earth, faults, hazards

1. GEOLOGY

2. What is Geology?
EARTH STUDY OF DISCOURSE
gē -logiaGreek
word
is an earth science comprising the study
of solid Earth, the rocks of which it is
composed, and the processes by which they
change.
Earth science or geoscience is an all-
encompassing term that refers to the fields
of science dealing with planet Earth.

3. Why Study the Earth?
• We're part of it. Dust to Dust. Humans have the capability to make rapid changes. All
construction from houses to roads to dams are effected by the Earth, and thus require
some geologic knowledge. All life depends on the Earth for food and nourishment. The
Earth is there everyday of our lives.
• Energy and Mineral resources that we depend on for our lifestyle come from the Earth.
At present no other source is available.
• Geologic Hazards -- Earthquakes, volcanic eruptions, hurricanes, landslides, could
affect us at any time. A better understanding of the Earth is necessary to prepare for
these eventualities.
• Curiosity-- We have a better understanding of things happening around us. Science in
general. I'll try to relate geology (and science in general) to our everyday lives.

4. • The Earth -- What is it?
• Density, (mass/volume), Temperature, and Pressure increase with depth.
Earth has layered
structure. Layering can
be viewed in two
different ways:
1. Layers of different
chemical composition
2. Layers of differing
physical properties.
WHAT ARE THE LAYERS OF THE EARTH?

5. 1. Compositional Layering
Crust - variable thickness and composition
• Continental 10 - 70 km thick - "granitic" (made mostly of Oxygen
and Silicon) in composition
• Oceanic 2 - 10 km thick - "basaltic" (less Silicon than in
continental crust, more Magnesium)
Mantle - 3488 km thick, made up of a rock called peridotite. Solid
but can deform so that it confects (moves in response to
temperature differences).
Core - 2883 km radius, made up of Iron (Fe) and small amount of
Nickel (Ni)

6. 2. Layers of Differing Physical Properties
Lithosphere - about 100 km thick (deeper beneath continents)
Asthenosphere - about 250 km thick to depth of 350 km - solid rock,
but soft andflows easily.
Mesosphere - about 2500 km thick, solid rock, but still capable of
flowing.
Outer Core - 2250 km thick, Fe and Ni, liquid
Inner core - 1230 km radius, Fe and Ni, solid

7. Composition of the Earth
• The bulk chemical composition of the Earth is mostly Iron (Fe, 34.6%),
Oxygen (O2, 29.5%), Silicon (Si, 15.2%), and Magnesium (Mg, 12.7%),
with other elements making up the other 8%. These elements are
distributed unevenly due to the layering, with Fe being concentrated
in the core, Si, O2, and Mg being concentrated in the mantle, and Si,
O2, and the other elements being concentrated in the thin veneer of
the crust.

8. GOING BACK TO
THE BASIC diameter of the earth at the equator-
7,926.41 miles (12,756.32 kilometers)
Diameter of the earth at the poles- 7,901
miles (12,715.43 kilometers)
Thus;
-the earth is a tad wider 41kilometers than
it’s tall.
-diameter taken in poles is a bit shorter
than diameter taken in its equator.

9. Rock Cycle

10. Igneous rock
Intrusive (plutonic rocks) Extrusive (volcanic rocks)
- are rocks formed when magma
cools and solidifies below the
earth's surface
-The term originated from Pluto,
the classical god of the
underworld
-are rocks formed when lava
cools and solidifies on the
earth's surface.
DIFFERENCES
-crystals of volcanic rocks are
so small that you can only see
them with a microscope.
-When lava meets the cooler
temperatures of the
atmosphere, it cools rapidly
and solid crystals form
-because of the rapid cooling
this crystallization happens too
fast for the crystals to grow
very big.
-plutonic rocks cool much slower
and under higher pressure
because they are in the ground.
-their crystals have the right
conditions to grow large.
-plutonic rocks have coarse-
grained crystals.
-Because magma is under high
pressure and takes a long time to
cool, it allows time for the
formation of large crystals.

