ROCK TYPES
IGNEOUS ROCKS
 Rocks which were at one time molten
 Igneous means “__________ ___________” i.e. volcanic rocks
 2 important categories:
-volcanic (________________)
-plutonic (________________)
Plutonic / Intrusive
 Formed when magma is cooled deep within the earth’s surface.
 Crystals in plutonic rock are ___________, since the rock has cooled
_____________ and crystals have had a ___________ time to form.
 e.g. granite (contains obvious crystals)
Volcanic / Extrusive
 Formed when lava is cooled quickly on the earth’s surface.
 Crystals in volcanic rock are ___________ since the crystals have
___________ time to form before the rock soildifies.
 e.g. basalt, scoria, tuff, pumice (all have airholes = light!)
SEDIMENTARY ROCKS
 Rocks which have been formed from ________________ (gravel and sand)
from the earth’s surface. These sediments have been compressed,
cemented together and hardened (process = ____________________).
 Streams carry lots of sediments (weathered materials). These are
deposited on the bottom of rivers, lakes etc – the largest sediments are
deposited _____________ and the smallest _____________.
 Sediments are laid down in layers and compressed by tonnes of material
on top of them
 Characteristics:
- Soft rocks
- _____________ evident
- ___________ grained
- Fossil imprints
 eg: limestone, sandstone, mudstone
METAMORPHIC ROCK
 Rocks that have been altered by the effects of _____________ and
___________________. Both igneous and sedimentary rocks can change
into metamorphic rocks.
 Characteristics:
- Extremely hard
- Often have ____________ crystals
- Sometimes crystals arranged in ______________
 eg. marble (parent rock – limestone), quartzite (parent rock – sandstone)