Department of Mining Engineering,
Faculty of Engineering,
Unity University
GENERAL GEOLOGY
GEOL 2081
By
Tadesse Alemu
Director
Basic Geoscience Mapping Directorate
Geological Survey of Ethiopia
tadessealemu@yahoo.com
0912-175773
October 2012
Addis Ababa
CLIMATE SETTING
• Introducing each other
• Why you choose to study Mining Engineering?
• Your expectation from the course
• Set norms
2
objectives
 To acquaint the students with the basic knowledge of geology, this
is applicable in the field of Mining Engineering.
3
Outcomes
At the end of the course the students shall be able to:
•Identify, classify, and describe Minerals and Rocks based on
physical properties and textures.
•Recognize and evaluate geologic structures.
•Discuss geologic time, basic stratigraphic principles, and
explain clearly the major geological time divisions that have
been important in the formation of the earth .
•Interpret geologic environments based on rock type.
•Explain the geological evolution of Ethiopia
4
CONTENTS
Scope in Mining Engineering.
Introduction to various branches of geology.
Origin of the earth and its place in universe, interior of the earth and
chemical composition of the earth’s crust.
Mountain building and valley formation, drainage patterns and their
types, agents of weathering and erosion.
Deformational structural features of rocks, dip, strike, faults, folds,
joints and fissures, unconformities etc.
Introduction to continued drift and plate tectonics, earth quakes and
volcanism with special reference to Ethiopia.
Formation of rocks and minerals, classification of rocks.
Occurrence of economic minerals and dimension stones of Ethiopia.
5
Lab Exercises
1. Identification of rock forming minerals and rocks
2. Mohs’ Scale Hardness
3. Study of wooden models of faults and folds etc.
4. Measurement of dip and strike
5. Geological map reading
6.International geological symbols for rocks, structures and mineral
Teaching & Learning Methods
– Lectures, , exercise, project work
• Assessment/Evaluation & Grading System
continuous assessment (assignments) 50%
written and practical tests (final examination) 50%
• Attendance Requirements
Students are expected to attend at least 80% of the course
Literature
1. K. M. Banger, Text book of Geology
2. H. H. Read, Rutley’s Mineralogy
3. Dana, Dana’s Manual of Mineralogy
4. Santosh Kumar Grag, Text book of Geology
5. Raymond, L. A., The Study of Igneous, Sedimentary and
Metamorphic Rocks, McGraw Hill, 2002
6. Arthur Holmes and Dorris Holmes, Physical Geology F. G. H. Blyth, Geology for
Engineers
INTRODUCTION
Mining Engineering
• Is an engineering discipline that involves the practice, the
theory, the science, the technology, and application of
extracting and processing minerals from a naturally
occurring environment.
• Also includes processing minerals for additional value.
•Mining engineers are involved in the mineral discovery stage by
working with geologists to identify a mineral reserve.
•The first step in discovering an ore body is to determine what
minerals to test for.
•Geologists and engineers drill core samples and conduct surface
surveys searching for specific compounds and ores. For example, a
mining engineer and geologist may target metallic ores such as galena
for lead or chalcopyrite for copper. A mining engineer may also search
for a non-metal such as phosphate, quartz, or coal.
• The function of the Mining Engineer is to apply knowledge of pertinent
scientific theory, engineering fundamentals, and improved technology to
recover natural resources.
•Mining is a world-wide activity involving the extraction of nonmetallic,
metal ores of all kinds, and solid fuels and energy sources such as coal and
nuclear material.
•In addition to mineral extraction, the skills of Mining Engineers are also
needed in a variety of fields where the earth's crust is utilized.
• The construction industry, with its requirements of developing roads,
railroads, tunnels, and underground chambers, and the hazardous waste
disposal industry are examples of such applications.
• These are rapidly expanding needs, with a shortage of competent people;
the mining engineer is well qualified to meet these needs.
• The importance of ecological and environmental planning is recognized
and given significant attention in all aspects of the mining engineering
curriculum.
