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GEOLOGY FOR MINING ENGINEERS
Prof.Dr.Kadir DİRİK
Lecture Notes
2015
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.
The hydrosphere includes water in streams, wetlands, lakes, and oceans; in the atmosphere; and frozen in glaciers. It also includes ground water present in soil and rock to a depth of at least 2 kilometers.
The atmosphere is a mixture of gases, mostly nitrogen and oxygen. It is held
to the Earth by gravity and thins rapidly with altitude. Ninety‐nine percent is
concentrated within 30 kilometers of the Earth’s surface, but a few traces
remain even 10,000 kilometers above the surface.
The biosphere is the thin zone near the Earth’s surface that is inhabited by
life. It includes the uppermost solid Earth, the hydrosphere, and the lower
parts of the atmosphere. Land plants grow on the Earth’s surface, with roots
penetrating at most a few meters into soil.
Animals live on the surface, fly a kilometer or two above it, or burrow a few
meters underground. Sea life also concentrates near the ocean surface,
where sunlight is available. Some aquatic communities live on the deep sea
floor, bacteria live in rock to depths of a few kilometers, and a few
windblown micro organisms are found at heights of 10 kilometers or more.
But even at these extremes, the biosphere is a very thin layer at the Earth’s
surface.
Prof.Dr.Kadir Dirik Lecture Notes
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 Lecture
speciesNotes
into extinction.
Prof.Dr.Kadir
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 the planets completed their formation. Prof.Dr.Kadir Dirik Lecture Notes
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 small
solid core.
Prof.Dr.Kadir Dirik Lecture Notes
(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
Givergent 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
Ocean
Trench
Subduction
Oceanic
lithosphere
Continental
lithosphere
(Monroe&Wicander, 2005)
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Prof.Dr.Kadir Dirik Lecture Notes
Mid‐oceanic ridge
Transform
plate boundary
Upwelling
Divergent
plate boundary
Continental‐
Continental
convergent
plate boundary
Continental‐
Oceanic
convergent
plate boundary
Trench
Oceanic‐
Oceanic
Divergent
plate boundary convergent
plate
boundary
Asthenosphere
Upwelling
(Monroe&Wicander, 2005)
Lithosphere
An idealized cross section illustrating the relationship between lithosphere and underlying
asthenosphere and the three principal types of boundaries convergent (yaklaşan), divergent
(uzaklaşan) and transform (transform).
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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