Week 4 Pt. 2 Flashcards
Magma
A body of molten rock found at depth, including any dissolved gasses or crystals
Lava
Magma that reaches the earths surface
Volatile
Gasses, gaseous components of magma dissolved in the melt. Volatiles will readily vaporize(form a gas) at surface pressures
Granitic (felsic) composition
A compositional group of igneous rocks indicating that the rock is composed of almost entirely light colored silicas
Basaltic (mafic) composition
A compositional group of igneous rock indicating that the rock contains substantial dark silicate materials and calcium rich plagioclase feldspar
Andesitic (intermediate) composition
A compositional group of igneous rocks that contains at least 25% dark silicate materials. The other dominant material is plagioclase feldspar
Ultra mafic
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Difference between lava and magma
Magma is molten rock below the surface of the earth, it is called lava when it reaches the surface and can come from volcanoes as lava
3 main components of magma
Liquid: melt
Solid: crystals of silicate materials
Gaseous: volatiles
Describe the crystallization process
As the temperature of the liquid drops, ions pack more closely together as their rate of movement slows. When they are cooled they confine to ions in an orderly crystalline arrangement. (Opposite of melting)
Compare and contrast extrusive and intrusive igneous rocks
Intrusive: magma, forms deep in earth, loses heat slowly, coarse grained(visible) crystals (phanaritic)
Extrusive: lava, on earths surface, loses heat fast, fine crystals(microscopic)
Igneous rocks are composed of mainly what mineral group
Silicate minerals
How do light colored igneous rocks differ from dark colored ones
Dark igneous rocks have dark minerals. They are mafic/ basaltic, more iron and mg more dense
Light= opposite, granitic
4 basic compositional groups of igneous rocks in order from highest Si content to least.
Granitic
Andesitic
Intermediate
Basaltic
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Define igneous texture
3 factors
- Rate at which molten rock cools( dominant)
- Amount of silica present in the magma
- amount of dissolved gasses in the magma
How does cooling rates influence crystal size
Bigger crystals can form when there is more time to cool.
6 major igneous textures
Glassy Porphyritic Phaneritic Vesicular Pyroclastic Aphanitic
How are granite and rhyolite different/ the same
Both fine grained/ might colored silicates.
Rhyolite is fine grained and contains glass fragments and voids from cooling rapidly at the surface, granite is intrusive.
Intrusive igneous rocks are also called _____
Plutonic
Extrusive igneous rocks are also called
Volcanic rocks
Glassy texture
Composed of unordered atoms
Porphyritic texture
2 distinctly different crystal sizes
Phaneritic
Mineral grains Large enough to see with a naked eye
Vesicular texture
Extrusive rock that contains holes from gas bubbles
Pyroclastic texture
Produced by the consolidation of fragments that may include ash, blobs, blocks from a volcanic explosion
Aphanitic
Fine grained, Crystals too small to see with a naked eye
How does magma rise
Density contrast
Overlying pressure
