03 igneous rx_students_revised

CH. 3 – IGNEOUS ROCKS

Ignis =

Igneous Rocks

Cooling & crystallization of magma

Lava = molten rock at surface

Igneous Rocks

Classified by:

Texture = crystal size of minerals

Composition = minerals present

Texture of Igneous Rocks

Depends on magma’s cooling rate

1) Cools slowly (stays liquid longer)

- crystals are (large, small)

2) Cools quickly

- crystals are (large, small)

Texture (Crystal Size)

Two environments where magma cools:

1) Deep underground

2) At surface

Types of Texture

1) Fine-grained

- crystals invisible to naked eye

- magma cooled _________

- extrusive/volcanic

Types of Texture

2) Vesicular

- fine-grained w/ many holes in it

Types of Texture

3) Coarse-grained

- crystals easily visible

- magma cooled __________

- intrusive/plutonic

Types of Texture

4) Porphyritic

- two size crystals in same rock

Large crystals = ___________

Small crystals = ___________

Porphyritic Texture

2-stage cooling process:

1st stage = slow cooling at depth

__________ is formed

2nd stage = rapid cooling of remaining magma

____________ is formed

Types of Texture

5) Glassy

- no crystalline structure (magma cools too fast)

Igneous Rock Classification

Composition = ______________

Mostly silica with varying amounts of other six elements (Fig 2.21)

Importance of Igneous Rocks

Compose 90% of Earth’s crust

Two types of crust:

Continental crust = ________

Oceanic crust = ________

Bowen’s Reaction Series

Sequence of minerals crystallizing from magma (Fig. 3.13)

First minerals to form = _______

Last minerals to form = _______

Bowen’s Reaction Series

As rock is heated:

First minerals to melt = ________

Last minerals to melt = ________

Important Concepts

A mineral is stable if the environmental conditions are similar to where it formed

Ex: temperature, pressure, water- content

Important Concepts

If a mineral is put under different environmental conditions, it becomes unstable

- mineral reacts to new environment by changing

New Environmental Conditions:

If at the surface, weathering occurs

If within the crust, metamorphism occurs