11. Extrusive volcanic Igneous rocks

12. Intrusive Plutonic rocks
The most common rock types in plutons
are granite, granodiorite, tonalite,monzonite, and quartz diorite. Generally light
colored, coarse-grained plutons of these compositions are referred to as granitoids.
granodiorite
tonalite
monzonite
Quartz diorite

13. What is pluton?
a pluton is a body of intrusive igneous rock (called a plutonic rock) that is crystallized
from magma slowly cooling below the surface of the Earth. Plutons
include batholiths, stocks, dikes, sills, laccoliths, lopoliths, and other igneous bodies. In practice,
"pluton" usually refers to a distinctive mass of igneous rock, typically several kilometers in dimension,
without a tabular shape like those of dikes and sills. Batholiths commonly are aggregations of plutons.
What is Batholith?
A batholith (from Greek bathos, depth
+ lithos, rock) is a large emplacement of
igneous intrusive (also called plutonic)
rock that forms from cooled magma deep
in the Earth's crust. Batholiths are almost
always made mostly of felsic or
intermediate rock-types, such
as granite, quartz monzonite, or diorite

14. SILL VS DIKE
-Sills parallel beds (layers)
and foliations in the
surrounding country rock.
They can be originally
emplaced in a horizontal
orientation, although
tectonic processes may
cause subsequent rotation
of horizontal sills into near
vertical orientations.
-Sills are fed by dikes, except
in unusual locations where
they form in nearly vertical
beds attached directly to a
magma source.
-A dike or dyke in
geological usage is a
sheet of rock that
formed in
a fracture in a pre-
existing rock body
-vertical in
appearance

15. But what is laccolith?
A laccolith is a sheet intrusion (or concordant pluton)
that has been injected between two layers
of sedimentary rock. The pressure of the magma is
high enough that the overlying strata are forced
upward, giving the laccolith a dome or mushroom-like
form with a generally planar base.
Laccoliths tend to form at relatively shallow depths and
are typically formed by relatively viscous magmas, such as
those that crystallize to diorite, granodiorite, and granite.
Cooling underground takes place slowly, giving time for
larger crystals to form in the cooling magma. The
surface rock above laccoliths often erodes away
completely, leaving the core mound of igneous rock. The
term was first applied as laccolite by Grove Karl Gilbert
after his study of intrusions of diorite in the Henry
Mountains of Utah in about 1875 (see image below)

16. How about the lopolith? A lopolith is a
large igneous intrusion which
is lenticular in shape with a
depressed central region.
Lopoliths are generally
concordant with the
intruded strata with dike or
funnel-shaped feeder bodies
below the body.
LOPOLITH VS LACCOLITH

17. Convection current
Mantle convection is the slow creeping motion
of Earth's rocky mantle caused by convection
currents carrying heat from the interior of the
earth to the surface.
Convection is one of the three
main types of heat transfer, the
other two being conduction
and radiation. Unlike the other
two, convection can only happen
in fluids -- liquids and gases. This is
because the molecules have to be
free to move.

19. Tectonic plates/Plate tectonics (from
the Late Latin tectonicus, from
the Greek:τεκτονικός "pertaining to
building")
Tectonic plates are pieces of Earth's
crust and uppermost mantle, together
referred to as the lithosphere. The
plates are around 100 km (62 mi)
thick and consist of two principal
types of material: oceanic crust (also
called sima from silicon and magnesiu
m) and continental crust (sial from
silicon and aluminium).
PLATES

20. How many plate tectonics do we have?
Actually there are about 63 and still counting, but for
the purpose of the list, let me divide the plates into
three. The major, minor, and microplates.

21. TECTONIC PLATES
MAJOR OR PRIMARY PLATES MINOR OR SECONDARY PLATES MICROPLATES OR TERTIARY PLATES
a major plate is any plate
with an area greater than
10 million km2.
a minor plate is any plate
with an area less than 10
million km2 but greater than
1 million km2.
a microplate is any
plate with an area less
than 1 million km2
Nazca Plate – 5,500,000 km2
Philippine Sea Plate – 5,500,000 km2
Arabian Plate – 5,000,000 km2
Caribbean Plate – 3,300,000 km2
Cocos Plate – 2,900,000 km2
Caroline Plate – 1,700,000 km2
Scotia Plate – 1,600,000 km2
Burma Plate – 1,100,000 km2
New Hebrides Plate – 1,100,000 km2
Pacific Plate – 103,300,000 km2
North American Plate – 75,900,000 km2
Eurasian Plate – 67,800,000 km2
African Plate – 61,300,000 km2
Antarctic Plate – 60,900,000 km2
Indo-Australian Plate – 58,000,000 km2
South American Plate – 43,600,000 km2
Philippine Sea Plate
Mariana Plate
Philippine Microplate

22. PLATE BOUNDARIES
1. Transform
2. Divergent
3. Convergent

25. FAULTS!

37. LANDSLIDE