Geology for Engineers PDF

GEOLOGY FOR ENGINEERS Magneto stratigraphy – how sedimentary and INTRODUCTION volcanic sequences are dated by geo-physically GEOLOGY correlating samples of s...

GEOLOGY FOR ENGINEERS Magneto stratigraphy – how sedimentary and INTRODUCTION volcanic sequences are dated by geo-physically GEOLOGY correlating samples of strata deposited with Earth’s - ‘Geoscience’ or ‘Earth Science’. magnetic polarity. - Study of the structure, evolution, and dynamics of Geochronology – how old rocks and geological the Earth and its natural resources. events are dated using signatures inherent rocks. - Investigates the process that have shaped the TECTONICS understands moving plates Earth through its 4500 million (approximate) year - Seismology, volcanoes, earthquakes… branches history and uses the rock record to unravel that have a common theme: Underlying process history. that impacts them are Plate Tectonics. - Concerned with the real world beyond the - Seismology, measure how waves travel through laboratory and has direct relevance to the needs and around Earth form earthquakes and of society. Tectonophysics, physical processes that acts on the BRANCHES OF GEOLOGY behavior of waves. Geology – physical features and the processes that - Plays a key role in volcanoes, volcanology explains act on their development. how and where volcanoes and related phenomena Chronology – layers of rock as it relates to geologic (lava and magma) erupt and form (past and time. present. Tectonics – applying the principles of plate tectonics Tectonics – how Earth’s crust evolves through time to geology. contributing to mountain building, old core Natural Resources – examining rocks, terrain, and continents (cratons) and earthquakes/volcanoes. materials as natural resources. Volcanology – how volcanoes erupt, anatomy of a Sedimentology – erosion, movement, and volcano, and related phenomena (lava, magma) deposition of sediments. erupt and form (past, present). Topography – mapping terrain and processes that Seismology – how seismic waves travel through and act on it. around the Earth from earthquakes. Astrogeology – classifying rocks and land forms Neotectonics – how Earth’s crust deforms and has outside Earth. moved in recent and current time. Branches that focus on TIME Tectonophysics – how Earth’s crust and mantle - Deals with time and concerned with deforms specific to it physical processes. reconstructing the past. Whether it’s fossils, Seismotectonic – how earthquakes, active tectonics magnetic fields, or types of landforms. and individual faults are related to seismic activity. - “Paleo” common in this field. Paleo is short for Branches focused on NATURAL RESOURCES “paleolithic” which refers to the geologic past. - Most geology careers involve the extraction of Stratigraphy – how layering of rocks and strata are natural resources from the surface. This where analyzed to measure geologic time. geologist relate rock types and landforms in a - layering of archeological remains and specific environment. their position on layers of rock - EX: Petrology uses mineralogy and rock types to - EX: Magneto stratigraphy, studies understand geological formations from drilling, magnetic fields in rocks and past pole they also study chemical properties and how reversals. atoms are arranged. Paleontology – how organisms evolved and their - Soils are also considered a natural resource for interactions in their environment by studying fossil agriculture production. Agronomy, edaphology, records often found in rocks. and pomology are specific to soil science and how Micropaleontology – how microfossils are food grows or is cultivated. characterized. Petrology – how types of rocks (igneous, Paleomagnetism – how to reconstruct previous metamorphic, and sedimentary) form in their magnetic fields in rocks including direction and specific environment. intensity to explore pole reversals in different time Mineralogy – how chemical and crystalline periods. structures in minerals are composed. Geomorphology – how landforms, physical features, Gemology – how natural and artificial gems are and geological structures on Earth were created and identified and evaluated. evolved. Crystallography – how atoms are arranged and Paleoseismology – how geologic sediments and bonded in crystalline solids. rocks are used to infer past earthquakes.  Soil Sciences – how soils relate as a natural resource EARTH STRUCTURE AND COMPOSITION including their formation factors, classification, physical, chemical, and fertility properties. Pedology – how soils are classified based on their biological, physical, and chemical properties. Edaphology – how soils influence plant growth and living things. Agronomy/Agrology - how the field of science such as crop production, biotechnology, and soil science. Hydrogeology – how groundwater is transported and is distributed in the soil, rock, and Earth’s crust. Pomology – how fruits grow and are cultivated. TOPOFRAPHY studies land forms and their processes - Examines the physical features that are distributed on the landscape. - EX: Orography focuses on topographic relief and EARTHQUAKES how mountains are distributed. Without tectonic - Is what happens when two blocks of the Earth plates, mountain building is not possible. suddenly slip past one another. - EX: Hypsometry measures the height and depth of - Fault or Fault Plane, the surface where they slip. physical features from the mean sea level. Used to - Hypocenter, the location below the Earth’s surface understand the profile of Earth and landscape where the earthquake starts. evolution. - Epicenter, the location directly above it on the Orography – how