This document discusses the three main types of rocks: igneous, sedimentary, and metamorphic. It provides details on their formation processes. Igneous rocks form from cooling magma, either underground (intrusive) or above ground (extrusive). Sedimentary rocks form through the compaction and cementation of sediments. Metamorphic rocks form from changes to existing rocks through heat and pressure in the crust. The rock cycle model describes how rocks continuously change between these three types through geological processes over millions of years.

1. ROCKS AND THE
ROCK CYCLE

2. PETROLOGY
Scientific study of rocks

3. The Earth as a “rock”
• The Earth is a solid
rock with a depth of
2900 kilometers,
where mantle meets
the outer core

4. Rocks
•Formed from aggregation
of one or more minerals
and other substances that
are cohered into a solid
structure.

5. Classification of Rocks
Igneous Sedimentary Metamorphic

6. IGNEOUS
ROCKS
From the word
“ignis/ignus”
which means
fire

7. Igneous Rocks
Crystalline
Formed from cooled magma or
lava
• Intrusive and Extrusive Rocks
Pyroclastic
Formed from consolidated
eruption products like volcanic
ash.

8. Crystalline Igneous Rock
Plutonic/Intrusive
Extrusive

9. Extrusive/Volcanic
rock
• forms when magma makes
its way to Earth’s surface
• as lava and then cools.
The crystals are very small
(fine grained) since the
cooling process is fast.

10. Extrusive Igneous
Rocks

11. Extrusive Igneous Rocks
•Glassy and fine texture due to
the fast-cooling process, crystal
formations are small and spread
out

12. Intrusive/Plutonic
FORMED FROM SLOWLY
COOLED MAGMA
FORMED BENEATH THE
EARTH
HAVE VERY LARGE
CRYSTALS

13. Intrusive/Plutonic Rocks
Gabbro and Granite
This Photo by Unknown Author is licensed under CC BY
This Photo by Unknown Author is licensed under CC BY

14. Pyroclastic Rocks
• Formed on the surface,
from consolidation of
particle erupted by
explosive volcanic
activity
This Photo by Unknown Author is licensed under CC BY

15. Color index of Igneous
Rocks
FELSIC
COMPOSITION
-light colors
-rich in silica
MAFIC
COMPOSITION
-dark colors
-poor in silica
but rich in iron
and
magnesium
INTERMEDIATE
COMPOSITION
-have an
intermediate
color
-gray or
consisting of
equal parts of
dark and light
mineral
ULTRAMAFIC –
very dark in
color

16. TEXTURE OF
IGNEOUS ROCKS

17. Textures
Phaneritic
Phaneros-visible
Crystals are visible to the eye without
the aid of magnifying lens/Coarse
grained
Pegmatitic
When minerals crystallize very slowly
Composed of very large crystals
(larger than 2 to 3 cm)

18. Aphanistic
Aphaneros- invisible
Fine grained, crystals cannot be
distinguished without the use of
magnifying tools
Porphyritic
Combination of fine and large crystals
Glassy
Non-ordered solid from rapid
quenching

22. SEDIMENTARY
ROCKS
“Sandwiched
Rocks”

23. • For millions of years the
earth’s surface have been
broken down by wind,
water, and other agents
into smaller particles
known as “sediments”

24. Sedimentary Rocks
⚫ Particles of sand, shells, pebbles, and
other fragments of materials called
sediments, accumulate in layers and over
long period of time harden into rocks.
⚫ Compaction-due to increase of pressure
of layered sediments it bind together to
form the sedimentary rocks.

25. Formation of
Sedimentary
Rocks
Erosion – wind, water and other agents
carry away sediments
Deposition – sediments are carried by
bodies of water where they settle at the
bottom
Compaction – as more layers piled up the
layers are smashed together therefore
compacting it
Lithification - complex process whereby
freshly deposited loose grains of sediment
are converted into rock.
https://www.britannic
a.com/science/lithificat
ion

26. SEDIMENTARY ROCKS
CLASTIC
-from the cementation
of sediments that have
been deposited, buried,
and compacted over a
long period of time
Examples: conglomerate,
breccia, sandstone, shale
CHEMICAL
SEDIMENTARY ROCKS
-from the precipitation
of minerals from ion
solutions
Halite - formed when a
body of seawater
becomes closed off and
evaporates.
BIOCLASTIC/ORGANIC
-from the compaction
and cementation of
plants/animal remains
Coal - composed of
organic matter in the
form of plants fragments

27. Sedimentary Rocks

28. METAMORPHIC
ROCKS
Changing
Rocks

29. Metamorphic rocks
• These rocks are
morphed or changed
into a different type of
rocks. Metamorphic
means to change in form.
It can be previously be
igneous, sedimentary, or
another metamorphic
rock

30. Types of metamorphism
Regional-due to changes in pressure and
temperature over large region of the crust
Contact-mainly by heat due to contact
with magma

32. Classification:
a. Texture - refers to the size arrangement ad grains within the
rock.
b. Foliation - any planar arrangement of mineral grains or
structural features within the rock. *foliated - appeared banded
or layered, contains crystals Example: mica
• Non-foliated - made up of only few minerals

33. Foliated Metamorphic
Rocks
• Due to temperature and pressure
minerals are aligned thus
creating a banded appearance
similar to pages of a book
• Example-gneiss
This Photo by Unknown Author is licensed under CC BY

34. Non-Foliated
Metamorphic Rock
• Do not show layers and are made
up of only few minerals and
shows almost a consistent
appearance all throughout.
• Example: Marble

35. Foliation will
manifest
physically in
the rock’s
tendency to
separate
along
parallel
planes.
If minerals
are barely
visible to the
naked eye,
their
alignment
results in
obvious but
not clearly-
defined
foliation.
If minerals
are visible to
the naked
eye, their
layering is
more distinct.
If the
minerals are
visible and
elongated,
the rock
exhibit a
coarsely-
branded
appearance
due to
alignment of
minerals.

37. ROCK CYCLE
-Model that describes all
the processes by which
rocks are formed,
modified, transported,
decomposed, melted and
reformed.