Aphanitic
Phaneritic
Porphyritic
Vesicles
• Vesicles are holes found ONLY in Igneous rocks.
• Formed from trapped gasses when lava erupts• Examples: Scoria, Pumice, Basalt (sometimes)
Tectonic Plate Boundaries
• Places where tectonic plates converge, diverge, or slip past each other.
Igneous Rocks form at Convergent Boundaries
• Ocean-Continent Convergent Boundary.
• Forms volcanoes like those in Washington State.
Igneous Rocks form at Divergent Boundaries
• Divergent Boundary or Spreading Ridge
• Forms volcanoes like those that make up Iceland and the mid-Atlantic Ridge.
Mid-Atlantic Ridge
Igneous Rocks Form at Hot Spots
• A hot spot is where magma rises to the surface in the middle of a plate and not a plate boundary.
• Forms volcanoes like those in Hawaii or Yellowstone.
Hot Spots
Hawaii Yellowstone