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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 Sedimentary Rocks Igneous Rocks Metamorphic Rocks Magma Sediment Pressure And Cementation Erosion/ Weathering Heat and Pressure Cooling Heat Pressure Erosion

Define - Freeze ? ?

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 [800 o C and 1200 o C] Source of heat [radioactive decay]

Geothermal Gradient – the rate at which temperature increases with depth in the Earth 30 O C/km

Bowen’s Reaction Series The order of crystallization of the common silicate minerals from a magma Liquid Solid

Iron and Magnesium rich Al, Ca, and Sodium rich Dark colored minerals Light colored minerals

Factors controlling Melting 2. Pressure: as pressure increases, melting temperature increases as pressure decreases, melting temperature decreases Lowering pressure causes melting in divergent margins.

Relationship between P, T, and Melt Less Pressure More Pressure

Divergent Plate Boundary

Factors controlling Melting 3. Water content: As water content increases, melting temperature decreases

Caramel is melted sugar

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 flow honey – high viscosity water – low viscosity Viscosity increases as silica content increases.

Magma Chemistry Molten material can consist of liquid rock, mineral grains and gases (H 2 O, CO 2, SO 2 ). Silicon and oxygen (SiO 2 ) make up the majority of magma 45% SiO 2 - "low" silica content 75% SiO 2 - "high" silica content

Endmember Magma Chemistry Mafic – low SiO2 / high iron, magnesium Felsic/Silicic – high SiO2 / high 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

Phaneritic (course grained) Aphanitic (fine grained) Magma Lava Earth’s surface

Aphanitic Texture – Rapid Cooling Small Crystals

Phaneritic Texture – Slow Cooling Large Crystals

Phaneritic Texture – Slow Cooling Large Crystals Aphanitic Texture – Rapid Cooling Small Crystals Silicic Chemical Composition GraniteRhyolite

Phaneritic Texture – Slow Cooling Large Crystals Aphanitic Texture – Rapid Cooling Small Crystals Intermediate Chemical Composition DioriteAndesite

Phaneritic Texture – Slow Cooling Large Crystals Aphanitic Texture – Rapid Cooling Small Crystals Mafic Chemical Composition GabbroBasalt

PHANERITIC texture It means that the size of all grains in the rock are large enough to be distinguished with the unaided eye

APHANITIC texture It means that not all grains in the rock are large enough to be distinguished with the unaided eye. Most of the rock is background mass.

Pegmatites

Ingersoll Mine Ingersoll mine, Pennington Co., South Dakota, United States One of the many adits at the old Ingersoll pegmatite. Private and Very dangerous. No Trespass.

Glassy Texture - Very Rapid Cooling - No Crystal Structure

Ash FallAsh Flow Pyroclastic Texture

Plutonic Structures