1. Igneous Rocks
Chapter 5

2. Vocabulary
Radioactivity-the spontaneous process through which unstable nuclei emit radiation.
Lava-magma that flows out onto Earth’s surface.
Igneous rock- rocks formed from the crystallization of magma.

3. Vocabulary
Partial melting- the process by which some minerals melt at low temperatures while other remain solids.
Fraction crystallization- the process by which different minerals from at different temperatures.
Bowen’s Reaction Series- a model that describes the relationship between cooling magma and mineral formation.

4. Composition and Origins of Magma
I. Composition of magma
Magma is a mixture of molten rock, gases, and mineral crystals.
The elements in magma are the eight major elements in Earth’s crust.
1. The most abundant compound in magma
is Silica (SiO2).
C. Magmas are classifies as basaltic, andesitic, and
rhyolitic.
1. Their classification depends on how much
silica they contain.

5. Composition and Origins of Magma
Temperature
Pressure
Increase with depth
In Earth’s crust.
Increases with depth under the surface
Factors in the
formation of
magma
This is known as the geothermal gradient.
Which increases the melting point of rock
Water content
Mineral content
As this increases, the melting point decreases.
Different minerals have different melting points.

6. How Rocks Melt
When a rock begins to melt, the minerals with the lowest melting point melt first. The elements in these minerals from the liquid part of magma. As other minerals melt, the elements in those minerals are added to the magma and change its composition. The opposite happens as the magma cools. The elements in the minerals are removed from the magma in the order that the minerals crystallize, which is fractional crystallization.

7. Bowen’s Reaction Series

8. Partial Melting
Partial melting is when different minerals within a rock melt at different rates. When different minerals are melted new elements are added to the magma mixture changing the chemical composition.

9. Synthesize
Both branches show that minerals from in predictable patterns in cooling magma. However, in the right branch, the feldspar minerals undergo continuous change. The iron-magnesium minerals, in the left branch, undergo abrupt changes.

10. Section 5.2 Vocabulary
Magma- molten material found under Earth’s surface.
Intrusive Rock- Igneous Rock that cool slowly beneath Earth’s surface.
Extrusive Rock- Igneous rock that cool quickly on Earth’s surface.
Granitic Rock- Light-colored rock high in silica and contains quartz and feldspar.
Basaltic Rock- Dark-colored rock low in silica and contains iron and magnesium-rich materials.

11. Section 5.2 Vocabulary Cont.
Texture- the size, shape, and distribution of crystals or grains that make up a rock.
Porphyritic texture- characterized by large, well-formed crystals surrounded by finer-grained crystals of the same mineral or different minerals.
Vesicular Texture- A spongy appearance caused by broken gas bubbles
Pegmatite- veins of extremely large grained minerals.
Kimberlite- a rare, ultramafic variety of peridotite that forms pipe like structures and which sometimes contain diamonds.

12. Types of Igneous Rock Intrusive -Coarse-grained -Cool slowly
-Form beneath surface
Ex. granite
Extrusive
- Fine-grained
- Cool quickly
- Form above surface
- Ex. Rhyolite
Igneous Rocks
Formed by crystallization of magma

13. Mineral Composition
basalt: ___________________________
_______________________________
2. obsidian: ______________________________
3. peridotite: _________________________
__________________________
4. diorite: ____________________________
____________________________
5. pegmatite: _________________________
A fine-grained rock containing
plagioclase, feldspar, biotite, pyroxene, amphibole, and olivine
A felsic extrusive, noncrystalline rock
A rock that contians only
pyroxene and olivine
A coarse-grained rock that is mostly
white, gray, and black
a very coarse-grained rock that
contains potassium feldspar

14. Grain Size
Describe the conditions that cause igneous rocks to form large grains or no visible grains.
Intrusive igneous rocks are formed when magma cools slowly beneath Earth’s surface, so large crystals have time to form. Extrusive igneous rocks cool quickly because they are exposed to air and moisture on Earth’s surface, so visible crystals do not have time to form.

15. Igneous Rocks as resources
List two characteristics of igneous rocks that make them good building materials.
1. They have interlocking grain textures, which give them strength.
2. They contain minerals that are resistant to wearing.

16. The fluid from which Magma crystallizes Contains high levels
Ore Deposits
The fluid from which
Magma crystallizes
Contains high levels
of ______________
________________.
Silica, water, and
Leftover elements
The fluid fills
___________
________.
Cracks, and
Voids in the
rock

17. The fluid solidifies to form
____________ containing
Metals such as _____,
_______, ____, _______, and
Rare elements such as
________ and __________.
Quartz veins
gold
silver
lead
copper
lithium
beryllium
Answer the synthesize question.

18. Other Information
Igneous is Latin for “from fire”