topographic relief in mountains surface of the earth. are distributed in nature. - Sometimes earthquake has Foreshocks. These are Topography – how physical features (natural and smaller earthquakes that happen in the same artificial) are arranged on the landscape. place as the larger earthquakes that follows. Hypsometry – how height and depth of physical Scientists can not tell that an earthquake is a features are measured land from mean sea level. foreshock until the larger earthquake happens. ASTROGEOLOGY involves geology outside Earth - The largest, main earthquake is called the - Mars Rover started wheeling around the red Mainshock. planet, its crosshairs were targeting the rocks and - Mainshocks always have Aftershocks that follows. geology of Mars (close-up and personal of the These are smaller earthquakes that occur composition of Mars). afterwards in the same place as the mainshock. - Closely related to exogeology. Both focus on how - Depending on the mainshock, aftershocks can geology relates to celestial bodies such as moons, continue for weeks, months, and even years after asteroids, meteorites, and comets. the main. - EX: Selenography, studies physical features of What causes Earthquakes and Where do they happen? moon. It understands and catalog features such as - The earth has four major layers: Inner Core, Outer lunar maria, craters, and mountain ranges on the Core, Mantle, and Crust. moon. - Crust and Top of the Mantle make up the thin skin Astrogeology – how geology relates to celestial on the surface of our planet or Lithosphere. bodies like moon, asteroids, meteorites, and - This thin skin is not all in one piece – it is made up comets. of many pieces like puzzle covering the surface of Areology – how geology is composed on Mars. the earth. This puzzle pieces keep slowly moving Selenography – how physical features on the moon around, sliding past one another, and bumping formed such as lunar maria, craters, and mountain into each other. We call these puzzle pieces ranges. Tectonics Plates, and the edges of the plates are Exogeology – how geology relates to celestial bodies called Plate Boundaries. like moons, asteroids, meteorites, and comets. - Plate boundaries are made up of many faults, and most earthquakes around the world occur on these faults. Since the edges are rough, they get stuck while the rest of the plate keeps moving. Finally, when the plate has moved far enough, the edges unstick on one if the faults and there is an earthquake.  EARTH’S STRUCTURE AND COMPOSITION Earth - A planetary body and important member of the solar system. - Third terrestrial planet characterized with well- defined atmosphere made up chiefly of Nitrogen and Oxygen and having a mean density of 5.5 g/cm3, which is the highest in the entire solar system. - Only planet that can sustain life. - The mas age of the earth as determine from Why does the earth shake when there is an radioactive dating is put at 4.543 billion years earthquake? (approx. 4.6 billion years). - While the edges are stuck, the rest moves, the Parts of Earth – as a planet energy that would normally cause the blocks to - It is commonly described as spheroid. slide past one another is being stored up. - It is commonly differentiated into three parts: - When the force of the moving blocks finally Atmosphere, Lithosphere, and Hydrosphere. overcomes the friction of the jagged edges of the Atmosphere fault and it unsticks, all the stored-up energy is - outer gaseous part. released. - starts at the surface and extends up to 700 km and - The energy radiates outward from the fault in all even beyond. directions in the form of seismic waves like ripples - makes about one-millionth part of the total mass in the pond. The seismic waves shake the earth as of earth. they move through it, and when the waves reach - is held around the planet due to gravitational pull the earth’s surface, they shake the ground and of the body of earth. anything on it. - layers (descending order): How are earthquakes recorded? o Exosphere - They are recorded by instruments called o Thermosphere Seismographs. The recording they make is called o Mesosphere Seismogram. o Stratosphere - Seismographs has a base that sets firmly in the o Ozone Layer ground, and a heavy weight that hangs free. When o Troposphere the earthquake occurs, the base shakes but the Lithosphere hanging weight does not. Instead, the spring or - stony part of the Earth (litho = stone). string that is hanging from absorbs all the - includes all solid materials composing earth from movement. The difference in position between the the surface downwards. shaking part of it and the motionless part is what - layer (descending order): is recorded. o Crust How does the scientists measure the size of o Mantle earthquakes? o Core - The size depends on the size of the fault and the - consists of the core and upper mantle, up to which amount of slip on the fault. the material exists in definite solid state. - They use seismogram recordings to determine Hydrosphere how large the earthquake was. Short wiggle - collective name for all the natural water bodies means small earthquake and a long wiggly one occurring on or below the surface of Earth. mean large earthquake. - basically, means the water on Earth. - The length of wiggles depends on the size of fault - 0.03% of Earth’s mass. while the size of the wiggle depends on the - its relevance to existence of life on this planet can amount of slip. hardly be overstated. - The size of earthquake is called Magnitude. There is one magnitude for each earthquake. Intensity of an earthquake varies depending on where you are during the earthquake. Statistics