GEOLOGY
What is it?
• Geology is the study of the Earth.
• It includes not only the surface process which have shaped the
earth's surface, but the study of the ocean floors, and the interior of
the Earth.
• It is not only the study of the Earth as we see it today, but the
history of the Earth as it has evolved to its present condition.
Branches of Geology
• Geology is divided into several fields, which can be grouped under the major
headings of Physical and Historical geology.
Physical geology includes:
mineralogy, the study of the chemical composition and structure of minerals;
petrology, the study of the composition and origin of rocks;
geomorphology, the study of the origin of landforms and their modification by
dynamic processes;
geochemistry, the study of the chemical composition of earth materials and the
chemical changes that occur within the earth and on its surface;
geophysics, the study of the behavior of rock materials in response to stresses and
according to the principles of physics;
sedimentology, the science of the erosion and deposition of rock particles by wind,
water, or ice;
structural geology, the study of the forces that deform the earth's rocks and the
description and mapping of deformed rock bodies;
economic geology, the study of the exploration and recovery of natural resources,
such as ores and petroleum; and
engineering geology, the study of the interactions of the earth's crust with humanmade structures such as tunnels, mines, dams, bridges, and building
foundations.
Historical geology deals with the historical development
of the earth from the study of its rocks.
They are analyzed to determine their structure,
composition, and interrelationships and are examined for
remains of past life.
Historical geology includes:
 paleontology, the systematic study of past life forms;
stratigraphy, of layered rocks and their interrelationships;
 paleogeography, of the locations of ancient land masses
and their boundaries; and
geologic mapping, the superimposing of geologic
information upon existing topographic maps
Early History of the Earth
Early History
•
•
•
The earth and the rest of the solar system were formed about 4.57 billion years ago from
an enormous cloud of fragments of both icy and rocky material which was produced from
the explosions (super novae) of one or more large stars.
It is likely that the proportions of elements in this material were generally similar to those
shown in the diagram below.
Although most of the cloud was made of hydrogen and helium, the material that
accumulated to form the earth also included a significant amount of the heavier
elements, especially elements like carbon, oxygen, iron, aluminum, magnesium and
silicon.
• As the cloud started to contract, most of the mass accumulated
towards the centre to become the sun. Once a critical mass
had been reached the sun started to heat up through nuclear
fusion of hydrogen into helium.
• In the region relatively close to the sun - within the orbit of
what is now Mars - the heat was sufficient for most of the
lighter elements to evaporate, and these were driven outward
by the solar wind to the area of the orbits of Jupiter and the
other gaseous planets.
• As a result, the four inner planets - Mercury, Venus, Earth and
Mars are "rocky" in their composition, while the four major
outer planets, Jupiter, Saturn, Neptune and Uranus are
"gaseous".
Gas
Venus
Carbon dioxide
Nitrogen
Oxygen
Methane
Average T (°C)
Pressure (bars)
Earth without life
96.5%
98%
3.5% 1.9%
trace
0
0
0
459 290
90
60
Mars
95%
2.7%
0
0
-53
.00064
Earth with life
0.03%
79%
21%
1.7 ppm
13
1.00
Geologic Time Scale
Geologists have divided up time into two
eons, namely: Proterozoic, and Phanerozoic.
 Most of the rocks exposed at surface are of
Phanerozoic age. There are exposed rocks of
Proterozoic and Archean age
Some Geologists have divided up time into
four eons, namely: Hadean (Pre-Archean),
Archean, Proterozoic, and Phanerozoic .
Up until recently the oldest known rock in the
world - ~ 4.0 billion years (b.y.) old – was the
Acasta Gneiss, situated at the eastern edge of
Great Slave Lake. In 2008 some even older rocks
were discovered at a place called Nuvvuaglittuq on
the eastern shore of Hudson Bay. These rocks are
estimated to be ~4.28 b.y. old making them
Hadean in age. (O’Neill et al., 2008, Science, V. 321,
p. 1828.)
