Rocks• Naturally occurring • Solid substance • Made of minerals

3 types of rocks• Sedimentary• Igneous• Metamorphic

Rocks can be compared to cookies

Sedimentary rocks• Formed from sediment (small particles of

rock) pressed and cemented together over millions of years.

• Limestone made from particles of calcite (fizzed with acid)

• Sandstone: made from sand size particles; rough• Shale: made from very small particles, smooth and

black.

Sedimentary rock forms layers

Remember the Grand Canyon activity? Which layer is the oldest?

Igneous Rocks• Formed when molten rock cools and hardens

– Magma is molten rock below the surface– Lava is molten rock above the surface

Extrusive igneous rocks• Form above the surface

• Lava cools quickly • Small grains

Intrusive igneous rocks• Form below the surface• Magma cools slowly

• Large grains

Granite

• Igneous rock with large grains/crystals• Formed when magma cools and hardens• Is it intrusive or extrusive?

Basalt

• Formed when flowing lava cools and hardens • Small grains• Is it intrusive or extrusive?

Pumice

• Formed when bubbling lava cools and hardens• Small grains with air holes from bubbles;

igneous rocks with air holes are called vesiculated.

• Intrusive or extrusive?

Obsidian (Volcanic glass)

• Formed when lava cools and hardens very quickly

• Very tiny grains or no grains at all• Intrusive or extrusive?

Metamorphic Rock

• Formed when extreme heat and pressure below the surface of the earth change existing rocks into another rock.

PARENT ROCK METAMORPHIC ROCK

What changes?• The minerals may change to another mineral by

chemical reactions.• The arrangement of minerals may change; they

might line up and form bands; this is called foliation.

Marble

• A metamorphic rock that comes from limestone

• The calcite has formed larger crystals• Marble reacts to acid..

Gneiss (“nice”)

• Formed from granite or shale• The minerals become arranged in bands.

Quartzite

• Forms from sandstone• The minerals from the sand (quartz) grow

together to form bigger crystals.

Slate

• Formed from shale that is compressed over a long period of time.

Rock Cycle