Chapter 5 and 6. Section 5.1 Igneous rocks are formed from the crystallization of magma Igneous comes from Latin ignis which means fire Lava is magma.

RocksChapter 5 and 6

What are Igneous Rocks?

Section 5.1

Types of Igneous Rocks• Igneous rocks

are formed from the crystallization of magma• Igneous comes

from Latin ignis which means fire

• Lava is magma that flow out onto earth's surface

Types of Igneous Rocks Cont…

• Extrusive igneous rocks are fine-grained igneous rocks that cool quickly on earth’s surface • Pumice or obsididan

• Intrusive igneous rocks are coarse grained igneous rocks that cool slowly beneath the earth’s surface• Granite is the most common

• Studies of granite formations reveal they cut across other formations, evidence of intrusion

Composition of Magma Magma is a slushy mix of molten

rock, gases and mineral crystals Silica (SiO2) is the most abundant

mineral in magma and has the greatest effect on magma characteristics

Magma Formation Temperature,

pressure, water content and mineral composition affect magma formation

Temperature and pressure increase with depth in the Earth’s crust

Pressure increases a rocks melting pointo 1100 vs 1400

Magma Formation cont…

Rocks and minerals contain small percentages of water which decreases a rocks melting point

Minerals have different melting points

Rocks only melt at certain conditions MUST have the right temperature,

pressure, and mineral composition

How Rocks Melt Rocks are made of different minerals Minerals have different melting

points so parts of a rock will melt at different times

Partial melting is a process where some minerals melt at low temperatures while others stay solid

Fractional Crystallization

Just as minerals melt at different rates, they cool at different rates as well

Fractional crystallization is a process where minerals forma at different temperatures

The last minerals to melt are the first minerals to crystallize

CLASSIFYING IGNEOUS ROCKS

Section 5.2

Mineral Composition Three main groups of igneous rocks

o Felsic, mafic, intermediate Felsic rocks such as granite are:

light colored, high silica contents, contain quartz and feldspars

Mafic rocks such as gabbro are dark colored, and rich in iron and magnesium

Grain Size Igneous rocks differ in the size of

their grains Grain size is determined by the

cooling rate When lava cools quickly, small grains

form When lava cools slowly, large grains

form

Igneous Rocks as Resources

Very useful for building materials because their interlocking grains make them strong

Also resistant to weathering Granite is commonly used for

building

Ore Deposits Ores are minerals that contain a

useful substance that can be mined at profit

Valuable ore deposits are often associated with igneous intrusions

Ore Deposits: Veins Mineral rich magma fills the cracks

and voids of surrounding rock During magma crystallization, water,

silica and any metals not common in minerals (gold, silver, lead, copper) are left over and eventually solidify to form veins

Ore Deposits: Pegmatites

Vein deposits main contain other valuable resources in addition to metals

Veins of extremely large grained minerals are called pegmatites

Rare elements and crystals are found in pegmatites

Ore Deposits: Kimberlites

Rare, ultramafic rocks that can contain diamonds or other minerals formed only under very high pressures

Formation of Sedimentary

RocksSection 6.1

Formation of Sedimentary Rocks

Sediments are pieces of solid material that have been deposited on Earth’s surface by wind, water, ice, gravity or chemical precipitation

When sediments become cemented together, they form sedimentary rocks

Weathering Weathering is a set of physical and

chemical processes that break rock down

Chemical weathering occurs when rocks are dissolved or chemically changed

Physical weathering occurs when rocks break off but remain chemically unchanged

Erosion and Transport Erosion is the removal and

movement of surface materials from location to another

4 main agents: Wind, moving water, glaciers and gravity

Deposition Deposition occurs when sediments

are laid down on the ground or sink to the bottom of water

Sediments in water will create layers, with large particles settling first

Wind only moves fine sediments Glaciers and landslides move all

sediments equally

Burial Most sediments are deposited in

basins where the building layers increase pressure and temperature

Increasing pressure and temperature cause lithification, or the chemical and physical processes that transform sediments into sedimentary rocks

Lithification Lithification begins with compaction The weight of overlying sediments force

sediments together The temperature in earth's crust are high

enough to cause cementation Cementation occurs when mineral growth

cements sediments together into solid rock

Lithification cont… Two types of

cementation New minerals can

grow between sediment grains

The same mineral grows between the sediment grains

Features of Sedimentary Rocks

The primary feature of sedimentary rocks is horizontal layering called bedding

Bedding with particle sizes that become heavier at the bottom is called graded bedding

Cross-bedding is another type of bedding where layers of inclined sediment move forward across a horizontal surface

Metamorphic RocksSection 6.3

Causes of Metamorphism

Meta means change and morphe means forms

During metamorphism, rocks change form while remaining solid

Pressure and temperature increase with depth

Temperature comes from earths internal heat

Pressure comes from overlying rocks or compression during mountain building

Types of Metamorphism

When high temperature and pressure affect large regions of crust, they produce large belts of regional metamorphism

When molten rock come into contact with solid rock, a local effect called contact metamorphism occurs

When very hot water reacts with rocks and alters its chemistry and mineralogy, hydrothermal metamorphism occurso Occurs near igneous intrusions and active

volcanoes

Metamorphic Textures Metamorphic rocks have two textural

groups: foliated and nonfoliated Wavy layers and bands of minerals of flat

crystals characterize foliated metamorphic rockso Schist from shale (clay) and gneiss from

granite

If I said you were gneiss, I’d be for of schist! lol

Metamorphic Textures Cont…

Nonfoliated rocks lack mineral grains with flat crystals and instead have blocky crystal shapeso Quartzite from quartz-rich sandstone and

marble from limestone

The Rock Cycle The continuous changing and remaking of rocks is

called the rock cycle Igneous rocks crystalize from magma Sediments cement together to form sedimentary Pressure and temperature form metamorphic rock All rocks can change into one another!