Purchase lab manual in lab this week Homework 1 due in lab this week
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Transcript of Purchase lab manual in lab this week Homework 1 due in lab this week
Purchase lab manual in lab this week
Homework 1 due in lab this week
Homework 2 due in lab next week
Read Mt. Saint Helens disaster paper
Igneous Rocks
Mineral -Naturally formed-Solid-Formed by inorganic processes-Specific chemical composition-Characteristic crystal structure
Earth Materials continued
Rock – a coherent, naturally occurring solid, consisting of an aggregate of one or
more minerals, or a mass of natural glass or organic matter.
Basic Rock Classifications
•Igneous
•Sedimentary
•Metamorphic
Rock Cycle
SedimentaryRocks
IgneousRocks
MetamorphicRocks
Magma
Sediment
Pressure
And Cementation
Erosion
Erosion
Heat and Pressure
CoolingHeat
Heat
Pressure Ero
sion
Define - Freeze
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Igneous Rocks -a rock that forms when hot molten rock
(magma or lava) cools and freezes solid
Two types of igneous rocks• Plutonic – cools underground• Volcanic – cools above ground
Factors controlling Melting
1. Temperature:
Melt at [800oC and 1200oC]
Source of heat [radioactive decay]
Geothermal Gradient – the rate at which temperature increases with depth in the Earth
30OC/km
Bowen’s Reaction Series
Factors controlling Melting2. Pressure:• as pressure increases, melting
temperature increases• as pressure decreases, melting
temperature decreases
Lowering pressure causes melting in divergent margins.
Divergent Plate Boundary
Relationship between P, T, and Melt
Factors controlling Melting
3. Water content:as water content increases, melting temperature decreases
Water in rocks causes melting in convergent margins.
Water increases melting at convergent plate boundaries
Where do igneous rocks occur?
Types of Molten Material
1. Magma – molten material below the Earth's surface
2. Lava – molten material above the Earth's surface
Magma Composition Changes
•Partial melting•Assimilation•Magma Mixing•Fractional Crystallization
Partial Melting
some minerals melt at a lower temperature than others.
Magma Viscosity
Viscosity – resistance to flowhoney – high viscositywater – low viscosity
Viscosity increases as silica content increases.
Magma Chemistry
Molten material can consist of liquid rock, mineral grains and gases (H2O, CO2, SO2).
Silicon and oxygen (SiO2) make up the majority of magma
45% SiO2 - "low" silica content75% SiO2 - "high" silica content
Endmember Magma Chemistry
Mafic – low SiO2, iron, magnesium
Felsic/Silicic – high SiO2, aluminum, calcium, sodium
Igneous Rock Types
Intrusive (plutonic) rock – cools and solidifies below the Earth's surface.
Extrusive (volcanic) rock – cools and solidifies above the Earth's surface.
Texture – overall appearance, related to size, shape, and arrangement of minerals.
Texture is related to cooling history of an igneous rock, not its chemistry.
Textures of Igneous Rocks
Textures of Igneous Rocks
Phaneritic (course grained)
Aphanitic (fine grained)
1.
2.
3.
4.
Glassy
Vesicular
Magma
Lava
Felsic/ Silicic Mafic
light colored intermediate dark colored
high in SiO2 low in SiO2
Phaneritic Plutonic (magma)
(coarse grained) Intrusive
Aphanitic Volcanic (lava)
(fine grained) Extrusive
Igneous Rock Classification
Granite
Rhyolite
Diorite Gabbro
Andesite Basalt
Increasing Fe and Mg
Increasing silica content
Aphanitic Texture – Rapid Cooling Small Crystals
Phaneritic Texture – Slow Cooling Large Crystals
Phaneritic Texture –Slow Cooling
Large Crystals
Aphanitic Texture –Rapid CoolingSmall Crystals
Silicic Chemical Composition
Granite Rhyolite
Phaneritic Texture –Slow Cooling
Large Crystals
Aphanitic Texture –Rapid CoolingSmall Crystals
Intermediate Chemical Composition
Diorite Andesite
Phaneritic Texture –Slow Cooling
Large Crystals
Aphanitic Texture –Rapid CoolingSmall Crystals
Mafic Chemical Composition
Gabbro Basalt
Phaneritic
Porphyritic-Phaneritic
Phenocrysts in Groundmass
Aphanitic
Porphyritic-Aphanitic
Phenocrysts in Groundmass
Pegmatites
Ingersoll Mine Ingersoll mine, Pennington Co., South Dakota, United StatesOne of the many adits at the old Ingersoll pegmatite. Private and Very dangerous. No Trespass.
Glassy Texture - Very Rapid Cooling - No Crystal Structure
Ash Fall Ash Flow
Pyroclastic Texture
Plutonic Structures
Plutonic Structures