Important point:
•The Earth has evolved (changed) throughout its
history, and will continue to evolve.
•The Earth is about 4.6 billion years old, human
beings have been around for only the past 2 million
years. Thus, mankind has been witness to only
0.043% of Earth history.
•The first multi-celled organisms appeared about 700
million years ago. Thus, organisms have only been
witness to about 15% of Earth's history.
Why Study the Earth?
 We're part of it.
 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 / cyclones,
landslides, could affect us at any time. A better understanding of the Earth is
necessary to prepare for these eventualities.
Earth Materials and Processes
The materials that make up the Earth are mainly rocks (including soil, sand, silt,
dust). Rocks in turn are composed of minerals. Minerals are composed of
atoms,
Processes range from those that occur rapidly to those that occur slowly
Examples of slow processes
• Formation of rocks
• Chemical breakdown of rock to form soil (weathering)
• Chemical cementation of sand grains together to form rock (diagenesis)
• Recrystallization to rock to form a different rock (metamorphism)
• Construction of mountain ranges (tectonism)
• Erosion of mountain ranges
Examples of faster processes
• Beach erosion during a storm.
• Construction of a volcanic cone
• Landslides (avalanches)
• Dust Storms
• mudflows
Processes such as these are constantly acting upon and within the Earth to change it. Many
of these processes are cyclical in nature.
Most surface rocks started out as igneous rocks- rocks produced by crystallization from a
liquid. When igneous rocks are exposed at the surface they are subject to weathering
(chemical and mechanical processes that reduce rocks to particles). Erosion moves particles
into rivers and oceans where they are deposited to become sedimentary rocks. Sedimentary
rocks can be buried or pushed to deeper levels in the Earth, where changes in pressure and
temperature cause them to become metamorphic rocks. At high temperatures metamorphic
rocks may melt to become magmas. Magmas rise to the surface, crystallize to become
igneous rocks and the processes starts over.
THE SOLID EARTH
The Solid Earth
• The Earth has a radius of about 6371 km, although it is
about 22 km larger at equator than at poles.
Internal Structure of the Earth
• The internal structure of the earth Although we can't see into the earth, and
the deepest drill-hole is only 13 km, we have a reasonably good picture of its
internal structure and composition.
• Firstly, we can observe material which has been pushed up to surface from
great depth - including parts of the ocean floor, and kimberlitic material from
deep within the mantle3, the rocks in which diamonds are found.
• Secondly, we can observe meteorites, most of which are thought to be parts
of broken up planets or planetesimals (little planets).
• Most importantly, however, we can study and understand seismic waves.
Seismic waves are physical disturbances in a body of rock - caused by
earthquakes or artificial explosions - which travel through the rock like a
wave across a body of water. They are divided into two types:
– P (Primary, compressional or push) waves - like a coil spring (or slinky)
– S (Secondary or shear) waves - like a piece of rope which has been flicked
A kimberlite is a volcanic eruption with a source deep within the mantle (as opposed to the upper part of the crust for
typical volcanoes). Kimberlitic magma travels quickly to the earth's surface and, in some cases, passes through a zone in
which diamonds are stable. If some of these diamonds are incorporated into the kimberlite, and if they survive the
journey to the surface, a diamond-bearing deposit may form.
Surface Features of the Earth
• Oceans cover 71 % of Earth's surface -- average depth 3.7
km.
• Land covers remaining surface with average of 0.8 km above
sea level.
Ocean Basins
•Continental Shelf, Slope, and rise
•Abyssal Plains
•Oceanic ridges
Oceanic Trenches
Earth Plates
Plate Boundaries
Divergent Boundaries
Convergent Boundaries
occur at Oceanic Ridges, where new Oceanic occur where oceanic lithosphere is
lithosphere is formed and moves away from pushed back into the mantle, marked by
the ridge in opposite directions
oceanic trenches and subduction zones.
Transform Boundaries
occur where two plates slide past one another
horizontally. The San Andreas Fault, in
California is a transform fault.