Geology

Geology
27th June 2008

VENKAT M.
PlotMaker
QA-Minex

GEOLOGY
GEO – Earth
LOGUS – Speech/Study
Geology – Study of earth

James Hutton, the Scottish geologist, naturalist, chemist
and experimental farmer, is the father of modern geology.

27 August 2010 Copyright 2007, Gemcom Software International Inc.

Earth
The Crust The thin skin of Earth - 3 to 40 miles
thick.

The Mantle This deep layer of warm rock accounts
for two-thirds of the mass of our planet.

The Outer Core Made of molten iron, nickel, and
other ingredients yet to be determined. Streaming
at possibly one to several miles per week.

The Inner Core a ball of iron alloy one-third the
size of the moon in the center of earth. This metal
ball is broiling hot at 11,000 degrees Fahrenheit,
comparable to the surface of the sun, but it
remains solid because of the enormous weight of
all the rest of Earth bearing down on it.


Earth - Magnet

The rotational forces of the liquid
iron are reasonable for the earths
magnetism.

So, there is true and magnetic
north due to the tilt in the axis of
rotation of the earth.

The angle between true and
magnetic north is called
Declination.


Plate Tectonics

• The Earth's surface is made up of a
series of large plates (like pieces of a
giant jigsaw puzzle).
• These plates are in constant motion
travelling at a few centimeters per
year.
• Convection currents beneath the
plates move the plates in different
directions.
• The source of heat driving the
convection currents is radioactive
decay which is happening deep in
the Earth.


Plate Tectonics A Small Video


Geological
Time Scale
• The geological time scale is used by
geologists and other scientists to
describe the timing and relationships
between events that have occurred
during the history of Earth.

• The vast expanse of geological time
has been separated into eras,
periods, and epochs.

• Younger formations are on top and
as we go down in GTS we will get the
older formations and between each
formation there is a unconfirmity.


Mineral
A Naturally occurring
•
Founded in nature, not synthetic.

• Solid crystalline substance Composed of atoms arranged in
an orderly, repeating, 3-D array.
• Generally inorganic
Formed independently of
• With a specific chemical plants and animals (organic
material - carbon).
composition.

Unique combination and arrangement of
atoms: can be represented with a chemical
formula.


Minerals
Examples: Gold, iron, copper, salt, diamonds,
feldspar, calcium, phosphorus, etc.

Feldspar Gold
Iron


Rocks

More than one kind of
mineral stuck together
forms a ROCK.
ROCK.


Rocks - Types

Igneous

Sedimentary

Metamorphic


Rocks - IGNEOUS
• Deep inside the Earth, rocks and minerals melt under tremendous
heat. This forms magma.

• When the magma cools back down, it hardens and forms new
rocks. These rocks are called IGNEOUS rocks.


Rocks - IGNEOUS

INTRUSIVE
EXTRUSIVE Magma cools slowly over
Forms from molten rock
Forms when lava cools cooling and solidifying millions of years deep
quickly on the Earths beneath the surface –
surface results in Crystalline
formations


Rocks - IGNEOUS


Rocks - IGNEOUS
These BASALT columns near Fingal’s
Cave form the base of the Scottish
island of Staffa. The columns formed
when cooling lava flows met bedrock
and the region’s cold weather.


Rocks - IGNEOUS
Mount Rushmore - Keystone, South Dakota


Rocks - IGNEOUS

BASALT – Extrusive igneous rock GRANITE – Intrusive igneous rock


Rocks - SEDIMENTARY

Weathering and
Transportation Deposition
Erosion

Compaction and Sedimentary
Cementation Rock


Rocks - SEDIMENTARY
Sedimentary rocks are divided into two categories

Chemical Clastic

Mineral are dissolved in to the water…water is Made from eroded
evaporated off and leaves behind chemical fragments of other rocks
sedimentary rocks

Shale
Examples - Limestone & Gypsum
Sandstone

Conglomerate


Rocks - SEDIMENTARY

Sandstone Limestone Shale Conglomerate


Rocks - SEDIMENTARY
Bryce Canyon, Utah.
The sea dried up, the sandstone was uplifted to form a vast plateau.
The Paria River eroded the layers to form the spectacular scenery.


