1. Chapter 5 – Igneous Rocks

2. What are Igneous Rocks?
Igneous rocks are formed from the crystallization of magma
Lava is the rock that flows out of the Earth’s surface

3. Types of Igneous Rocks
Fine-grained rocks that cool quickly on Earth’s surface are called extrusive rocks
Coarse-grained igneous rocks that cool slowly beneath Earth’s surface are called intrusive rocks
Granite is the most common intrusive igneous rocks

4. Composition of Magma
Magma is often a slushy mix of molten rock, gases, and mineral crystals
The elements found in magma are the major elements found in Earth’s crust: oxygen, silicon, iron, aluminum, magnesium, calcium, potassium, and sodium
Silica (SiO2) is the most abundant and has the greatest effect on magma characteristics
There are 3 types of magma – basaltic, rhyolitic, andesitic

5. Origins of Magma
In lab, most rocks must be heated to temps around degrees Celsius before they melt
In nature these temps are found in the upper mantle and lower crust

6. Partial Melting
Not all minerals have the same melting points – because of this not all parts of the rock melt at the same time
This explains why magma is often a slushy mix of crystals and molten rock
Partial melting is when some minerals melt at low temps and other minerals remain solid