about Earth: The Continental Crust – is further distinguished Shape Oblate Spheroid into three layers: A, B and C. has a thickness of around 30 km from the upper mantle Equatorial Radius 6378 km Polar Radius 6357 km - The A or the Upper Layer is between 2-10 km thick and is of low density (2.2 g/cm3). It is sometimes called Mean Radius 6371 km Sedimentary Layer because it is mostly made up of Surface Area 1.101 x 1014 m2 Sedimentary rocks. Water Cover 70.8% - The B or the Middle Layer of the continental crust has Land Cover 29.2% a thickness of 20 km or more and is relatively dense (2.4 Mount Everest – 2.6 g/cm3). It is sometimes called the Granite Layer Highest Point because it mostly consists of granites, gneisses and 8848 m other related igneous or metamorphic rocks. Average Elevation 840 m Challenger Deep - The C layer is the lowermost layer of the continental Greatest Depth (Marianas Trench) crust with a thickness of around 25 – 40 km under the 11030 m continents with a density of around 2.8 to 3.3 g/cm3. Average Depth 3800 m This layer is also referred as Basaltic Layer of the crust. It is made predominantly of basic minerals (rich in Volume 1.083 x 1021 m3 magnesium silicates) and hence is sometimes named as Mass 5.977 x 1024 kg SIMA (Si for silica and Ma for Magnesium). The Oceanic Crust – it is generally the extension Intro to Structure of Earth of C layer of the continental crust. The oceanic - The real interior of the Earth is nowhere exposed crust has a thickness of 5 – 7 km from the upper to our direct observation. With our present mantle and has a density of 3.00 g/cm3. scientific skills, we can hardly penetrate up to kilometers below the surface of the Earth whereas How are Mountains Formed? the average radius of the Earth is 6,371 km. - due to collision of continental plates, lifting any - Therefore, the entire discussion given below side or both sides up leading to the formation of about the internal structure of the Earth is based Mountain Ranges. on the evidence yielded by indirect geophysical 2. Mantle - the second concentric shell of the Earth methods. The study of seismic waves (released that lies beneath the crust everywhere and consists during earthquakes and nuclear shocks) forms the of molten rocks. This zone starting from the lower single most important source of information of the boundary of the crust (top of the upper mantle to interior of the Earth. bottom of lower mantle) continues up to a depth of - The parts of the Earth can be categorized in to 2,900 km and is made up of silicates. two, based on chemical composition. And based - The exact nature of the mantle is as yet on physical/mechanical properties. Under incompletely understood. It has been sub-divided chemical properties, there are three; Crust, in to an upper and lowers mantle, the boundary Mantle and Core. And in physical/mechanical between the two layers being placed at 900 – properties, there are five; Lithosphere, 1000 km below the earth. The mantle is Asthenosphere, Mesosphere, Outer Core, Inner responsible for all the Earth’s volcanic and seismic Core. activities. Parts of the Earth based on Chemical Properties: - In here, the temperature of the rock is of melting point. When heat is present, pressure is present 1. Crust – it is the uppermost shell of the Earth that and when pressure is present, there will be extends to variable depths below the mountains (75 movement of tectonic plates. km), continents (35 km) and oceans (5 km). The crust in general has a thickness of 0 km to 100 km Parts of Mantle: and mostly made up of silicates and it is also where a. Upper Mantle - The upper mantle begins at a you can find the three types of rocks, igneous, depth of 5 to 50 km and extends to a depth of sedimentary and metamorphic. There are two approximately 670 km from the surface with a types of crust, namely the continental crust and density of 3.4 g/cm3. oceanic crust.  b. Lower Mantle - The lower mantle begins at a depth of 720 to 2900 km with a density of 4.4 g/cm3. 3. Core - the innermost concentric shell of the Earth. Also referred to as the NiFe layer (Ni – nickel, Fe – Iron) because it is mostly composed of nickel and iron. The core boundary begins at a depth of 2900 km from the surface and it extends to the center of the Earth at 6,371 km. it has an approximate thickness of 3,500 km. a. Outer core - mostly made up to Ni + Fe at a temperature ranging from 4,000°C – 5,000°C. the outer core is in liquid state with a thickness of 2,300 km. b. Inner core – mostly made up to Fe at a temperature of 5,000°C – 7,000°C. the inner core is in solid state with a thickness of 1,200 km. Parts of the Earth based in Physical/Mechanical Properties: 1. Lithosphere - This rigid layer of solid rock "floats" on top of the asthenosphere. It is the combination of the crust and the upper mantle, its thickness ranges from 0 – 100 km with a density of around 2.7 g/cm3. 2. Asthenosphere - this layer has a consistency of a soft plastic meaning it flows and at the same time elastic, it mostly comprises of the upper mantle only, its thickness ranges from 100 – 350 km with a density of around 3.3 g/cm3. Tectonic plates are located above the asthenosphere. 3. Mesosphere – this layer is made of a stiff plastic (very hot solid rock), it mostly comprises of the lower mantle, its thickness ranges from 350 – 2900 km with a density of around 4.5 g/cm3. 4. Outer core – the consistency of this core is in liquid state with a thickness ranging from 2900 – 5200 km and a density of 9.9 - 12.2 g/cm3. 5. Inner core – the consistency of this core is in solid state with a thickness ranging from 5200 – 6371 km and a density of 12.8 – 13.1 g/cm3.