SOL 6 A.Igneous (Intrusive and Extrusive) Rocks;

Unit 4 Day 4

Igneous Rocks

SOL 6 a.igneous (intrusive and extrusive) rocks;

Objective

Classify igneous rocks by mineral content and texture. 1. 1. – granite;

2. – pumice, obsidian, and basalt.

Endurung Understanding

The rock cycle is an ongoing process by which rocks are formed. It gives us an explanation of how Earth materials are through time.

Igneous Rocks

Minerals combine in the Earth’s crust to form rocks. Most rocks are made of one or more minerals. Igneous rocks were the first type to form on Earth as its molten surface

and

Igneous Rocks form from the crystallization of

 is molten rock below Earth’s surface

 is magma that flows out onto Earth’s surface

Igneous Rock Types

Igneous rocks are classified based upon where they

Extrusive igneous rocks on the surface and are (small crystals)

Other common extrusive igneous rocks include ,

, and

igneous rocks beneath the surface and are coarse-grained (larger crystals)

Magma

Magma is often a slushy mix of molten , and mineral crystals

Silica (SiO2) is the most common compound in magma and has the greatest effect on its characteristics

Magma Formation

There are four main factors that affect magma formation

 . Heat comes from the remaining energy from Earth’s formation and the decay of radioactive elements

 . The pressure increases with depth

 . More decreases the melting point of the rocks

 . Minerals melt at different temperatures

Classifying Igneous Rocks

Extrusive and intrusive igneous rocks are further classified by their

Classifying Igneous Rocks

Felsic rocks are light colored, have high silica contents, and contain quartz and the feldspars orthoclase and plagioclase

 is the most common felsic rock

Classifying Igneous Rocks

.rocks are dark, have lower silica contents and are rich in iron and magnesium

 is a mafic rock

Classifying Igneous Rocks

Bowen’s Reaction Series

As magma, minerals form in predictable patterns. The reaction series has two main branches of crystallization

Feldspars undergo a continuous change in composition. The first to form are rich in calcium and as cooling continues the feldspars react with the magma and change to sodium rich

 Iron-rich minerals undergo abrupt changes during fractional crystallization

As minerals form in the order shown in Bowens reaction series elements are removed from the remaining magma. . are the most abundant elements and are left over at the end of the reaction series. The finally crystallizes to form .

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