petrology (geology for civil engineers)

1. PETROLOGY
CE 202
GEOLOGY FOR CIVIL ENGINEERS
Engr. GINALYN G. SUMAIT
Instructor

2. CLASSIFICATION OF
ROCKS

3. CLASSIFICATION OF ROCKS
1. IGNEOUS ROCKS
2. SEDIMENTARY ROCKS
3. METAMORPHIC ROCKS

4. IGNEOUS ROCKS

5. IGNEOUS ROCKS
• Igneous rocks form when magma, or melted rock from
inside the Earth, cools and hardens.
• They can form above ground when magma erupts from a
volcano as lava.
• They can also form deep inside the Earth's crust and then
be exposed at the surface by the overlying rocks wearing
away.
• The crystals found in igneous rocks have angular shapes.
• They have not been worn like sedimentary rocks or
squished like metamorphic rocks.

6. IGNEOUS ROCKS
Definition:
• rock that forms when magma cools, hardens, and crystallizes
Where it forms:
• on the Earth's surface or inside the Earth
Two types:
• intrusive or extrusive
Common examples:
• pumice, basalt, granite
Where it's found:
• on every continent and on the ocean floor
Cool fact:
• Volcanoes and most mountains are made of igneous rocks.

7. IGNEOUS ROCKS
Intrusive igneous rocks form from magma
that cools slowly underground.
Extrusive rocks form when magma erupts
from volcanoes.

8. IGNEOUS ROCKS
• Most of the Earth's crust is made of
igneous rocks.
• About 75% of the Earth's crust is made up
of igneous rocks.
• Basalt makes up most of the crust under
the sea.
• Granite makes up most of the continental
crust.

9. MOST COMMON
IGNEOUS ROCKS
• Granite
• Diorite
• Gabbro
• Dolerite
• Basalt

10. GRANITE
• A common type of
intrusive (plutonic) rocks.
• It is light color with pink
to grey color.
• This rock mainly consists of quartz, feldspar
and mica.
• used as the most important building stone for
the decorative, monumental, and
architectural purposes because of its light
color.

11. GABBRO
• It is coarse grained,
intrusive mafic igneous rock
which is chemically equivalent
to basalt.
• It is dark in color with grey to black.
• It is used as a road material and concrete
aggregate.
• It is also used in kitchen and their
countertops. Also widely used as graveyard
headstone.

12. BASALT
• Basalt is common extrusive
(volcanic) rock formed by the
rapid cooling of lava.
• It is usually grey to black in color.
• It has fine-grained mineral texture.
• It is used in construction (as building
blocks or in groundwork) It is also used
in construction of bridges, making
cobblestones, and making statues.

13. DIORITE
• an intrusive igneous rock
and an extremely hard rock
• It is grey to dark grey in color. It can also be
black or bluish grey.
• Its hardness is to be worked finely and take
a high polish to provide a durable finished
work.

14. DOLERITE
• is mafic, holocrystalline,
subvolcanic rock
• also known as diabase and has a dark
brown color.
• used as crushed stone and as ornamental
stone.

15. SEDIMENTARY
ROCKS

16. SEDIMENTARY ROCKS
• formed through the deposition and solidification of
sediment, especially sediment transported by water
(rivers, lakes, and oceans), ice (glaciers), and wind.
• includes a wide variety of rocks formed by accumulation,
compaction and consolidation of sediments.
• sediments may be defined as particles produced from the
decay and weathering of pre- existing rocks or may be
derived from remains of dead sea or land animals in
suitable environments
• accumulation and compaction of these sediments
commonly takes place under water or at least in the
presence of water.

17. SEDIMENTARY ROCKS
. A series of well-defined steps are involved in the formation of clastic
rocks.
1. Decay and Disintegration
2. Transport of Sediments
3. Gradual Deposition
4. Diagenesis - The process of transformation of loose sediments
deposited in the settlement basins to solid cohesive rock masses
either under pressure or because of cementation is collectively
known as diagenesis. It may be achieved by either of the two
methods:
• Welding (compaction) - is the process of compaction of the sediments
accumulated in lower layers of a basin due to the pressure exerted
by the load of the overlying sediments.
• Cementation - is the process by which loose grains or sediments in a
settlement basin get held together by a binding material.

18. SEDIMENTARY ROCKS
Name Origin:
comes from the Latin sedimentum, which means "act of
settling"
Description:
When rocks weather, they break down into little bits.
After a very long time, these tiny particles can get pressed
together to form new rocks.
Significance:
These rocks provide the most clues about the history of
life on Earth.
On Earth's surface, sedimentary is the most common
type of rock.

19. MOST COMMON
SEDIMENTARY ROCKS
• Sandstone
• Limestone
• Shale
• Conglomerate
• Breccia

20. SANDSTONES
• Sandstones are mechanically formed
sedimentary rocks of Arenaceous Group.
• These are mostly composed of sand grade
particles that have been compacted and consolidated
together in the form of beds in basins of sedimentation.
• The component grains of sandstones generally range in
size between 2mm and 1/16 mm. Silica in the form of
very resistant mineral QUARTZ is the dominant
mineral constituent of most sandstones.

21. LIMESTONES
• These are the most common sedimentary rocks from the
non-clastic-group and are composed chiefly of carbonate of
calcium with subordinate proportions of carbonate of
magnesium.
• They are formed both bio-chemically and mechanically.

