c. Construct an explanation of how to classify rocks by ...€¦ · Rock Classification Rocks are divided into three main classes based on how they form: 1. Igneous 2. Sedimentary

S6E5. Obtain, evaluate, and communicate information to show how Earth’s surface is formed.

c. Construct an explanation of how to classify rocks by their formation

Objective: Students will complete the graphic organizer about formation of igneous rocks

Directions: Read each slide then complete the graphic organizer.

Rock ClassificationRocks are divided into three main classes

based on how they form:

1. Igneous

2. Sedimentary

3. Metamorphic

Each type of rock can be further classified based on:

Composition and texture

Composition

The chemical make up of the rock or what it is made of.

This can be minerals or other materials: shells, clay, plants, sand, pebbles

Texture/GrainsDetermined by the grains size, shape

and position.

Igneous can be fine or coarse grain

Sedimentary can be characterized by observing lithified (cemented) inorganic grains, minerals, organic material, or fossil fragments. The wide range of textures common in sedimentary rocks is separated into clastic, chemical, and bioclastic (biochemical) groups.

Texture/Grains

Metamorphic textures consist of two main types: foliated and non-foliated textures.

Texture can reveal the processthat formed the rock.

Igneous Rocks

What are they?

Rock made from cooled

–LAVA, above ground or

–MAGMA, below ground.

Classification

They are classified

in 3 ways:

1.Texture – Grain/ minerals

2.Origin - where formed

3.Mineral Composition –made from

Grain Size Have….

SPECIAL NAMES

Texture/GrainCoarse Grained = large grains, cooled slowly

Think about it…. If it cools over a long time – the grains have time to get big!

Most abundant intrusive rock is GRANITE

Fine Grained = small grains, cooled fastThink about it… If it cools over a short time – the grains don’t have time to get big!

Example: Basalt

Igneous Rock Formation-OriginExtrusive – formed ABOVE

GROUND. It cools fast so it has smallgrains.

Intrusive – formed UNDERGROUND. It cools slowly so it will have largegrains.

Laccolith

Examples of each type of ROCK Fine Grained

Basalt = Extrusive Igneous rock

Course Grained

Granite = Intrusive Igneous rock

Mineral Composition How much silica is in the magma/lava?

–Low silica content = dark colored = Mafic

–High silica content = light colored = Felsic

High Silica Content Low Silica Content

Felsic Igneous Rock Mafic Igneous Rock

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Lighter

Darker

Big Crystals Small or No CrystalsDraw pictures of the different types of Igneous Rocks!

Label the igneous rock formation

Ticket out: CHOOSE ONLY ONE

What makes up the grains in an igneous rock?

Illustrate grains of an igneous rock and explain why this happens

Compare and contrast intrusive and extrusive igneous rocks