Earth_materials_2 - Rock types are distinguished by their...

Rock types are distinguished by their origin
Yosemite Valley, CA
• Igneous
• Sedimentary
• Metamorphic

1. Igneous rocks – formed by solidification (cooling) of magma
intrusive igneous rocks
extrusive igneous rocks

Lava flows in Hawaii
This lava solidifies to form basalt

Properties of rocks important for environmental geology:
• Strength
•
Texture – the arrangement and size of mineral grains
•
Porosity – amount of open pore space
•
Permeability – ability of fluid to move through material
•
Structure

Textures in igneous rocks
Interlocking texture – common in many igneous rocks; also occurs in
some metamorphic rocks and some sedimentary rocks. Note that there
is almost no open pore space with this texture.

Interlocking texture
in igneous rock
Coarse grain size in
intrusive igneous rocks
Granite
counter-top

Volcanic rocks have fine grain size
because of rapid solidification
Some volcanic rocks have
vesicular texture (this
reduces strength)
Extremely rapid cooling results in glass
Obsidian

2. Sedimentary rocks