22. SHALE
• is a fine-grained sedimentary rock of argillaceous (clayey)
composition.
• are generally characterized with a distinct fossility (parting)
parallel to the bedding planes and are made up of very fine
particles of silt grade and to some extent of clay.
• Besides fossility, some shales show the laminated structure.

23. CONGLOMERATES
• Clastic in nature and also belong to rudaceous group.
• consist mostly of rounded fragments of various sizes but
generally above 2mm. cemented together in clayey or
ferruginous or mixed matrix.
• The roundness of gravels making the rock is a useful
characteristic to differentiate it from breccia in which the
fragments are essentially angular.

24. CONGLOMERATES
On the basis of the dominant grade of the constituent gravels
in following three types:
• Boulder-Conglomerates (gravels> 256mm)
• Cobble-Conglomerate (gravels: 64-256 mm)
• Pebble-Conglomerate (gravels: 2-64 mm)

25. CONGLOMERATES
On the basis of source of the gravels:
• Basal-conglomerates – gravels derived
from advancing sea-waves over subsiding land masses
• Glacial-conglomerates – gravel making the conglomerates
are distinctly of glacial origin
• Volcanic-conglomerates – gravels are of distinct volcanic
origin but have subsequently been subjected to lot of
transport resulting in their smoothening and polishing by
river transport before their deposition and compaction or
cementation.

26. BRECCIA
• mechanically formed sedimentary
rock classed as Rudite.
• consists of angular fragments of heterogeneous
composition embedded in a fine matrix of clayey material.
• fragments making breccia are greater than 2mm average
diameter but sometimes these may be quite big in
dimensions.
• angularity of the fragments indicates that these have
suffered very little or even no transport after their
disintegration from the parent rocks.

27. BASAL BRECCIA
• formed by the sea waters advancing over a coastal region
covered with fragments of chert and other similar rocks.
• advancing waters supply the fine mud, which is spread over
the rock fragments and acts as a binding material.
• Once the seawater retreats, the loose chert fragments get
cemented together as breccia rocks.

28. FAULT BRECCIA
• This rock is also called crush-breccia. Such rocks are so
named because they are made up of angular fragments that
have been produced during the process of faulting.

29. AGGLOMERATIVE BRECCIA
• It is a specific type of breccia containing angular and sub
angular fragments derived from volcanic eruptions.
• It may also contain some fused material that has been
cemented together with the solid material broken and
thrown out of the craters.

30. METAMORPHIC
ROCKS

31. METAMORPHIC ROCKS
• Metamorphic rock is the result of the transformation of an
existing rock type, the protolith, in a process called
metamorphism.
• The protolith is subjected to heat and pressure causing
profound physical and chemical change.
• The protolith may be sedimentary rock, igneous rock, or
another (older) metamorphic rock.
Metamorphism – the change of mineral or geologic texture in
pre-existing rocks occurs primarily due to heat, pressure and
the introduction of chemically active fluids changes at or just
beneath Earth’s surface due to weathering and/or diagenesis are
not classified as metamorphism typically occurs between
diagenesis 200oC and melting 850oC.

32. METAMORPHIC ROCKS
Definition:
rock that changes from heat and pressure
Where it forms:
usually deep within the Earth's crust where it is hot
and pressures are high
Common examples:
marble, slate, schist
Cool fact:
The mantle is made entirely of metamorphic rock.

33. METAMORPHIC ROCKS
• The word "metamorphic" comes from the Greek word
morphe, which means "form," and meta, meaning change.
• Metamorphic means "to change form"-which is exactly what
metamorphic rocks do. The heat and pressure change
everything: their texture, color, grain size, and the shapes
and even the types of their crystals.
• Metamorphic rocks are likely to be found deep under the
Earth's mountains. That is where rocks are crushed, folded,
and squeezed by the movement of the Earth's tectonic
plates.
• Metamorphic rocks can also form from other metamorphic
rocks. In the rock cycle, every kind of rock can be turned
into another kind of rock.
• The heat and pressure actually make the rock stronger.
When limestone becomes the metamorphic rock marble, it
becomes much more durable.

34. MOST COMMON
METAMORPHIC ROCKS
• Quartzite
• Marble
• Slate
• Gniess
• Schists

35. QUARTZITE
• are granular metamorphic rocks composed chiefly of inter
sutured grains of quartz.
USES: The rock is generally very hard, strong, dense and
uniformly grained. It finds extensive use in building and road
construction.

36. MARBLE
• is essentially a granular metamorphic
rock composed chiefly of recrystallized
limestone (made of mineral calcite).
USES: Marble is commonly used in the construction of palatial
and monumental buildings in the form of blocks, slabs, arches
and in the crushed form as chips for flooring.Because of its
restricted occurrence and transport costs, it is mostly used as
ornamental stone in costly construction.

37. SLATE
• is an extremely fine-grained metamorphic rock
characterized by a slate cleavage by virtue of which it can
be readily split into thin sheets having parallel smooth
surfaces.
USE: Slate is used locally (where available) for construction
purpose as a roofing and paving material only.

38. GNIESS
• is a megascopically crystalline foliated metamorphic rock
characterized by segregation of constituent minerals into
layers or bands of contrasting color, texture and
composition.
USE: Compact, dense and massive varieties of gneisses find
applications as road stones and in some cases as building
stones.

39. SCHIST
• are megascopically crystalline foliated metamorphic rocks
characterized by a typical schistose structure.
• The constituent flaky and platy minerals are mostly
arranged in parallel or sub parallel layers or bands