By Tadesse Alemu

1. 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

2. CLIMATE SETTING • Introducing each other • Why you choose to study Mining Engineering? • Your expectation from the course • Set norms

3. objectives • To acquaint the students with the basic knowledge of geology, this is applicable in the field of Mining Engineering.

4. Outcomes • 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 At the end of the course the students shall be able to:

5. 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.

6. 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

7. 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

8. INTRODUCTION

9. 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.

10. 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.

11. 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.

12. 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 human-made structures such as tunnels, mines, dams, bridges, and building foundations.

13. 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

14. 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.

15. 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".

16. Gas Venus Earth without life Mars Earth with life Carbon dioxide 96.5% 98% 95% 0.03% Nitrogen 3.5% 1.9% 2.7% 79% Oxygen trace 0 021% Methane 0 001.7 ppm Average T (°C) 459 290 -53 13 Pressure (bars) 90 60 .00064 1.00

18. 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.)

19. 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.

20. 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.

21. 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.

22. 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.

23. THE SOLID EARTH

24. The Solid Earth • The Earth has a radius of about 6371 km, although it is about 22 km larger at equator than at poles.

25. Internal Structure of the Earth

26. 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.

28. 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

29. Earth Plates

30. Plate Boundaries Convergent Boundaries occur where oceanic lithosphere is pushed back into the mantle, marked by oceanic trenches and subduction zones. Divergent Boundaries occur at Oceanic Ridges, where new Oceanic lithosphere is formed and moves away from the ridge in opposite directions Transform Boundaries occur where two plates slide past one another horizontally. The San Andreas Fault, in California is a transform fault.