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Rock types and the rock cycle
Rock types and the rock cycle
Rock types and the rock cycle
Rock types and the rock cycle
Characteristics of magma
• Parent material of igneous rocks is magma
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Characteristics of magma
• Parent material of igneous rocks is magma
• Forms from partial melting of rocks inside the Earth
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Characteristics of magma
• Parent material of igneous rocks is magma
• Forms from partial melting of rocks inside the Earth
• Magma that reaches the surface is called lava
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Magma to lava
How are magmas produced?
How are magmas produced?
How are magmas produced?
How are magmas produced?
How are magmas produced?
How are magmas produced?
How are magmas produced?
How are magmas produced?
The nature of magma
Consists of three components:
Melt _ liquid _ mobile ions
Solids - silicate minerals (mostly)
Volatiles - dissolved gases H2O, (CO2), (SO2)
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How does a rock crystallize from a melt?
Si-O tetrahedra form first
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How does a rock crystallize from a melt?
Si-O tetrahedra form first
Tetrahedra connect with each other and other ions
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How does a rock crystallize from a melt?
Si-O tetrahedra form first
Tetrahedra connect with each other and other ions
Minerals form in a specific order
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How are igneous rocks classified?
1)Texture
2) Chemistry
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Extrusive versus intrusive rocks
Rocks formed from lava at the surface are extrusive, or volcanic rocks
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Extrusive versus intrusive rocks
Rocks formed from lava at the surface are extrusive, or volcanic rocks
Rocks formed from magma that crystallizes at depth are intrusive, or
plutonic rocks
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Question:
If intrusive rocks form at depth, how do we know about
them?
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Answer:
Intrusive igneous rocks are uplifted by tectonic forces
and stripped of the overburden by erosion
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Outcrops of intrusive igneous rocks
Rate of Cooling
Rate of Cooling
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Slow rate promotes growth of fewer but larger crystals
Fast rate promotes growth of many, small crystals
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Types of igneous textures
Phaneritic
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– coarse-grained = coarsely crystalline
– Crystals can be identified without a microscope
– Slowly crystallized
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Types of igneous textures
Aphanitic
fine-grained = finely crystalline
– Microscopic crystals
– Crystals formed in a short time
– May contain vesicles (holes from gas bubbles)
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Texture = coarsely crystalline (phaneritic)
Phaneritic texture
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Aphanitic texture
Vesicular basalt
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Texture in a lava that cools extremely quickly?
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Glassy texture (obsidian)
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Types of igneous textures
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Glassy texture
– Very rapid cooling
– obsidian
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Pumice (frothy glass)
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Types of igneous textures
Porphyritic
Large crystals – phenocrysts - embedded in a matrix of smaller crystals
- the groundmass
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Porphyritic andesite (andesite porphyry)
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Porphyritic andesite
Porphyritic texture
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Types of igneous textures
Pyroclastic
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– Various fragments ejected during a violent volcanic eruption
– Textures often appear more similar to sedimentary rocks
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Types of igneous textures
Pegmatitic
Exceptionally coarse grained (coarsely crystalline)
Form in late stages of crystallization of granitic magmas
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How are igneous rocks classified?
1) Texture
2) Amount of silica (SiO2) in the whole rock
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Rhyolite (granitic/felsic composition)
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Diorite (andesitic/intermediate)
Gabbro (mafic/basaltic)
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Relationships among magma types / appearances and volcanic eruption / landform
types
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