Rocks - SEDIMENTARY


Rocks - SEDIMENTARY

Hatshepsut Temple, Luxor, Egypt.
This Temple was carved directly from the limestone cliff walls.


Rocks - METAMORPHIC
Meta – Change , Morphos - Shape , Metamorphic – Change in shape or form

• When rocks are subjected to
greater heat and pressure inside
the Earth, they are changed into
rocks which are different from the
original.

• This change occurs while the
original rocks are still in a solid
state.

• Thus the new rocks formed are
called metamorphic rocks.


Rocks - METAMORPHIC

Two types of
metamorphism

Contact Regional

Rock surrounding
Metamorphism
a magma body get
Tectonic forces occurs over a large
cooked and
area
changes due


Rocks - METAMORPHIC


Rocks - METAMORPHIC
Parent Rock Metamorphic Rock
Granite Gneiss

Shale Slate

Sandstone Quartzite


Rocks - METAMORPHIC
Michelangelo's Pieta

• Made of marble resulted from
the metamorphism by heat of
limestone or dolomite.

• Usually whitish but can be
found in other colours due to
impurities.


Rocks - METAMORPHIC

Mt Arapiles, Australia is
a world famous rock
climbing site.

Mountain is quartzite.


Rocks - METAMORPHIC
TAJ MAHAL
Finished in 1648 with Red sandstone base.
Marble walls inlaid with semiprecious gems.


Rock
Cycle


Coal is formed by the decomposition of
organic (vegetable) matter under high
pressure and heat. It is neither Mineral
heat.
nor Rock but it’s a fossil fuel.
fuel.


Coal – Stages of
Formation

PEAT LIGNITE BITUMINOUS ANTHRACITE


Geological
Map of INDIA


Strike - Dip

• Strike – A horizontal line used to represent the orientation/direction/trend
of the beds.
• Dip – It is the angle from horizontal in which the beds are lying.


Fault & Fold
• Fault (def)- a break in a body of rock along
which some displacement has occurred.

• Fold (def)- a bend in a body of rock, which is
generally being squeezed.


Fault & Fold - Mechanism

F
O
L
D

F
A
U
L
T

Fault – Normal Fault

• Normal Faults are produced by tensional forces.
• The upper block (Hanging wall) moves down to the lower
block (Foot wall).


Fault – Reverse Fault

• Reverse Faults are produced by Compressive forces.
• The upper block (Hanging wall) moves up relative to the lower
block (Foot wall).


Fault – Strike Fault

• Strike Faults are produced by shearing forces.
• The movement of the blocks is along strike direction.


San Andreas Fault, California
Fault –
Strike Fault


Fold – Terminology


Fold – Anticline

Anticlines are folds where the originally horizontal strata has been folded
upward, and the two limbs of the fold dip away from the hinge of the fold


Fold –Syncline

• Synclines are folds where the originally horizontal strata have been folded
downward, and the two limbs of the fold dip inward toward the hinge of the fold.
• Synclines and anticlines usually occur together such that the limb of a syncline is
also the limb of an anticline.

Folds


Few more Geological Terms…


Bedrock - The general term referring to the rock
underlying other unconsolidated material, i.e. soil.

Sills and dykes are formed when magma intrudes into rock. Sills form where magma
intrudes between layers, they run parallel to the layer. Dykes form when magma intrudes
into a rock along lines of weakness such as fractures and fissures. Dykes cut beds and
range in size from a few cm to several km.


Outcrop – Any place where bedrock/seam is visible on the
surface of the earth.
earth.


Intrusion – A sudden
appearance of different
rock in the middle of
other rock formation.


Questions…
Please

Finally…


Geology

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