Download GEOLOGY FOR MINING ENGINEERS

GEOLOGY FOR MINING ENGINEERS
Prof.Dr.Kadir DİRİK
Lecture Notes
2017
THE SCIENCE OF GEOLOGY
GEOLOGY is the study of the Earth, including the materials that it is
made of, the physical and chemical changes that occur on its surface
and in its interior, and the history of the planet and its life forms.
Most of the Earth is solid rock, surrounded by the hydrosphere, the biosphere, and
Prof.Dr.Kadir Dirik Lecture Notes
the atmosphere.
Most of the Earth is composed of rocks. Rocks, in turn, are composed
of minerals
Prof.Dr.Kadir Dirik Lecture Notes
Most of the Earth is solid rock, surrounded by the hydrosphere, the
biosphere, and the atmosphere. Although more than 3500 different
minerals exist, fewer than a dozen are common. We study the origins,
properties, and compositions of both rocks and minerals.
There are two processes acting on the earth namely internal and
external processes
INTERNAL PROCESSES
Processes that originate deep in the Earth’s interior are called internal
processes. These are the driving forces that raise mountains, cause
earthquakes, and produce volcanic eruptions.
SURFACE PROCESSES
Surface processes are all of those processes that sculpt the Earth’s
surface. Most surface processes are driven by water, although wind,
ice, and gravity are also significant.
Prof.Dr.Kadir Dirik Lecture Notes
UNIFORMITARIANISM AND CATASTROPHISM
James Hutton was a gentleman farmer who lived in Scotland in the
late 1700s. Although trained as a physician, he never practiced
medicine and, instead, turned to geology. Hutton observed that a
certain type of rock, called sandstone, is composed of sand grains
cemented together. He also noted that rocks slowly decompose into
sand, and that streams carry sand into the lowlands. He inferred that
sandstone is composed of sand grains that originated by the erosion of
ancient cliffs and mountains.
Hutton’s conclusions led him to formulate a principle now known as
uniformitarianism. The principle states that geologic change occurs
over long periods of time, by a sequence of almost imperceptible
events. Hutton surmised that geologic processes operating today
also operated in the past. Thus, scientists can explain events that
occurred in the past by observing changes occurring today. Sometimes
this idea is summarized in the statement “The present is the key to
the past.”
Prof.Dr.Kadir Dirik Lecture Notes
Prof.Dr.Kadir Dirik Lecture Notes
William Whewell, another early geologist, agreed that the Earth is very old, but he
argued that geologic change was sometimes rapid. He wrote that the geologic past may
have “consisted of epochs of paroxysmal and catastrophic action, interposed between
periods of comparative tranquility.” Whewell was unable to give examples of such
catastrophes. He argued that they happen so infrequently that none had occurred
within human history.
Today, we know that both Hutton’s uniformitarianism and Whewell’s catastrophism are
correct. Thus, over the great expanses of geologic time, slow, uniform processes are
significant, but improbable, catastrophic events radically modify the path of slow
change.
Gradual Change in Earth History
Within the past few decades, geologists have learned that continents creep across the
Earth’s surface at a rate of a few centimeters every year.
Catastrophic Change in Earth History
Chances are small that the river flowing through your city will flood this spring, but if
you lived to be 100 years old, you would probably see a catastrophic flood. When we
study the 4.6 billion years of Earth history, they find abundant evidence of catastrophic
events that are highly improbable in a human lifetime or even in human history. For
example, giant meteorites have smashed into our planet, vaporizing enormous volumes
of rock and spreading dense dust clouds over the sky. Similarly, huge volcanic eruptions
have changed conditions for life across the globe. Geologists have suggested that these
catastrophic events have driven millions
ofDirik
species
into extinction.
Prof.Dr.Kadir
Lecture Notes
Prof.Dr.Kadir Dirik Lecture Notes
THE GEOLOGIC TIME
SCALE
Geologists have divided
Earth history into units
displayed in the geologic
time scale. The units are
called eons, eras, periods,
and epochs and are
identified primarily by the
types of life that existed at
the various times.
Prof.Dr.Kadir Dirik Lecture Notes
The Origin of the Solar System and the Differentiation of the Early Earth
The currently accepted theory for the origin of our solar system involves:
(a) a huge nebula condensing under its own gravitational attraction, then
(b) contracting, rotating, and (c) flattening into a disk, with the Sun forming in
the center and eddies gathering up material to form planets. As the sun
contracted and began to visibly shine, (d) intense solar radiation blew away
unaccreted gas and dust until finally, (e) the Sun began burning hydrogen and
Prof.Dr.Kadir Dirik Lecture Notes
the planets completed their formation.
Heat from the Sun boiled most of the hydrogen, helium, and other light
elements away from the inner Solar System. As a result, the four planets
closest to the Sun—Mercury, Venus, Earth, and Mars—are now mainly rocky
with metallic centers. These four are called the terrestrial planets because
they are “Earthlike.” In contrast, the four outer planets—Jupiter, Saturn,
Uranus, and Neptune—are called the Jovian planets and are composed
primarily of liquids and gases with small rocky and metallic cores.
(a) Mercury is a small planet close to the Sun. Consequently, most of the lighter
elements have long since been boiled off into space, and today the surface is solid and
rocky. (b) Jupiter, on the other hand, is composed mainly of gases and liquids, with a
Prof.Dr.Kadir Dirik Lecture Notes
small solid core.
(a)The early Earth was probably of uniform
Composition and density throughout,
(b) Heating of the early Earth reached the
melting point of iron and nickel, which,
being denser than silicate minerals, settled
to the Earh’s center. At the same time, the
lighter silicates flowed upward to form the
mantle and the crust.
(c) In this way, a differentiated Earth
formed, consisting of a dense iron-nickel
core, an iron-rich silicate mantle, and a
silicate crust with continents and ocean
basin
Prof.Dr.Kadir Dirik Lecture Notes
A schematic view of the
interior of the Earth
Jumps in density between Earth’s major layers caused by changes in their chemical
Prof.Dr.Kadir Dirik Lecture Notes
composition
Continents float high because they are made of rocks with lower densities than
rocks of the mantle or oceanic crust
Prof.Dr.Kadir Dirik Lecture Notes
Prof.Dr.Kadir Dirik Lecture Notes
Axial ridge
Divergent boundary
Transform
Subduction zone
Convergent boundary
Extensional zone in the continents
Prof.Dr.Kadir Dirik Lecture Notes
Uncertain plate boundary
Convection carries heat upward by the motion of matter
Mid-oceanic ridge
Trench
Ocean
Subduction
Continental
lithosphere
(Monroe&Wicander, 2005)
Prof.Dr.Kadir Dirik Lecture Notes
Oceanic
lithosphere
17
Mid-oceanic ridge
Transform
plate boundary
Upwelling
Divergent
plate boundary
ContinentalContinental
convergent
plate boundary
ContinentalOceanic
convergent
plate boundary
Asthenosphere
Lithosphere
Upwelling
Trench
OceanicOceanic
Divergent
plate boundary convergent
plate
boundary
(Monroe&Wicander, 2005)
An idealized cross section illustrating the relationship between lithosphere and
underlying asthenosphere and the three principal types of boundaries convergent
18
(yaklaşan), divergent (uzaklaşan) and transform (transform).
Prof.Dr.Kadir Dirik Lecture Notes
Prof.Dr.Kadir Dirik Lecture Notes
Prof.Dr.Kadir Dirik Lecture Notes
Prof.Dr.Kadir Dirik Lecture Notes
Prof.Dr.Kadir Dirik Lecture Notes