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

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/ Weathering

Erosion/ W

eathering

Heat and Pressure

CoolingHeat

Heat

Pressure E

rosi

on

Define - Freeze

?

?

Igneous Rocks

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 SeriesThe 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 Melting2. 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 Melting3. 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 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 content

75% SiO2 - "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

Textures of Igneous Rocks

Phaneritic (course grained)

Aphanitic (fine grained)1.

2. Magma

LavaEarth’s surface

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 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 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