1. What are rocks?

2. Types of rocks
The 3 types are:
Igneous
Sedimentary
Metamorphic

4. Igneous rocks
Igneous rocks are formed from molten rock called magma. They are mostly crystalline (made up of interlocking crystals) and usually very hard to break. E.g. granite, basalt, andesite.
Basalt
Granite

5. The formation of igneous rocks
Extrusive
igneous rocks are
cooled quickly
so small crystals form (e.g. basalt).
volcano
Sedimentary
rocks
Intrusive
igneous rocks are cooled more slowly so large crystals form (e.g. granite).
magma

6. Basalt pillars
These pillars were formed when lava cooled on the Earth’s surface.

7. Sedimentary
Sedimentary rocks are formed from sediment grains deposited by water, wind or ice. They are always formed in layers, called “beds” or “strata”, and quite often contain fossils. E.g…
Sandstone
Limestone
Chalk

8. The formation of sedimentary rocks
These were formed from layers of sediment which were squeezed together.
new
deposits
rivers
sea/lake/river
land
layers of
sediments
getting
older

9. Metamorphic
Metamorphic rocks were once igneous or sedimentary rocks, but have been changed (metamorphosed) as a result of intense heat and/or pressure within the Earth’s crust. E.g…
Marble
Gneiss, pronounced ‘nice’
Slate

10. Metamorphic rock - formation
Metamorphic rocks are formed by the effect of extreme pressures and temperatures deep within the Earth.
This alters the structure of the existing rock.

11. The formation of metamorphic rocks
sedimentary
rocks
are changed
here due to
heat and pressure.
volcano
Sedimentary
rocks
magma

12. Metamorphic rocks
Continent collision causes metamorphism and huge folds like this one in Scotland.

13. Rock type
Definition
Formation
Example
Igneous
Rocks formed of interlocking crystals. Tough, hard and resistant to erosion
Formed by the cooling of molten magma either underground (intrusive) or on the ground (extrusive) due to volcanoes
Basalt, granite
Sedimentary
Formed in layers called strata. Often contain fossils. Some are tough and others are weaker than igneous or metamorphic rocks
Formed by the compaction of sediments, usually deposited by the sea.
Sandstone, limestone, shale, clay
Metamorphic
Also formed of interlocking crystals. Very tough and resistant to erosion
Formed by heat and/or pressure changing existing sedimentary or igneous rocks to metamorphic rocks
Slate, marble

14. Metamorphic rocks slate and marble
rocks are broken
up by the action
of weather
rocks rise
to surface by
uplift and erosion
volcano
transportation
and deposition
sea
rises to surface
where it
cools rapidly
high pressure
and temperature
slow
solidification
melt
magma
Igneous rocks
granites
magma
Igneous rocks
basalt
Sedimentary rocks
mudstone
Metamorphic rocks slate and marble

15. Metamorphic rocks slate and marble
rocks are broken
up by the action
of weather
volcano
rocks rise
to surface by
uplift and erosion
transportation
and deposition
Igneous rocks
basalt
sea
Igneous rocks
granites
Sedimentary rocks
mudstone
rises to surface
where it
cools rapidly
high pressure
and temperature
slow
solidification
Metamorphic rocks slate and marble
melt
magma

16. Homework:
Rock On!
Task – imagine you are a rock, describe your journey through the rock cycle.
Things to include:
Are you an igneous, metamorphic or sedimentary rock?
What type of rock are you e.g. granite, limestone.