Types of Rocks

Ms. Sikes

Igneous Rocks

• Form from magma

• 2 types:– Intrusive: (inside) rock formed

from magma beneath the earth’s surface–Extrusive: (outside) rock

formed as a result of volcanic activity at or near earth’s surface

Igneous Rocks cont…

• Texture is determined by how fast it cools. – Slow = coarse (bumpy) texture– Fast = fine (smooth) texture

Examples of Igneous RocksPUMICE

OBSIDIAN

GRANITE: the most abundant igneous rock

Sedimentary Rocks

• Formed when sediment (gravel, sand, mud, silt) forms layers and are compacted (smushed) together

• Forms at the earth’s surface (often in the bottom of lakes and oceans)

Sedimentary Rocks cont…• 3 types of Sedimentary Rocks:– 1. Clastic- made of rock fragments and

cemented together by a mineral like calcite or quartz (these look grainy) (sandstone)

– 2. Chemical- form from dissolved minerals in water (halite)

– 3. Organic- form from fossils of animals (coal)

Characteristics of Sedimentary Rocks

• Usually in layers (strata)

Examples of Sedimentary Rocks

• See page 373 in book

Metamorphic

• What does the word metamorphosis mean? Where have you heard it before?

Metamorphic Rocks

• Were originally sedimentary or igneous rocks

• Formed when: heat or pressure is different from what the rock is used to and it changes the rock

• Usually rocks change at temps between 50 degrees Celsius to 1000 degrees Celsius

Ways that rocks can metamorphasize

• 1. rock is heated by nearby magma

• 2. pressure builds up in rocks which causes it to change

Texture of Metamorphic Rocks

• Foliated: mineral grains are arranged in bands

• Nonfoliated: mineral grains are randomly arranged

Slate Marble

Picture tour of book

• Look on pages 369-380

Classify your rocks

• Which ones are sedimentary?

• Which ones are Igneous?

• Which ones are metamorphic?

• Can you name any of them?

Exit Ticket

• On a post it note:• Explain how each type of rock is

formed:• 1. metamorphic• 2. sedimentary• 3. igneous