Types of Rocks & the rock cycle.

2. What is a Rock?
• Naturally-occurring mixtures
of minerals, glass or organic
matter.

3. Types of Rocks?

4. What is the difference between
a rock and a mineral?
• Rocks are made up of ONE or
MORE minerals.

5. Once a rock is formed, does it
stay the same rock forever?
• NO!

6. • Rocks are continually changed by
many processes, such as
weathering, erosion, compaction,
cementation, melting, and cooling
• Rocks can change to and from the
three types

7. What is the process through
which rocks change?
• The Rock Cycle—earth materials
change back and forth among the
different types of rocks

9. • “Ignis” = Latin for “fire”
• Formed from the cooling of either
magma or lava
• The most abundant type of rock
• Classified according to their origin and
composition

10. ORIGIN— Where rocks are formed
• Below ground = from magma
• Usually have LARGE crystal grains
(they cooled slowly)

11. Some have large & small crystals

12. • Above ground = from lava
• Usually have SMALL or NO crystals
(they cooled too quickly)

13. Peridotite: How was it formed?
Give a reason for your answer.

14. Granite: How was it formed?
Give a reason for your answer.

15. Obsidian: How was it formed?
Give a reason for your answer.

16. Diorite: How was it formed?
Give a reason for your answer.

17. Basalt: How was it formed?
Give a reason for your answer.

19. • Formed from sediments
(rock fragments,
mineral grains, animal
& plant remains) that
are pressed or
cemented together.

20. • These sediments are moved by wind,
water, ice or gravity.
• Sedimentary rocks represent 7% of
the Earth’s crust, but they cover 70%
of the Earth’s surface.
• Sedimentary rocks are
fossil-carrying rocks.

21. What turns sediments into solid rock?
• Water or wind breaks down and
deposits sediment (erosion &
deposition)

22. • The heavy sediments press down on
the layers beneath (compaction)

23. Recognise this place in Egypt?

24. • Dissolved minerals flow between the
particles and cement (glue) them
together this is called cementation.

25. How can sedimentary layers help us
understand the age of fossils?
• As sedimentary rocks
are deposited, they
form horizontal
layers
• Scientists know that
the layers on top
(and the fossils in
the top layer) are
YOUNGER than the
fossils in lower
layers.

26. • Rocks that have changed due to
intense temperature and pressure
• “Meta” means “change” and morphosis
means “form” in Greek
• Igneous, sedimentary and other
metamorphic rocks can change to
become metamorphic rocks

27. What occurs in the Earth to
change these rocks?
• Pressure from rock layers on top of it
• High heat, but not enough to melt the rock
• Rocks may be flattened or bent or chemicals
may be exchanged to form new minerals.

28. Properties of metamorphic rocks
• Usually resistant to weathering and
erosion and are therefore very hard-
wearing.
• Can be polished to give a smooth shiny
surface.
• Example: Marble, slate.

29. Examples of rocks becoming
metamorphic
• Example: marble formed from limestone