The document describes the three main types of rocks - igneous, sedimentary, and metamorphic. It explains that igneous rocks form from the cooling of magma, sedimentary rocks form from the compaction of sediments, and metamorphic rocks form from the alteration of existing rocks due to heat and pressure. The rock cycle is also discussed, which illustrates how rocks continuously form, change, and erode over time. Various sub-types and characteristics of each rock type are provided as examples.

1. Rocks
Unit 3

2. 2.1 The Rock Cycle
•Rocks – a naturally occurring solid
collection of one or more minerals.
•Three Major Types of Rock
• Igneous Rock
• Sedimentary Rock
• Metamorphic Rock

3. 2.1 The Rock Cycle
•Igneous Rock – rocks that forms when
magma cools and solidifies.

4. 2.1 The Rock Cycle
•Sedimentary Rock – rocks formed by the
compaction and cementation of
sediments.

5. 2.1 The Rock Cycle
•Metamorphic Rock – rocks formed when
existing rock is changed by heat and/or
pressure.

6. 2.1 The Rock Cycle
•Rock Cycle – shows the processes in which
rocks form, are destroyed, and form again.

7. 2.1 The Rock Cycle
•Much of the rock in Earth’s crust has
passed through the rock cycle many times,
but some rock does not pass through each
stage in the rock cycle.

8. 2.2 Igneous Rocks
•Igneous Rock – rocks that forms when
magma or lava cools and solidifies.

9. 2.2 Igneous Rocks
•Identity of an igneous rock is determined by…
• the chemical composition of minerals in the rock.
• Felsic = rich in feldspar and silica = lighter color
• Mafic = rich in magnesium and iron = darker color
• the rock’s texture.
• Fine grained
• Coarse grained

10. 2.2 Igneous Rocks
•Magma forms when rock melts.
•Three factors that cause a rock to melt.
• Temperature
• Pressure
• Presence of fluids in the rock

11. 2.2 Igneous Rocks
•Igneous rocks are classified according to
where the magma cools and hardens.
• Intrusive Igneous Rock
• Extrusive Igneous Rock

12. 2.2 Igneous Rocks
•Intrusive Igneous Rock – rock that cools
deep inside the crust.

13. 2.2 Igneous Rocks
•Extrusive Igneous Rock – lava that cools
at Earth’s surface.

14. 2.2 Igneous Rocks
•Igneous rocks are also classified according
to the texture and crystal size.

15. 2.2 Igneous Rocks
•Course Grained Texture
• Intrusive igneous rocks
normally have large
crystals because they
cool very slowly within
the Earth.
• Granite

16. 2.2 Igneous Rocks
•Fine Grained Texture
• Extrusive igneous rocks
normally have small
mineral grains too small
to see.
• Basalt, Rhyolite

17. 2.2 Igneous Rocks
•Porphyritic Texture
• Both large and small crystals
• Diorite, Porphyritic Granite

18. 2.2 Igneous Rocks
•Glassy Texture
• When magma cools
quickly few crystals are
able to grow and a glassy
texture forms.
• Obsidian

19. 2.2 Igneous Rocks
•Vesicular (Porous) Texture
• If there are a lot of dissolved
gases in the magma and the
magma cools rapidly this can
produce a rock full of holes,
or vesicles.
• Scoria, Pumice

20. 2.2 Igneous Rocks

21. 2.3 Sedimentary Rocks
•Sedimentary Rock – rocks formed by the
compaction and cementation of
sediments.

22. 2.3 Sedimentary Rocks
•Sediments – loose fragments of rock,
minerals and organic material that result
from the breakdown of rock by
weathering.

23. 2.3 Sedimentary Rocks
•Processes that convert loose sediment to
sedimentary rock…
• Weathering
• Erosion

24. 2.3 Sedimentary Rocks
•Weathering – when wind and water break
rock down into smaller pieces, or sediment.

25. 2.3 Sedimentary Rocks
•Erosion – the movement of sediments by
wind, water, gravity, or other natural
forces.

26. 2.3 Sedimentary Rocks
•Deposition – the depositing and
accumulation of sediment in an area.

27. 2.3 Sedimentary Rocks
•Compaction – the process in which
sediment is squeezed and the space in
between grains is reduced by the weight
of the overlying layers.

28. 2.3 Sedimentary Rocks
•Cementation – the process in which
sediments are glued together by minerals
as water evaporates.

29. 2.3 Sedimentary Rocks
•Types of sedimentary rocks are
determined by processes in which the
rocks form and their composition.
• Chemical Sedimentary Rock (CSR)
• Organic Sedimentary Rock (OSR)
• Clastic Sedimentary Rock (CSR)

30. 2.3 Sedimentary Rocks
•Chemical Sedimentary Rock (CSR) – forms
from minerals that were dissolved in
water and as water evaporates minerals
are left behind.
• rock salt, gypsum, dolomitic limestone,
stalactites, and stalagmites

31. 2.3 Sedimentary Rocks
•Organic Sedimentary Rock (OSR) – forms
from the remains of living things.
• coal, chalk, and shell limestone
Coquina, made with shells

32. 2.3 Sedimentary Rocks
•Clastic Sedimentary Rock (CSR) – formed
by rock fragments that are carried away
from their source by water, wind, and ice
and are compressed and glued together
by minerals.
• Groups of CSR based on the size of the
sediments
• Conglomerates: large grains
• Sandstones: sand sized grains
• Shales: fine grained

33. 2.3 Sedimentary Rocks

34. 2.3 Sedimentary Rocks

35. 2.3 Sedimentary Rocks

36. 2.4 Metamorphic Rocks
•Metamorphic Rock – rocks formed when
existing rock is changed by heat and/or
pressure.
•Metamorphism – the process in which
heat, pressure, and chemical processes
change existing rock.

37. 2.4 Metamorphic Rocks
•Types of Metamorphism
• Contact Metamorphism
• Regional Metamorphism

38. 2.4 Metamorphic Rocks
•Contact Metamorphism – a change in the
texture, structure, or chemical composition of
a rock due to contact with magma.
• Only a small area of rock is changed by the heat.
• Often occurs near volcanoes.

39. 2.4 Metamorphic Rocks
• Regional Metamorphism – a change in the
texture, structure, or chemical composition
or a rock due to changes in temperature
and pressure over a large area.
• Large area of rock is changed.
• Result of tectonic movement.

40. 2.4 Metamorphic Rocks
•Metamorphic Rock Classification
• Foliated Rocks
• Nonfoliated Rocks

41. 2.4 Metamorphic Rocks
•Foliated Rocks – occurs when rocks are
arranged into bands under great pressure
and some heat.
• Slate, Schist, Gneiss

42. 2.4 Metamorphic Rocks
•Nonfoliated Rocks – rocks that do not
have bands because they formed under
little pressure and great heat.
• Rock does not melt
• Marble

43. 2.4 Metamorphic Rocks

44. 2.4 Metamorphic Rocks