Aim: How are Igneous Rocks formed?

Do Now: Take out your ESRT and turn to page 6. Look at the chart called Scheme for Igneous Rock identification and answer the questions below.

1) What types textures of igneous rocks will we see?

2) List the two environments of formation for Igneous Rocks?

- what do you think “in” and “ex” refers to in each word?

I. Igneous Rock:

•Igneous means “fire”

•These rocks come from very hot material such as magma or lava.

- Magma is found below the crust (inside the Earth)

- Lava is found on top of the crust (Outside the Earth)

II. Environment of Formation

A. Intrusive (plutonic) – when magma cools/hardens beneath Earth’s surface. (intrusive = inside)

Granite

•Magma cools slowly underground.

•Creates a coarse texture. (large crystals)

B. Extrusive (volcanic) - when lava cools/hardens above the Earth’s surface.

• Lava cools quickly on the surface.

•Creates fine, glassy and vesicular textures.

Rhyolite

III. Textures

- Coarse (large) crystals

- Fine (small) crystals

- Glassy (no crystals)

- Vesicular (gas pockets)

Pumice

ObsidianRhyolite

Granite

With your partner, take 3 min to walk around the room and find the 4 cards labeled Rock A,

B, C and D.

Identify the Texture of each group of rocks at the card using your notes we just took.

IV. Other Characteristics

• Color is described as light or dark

• Density is described as high or low

• Composition is described as:

- Mafic: containing Iron (Fe) and Magnesium (Mg)

- Felsic: containing Silicon (Si) and Aluminum (Al)