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Applied Geology
GENERAL GEOLOGY 1. Geology in Civil Engineering 2. Branches of geology 3. Earth Structures and composition 4. Continental drift & plate technologies 5. Earth processes 6. Earthquake belts in India
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7. Groundwater
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8. Importance in civil engineering
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DEFINITION
The study of
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Earth
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GEOLOGY
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Geology = The study of Earth
OUTER CORE
- HOT!!!! – Thought to be as hot as the surface of the Sun! - Solid - Composed of Iron and Nickel
HOT! (but not as hot as the inner core) Liquid Composed of Iron and Nickel
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INNER CORE
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CRUST
Still hot! – but not as hot as the core! Largest layer Composed of various materials Solid and liquid
Cool What we live on Composed of rocks, various materials make up the crust Solid or Liquid?
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MANTLE
- The Earth’s crust is divided into segments called plates.
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Even though 70% of the Earth’s surface is water, there is crust under the water. The water sits on top of the crust!
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-The Earth’s crust moves!!!!! -The continents have not always been arranged like they are today.
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Pangaea
Supercontinent that existed 250 million years ago All the land made up 1 continent until its split into the modern day configuration of the continents. Discovered by Alfred Wegner in 1912, but not accepted by the public until after his death in the 1950’s.
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BRANCHES OF GEOLOGY Physical Geology It deals with the origin, development and ultimate fate of various surface features of the earth and also with its internal structure. • The role played by internal agents and external agent on the physical features of the earth makes major areas of study in physical geology.
It enables a civil engineer to understand engineering applications of certain conditions related to the area of construction, which are essentially geological in nature.
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It enables a geologist to understand the nature of geological information that is absolutely essential for a safe design and construction of a civil engineering project.
Mineralogy
Geomorphology
Mineralogy formation, minerals.
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Minerals occurring in natural aggregated form are called rocks; these rocks form the building blocks that make up the crust of the earth.
Historical Geology It deals with the past history of the. Rocks may be treated as pages of the Earth’s history. They contain within them enough evidence indicative of nature and time of their formation, composition, constitution, magnetism, structural disposition and in many cases, fossils (remains of ancient life), all of which when interpreted scientifically reveal a lot about the events that have passed since their formation.
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The structure and evolution of these landforms through space and time are advanced fields of study within geomorphology.
is that branch of geology, which, deals with occurrence, aggregation, properties, and uses of
Petrology
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Detailed investigations regarding development and disposition of mountains, plains, plateaus, valleys and basins and various other landforms associated with them; fall in the domain of geomorphology.
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Deals specifically with the study of surface features of the earth, primarily of the land surface.
Economic Geology
The branch deals with the study of those minerals and rocks and other materials (fuels etc) occurring on and in the earth that can be exploited for the benefit of man. These include a wide variety of ores of all the metals and non-metals, building stones, salt deposits, fuels (coal, petroleum, natural gas and atomic minerals) and industrial minerals refractories, abrasives and insulations and for manufacture of chemicals.
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EARTH STRUCTURES AND COMPOSITION
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Atmosphere
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The outer gaseous part of the Earth starting from the surface and extending as far as 700 km and even beyond is termed atmosphere. It makes only about one-millionth part of the total mass of the Earth. The gaseous envelope, like the other matter, is held around the planet due to gravitational pull of the body of the Earth.
Stratosphere
Troposphere
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It is the second layer of the atmosphere starting from the tropopause and extending up to an average height of 50 km
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Temperature becomes constant for a height of 20km (above tropopause) and then starts increasing. contains almost the entire concentration of OZONE GAS that occurs above the Earth in the form of a well-defined envelope distinguished as the Ozone layer Ozone Layer starts at a height of 9 km above the surface and continues up to 35 km. The maximum concentration of ozone in this layer is estimated at a height of 20- 25km. The importance of ozone layer for the life on the planet Earth lies in its capacity to absorb a good proportion of the solar radiation including the entire content of most dangerous ultraviolet rays coming from the Sun.
In this process, the gas gets itself heated up and hence becomes the cause of higher temperature in the upper regions of the atmosphere. upper boundary of the stratosphere - stratopause.
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It is the lower most zone of the atmosphere rising from the surface of the earth extending, on an average to a height of 11 km. Its upper boundary called tropopause about 9km above the poles and at 18 km above the equator. The troposphere contains almost nine-tenths of the total mass of the atmosphere this layer of gases that is responsible for most of the weather forming or processes on the earth. In the troposphere there is recorded a regular fall in tem a lapse rate of 6.3 up to tropopause resulting to as low temperatures as —40 C to -60 degree at those heights.
IONOSPHERE
This is the third thermal zone of atmosphere which begins at stratopause at about 50km above the surface and continues up to a height of about 80 km. It is characterized with a steep fall in temperature that may go to as low levels as — 100 °C at the upper limit of mesosphere.
The fourth and the last zone of the atmosphere starts at about 80 km and extends up to 500 km and beyond. In this zone, temperature starts rising once again and reaches 1000°C and above. The IONOSPHERE is a special zone recognized within the atmosphere. It starts from 80 km and extends upwards to variable heights. Atmospheric gases at these heights absorb a great part of solar radiation coming to the Earth. In this process, these gases break up into ions or electrically charged particles. As a result, this part is made up of entirely ions and hence is designated as ionosphere.
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Mesosphere
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Lithosphere Crust Mantle Core
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Outer Core Inner Core
Crust
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When compared with the radius of the Earth (6730 km. on an average), the crust makes just an insignificant part in the structure of the earth Chemical Cmposition: Silica- >50% in oceanic Crust, >62% in continental Crust Alumina - 13-16 percent Iron Oxide - (Fe Lime (CaO)-6%; Sodium Oxide-4%, Magnesium Oxide-4%,Potassium Oxide and Titanium oxide- 2%
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The solid aggregate that makes the crust of the earth is named as a rock. The entire crust is made up of different types of rocks.
Materials making the earth become quite different in properties at the base of the crust. This depth below the surface of the Earth at which a striking change in the properties of the materials is observed has been named as Mohorovicic discontinuity ( Moho). The material below Moho forms a nearly homogeneous zone till a depth of 2900 km is reached. Mantle is made up of extremely basic material called aptly ultra basic, that is very rich in iron and magnesium but quite poor in silica The material of the mantle is believed to be variably viscous in nature so much so that the overlying crusted blocks can virtually float over it.
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Under the oceans 5 - 6 km Under the continents 30 - 35 km Under the mountains: 60 - 70 km
Mantle
Hydrosphere
It starts at a depth of 2900 km below the surface and extends right up to the center of the earth, at a depth of 6370 km. The physical nature and composition of the material is not uniform throughout its depth. It has a very high density at mantle-core boundary, above l0g/cc. ( water 1gm/cc) Outer core - 2900 km to about 4800 km Inner Core - 4800 km to 6370km.
It is a collective name for all the natural water bodies occurring on or below the surface. Although hydrosphere makes only 0.03 percent of mass of the earth as a planet, its relevance to the existence of life on this planet can hardly be overstated More than 98 percent of the hydrosphere is made up of huge surface bodies of saline water called seas and oceans. Rivers and lakes spread over hundreds of thousands square kilometers are other constituents of the hydrosphere.
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Core
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Biosphere
Plate tectonics
This term is sometimes used to express the collective life form, as it exists on the surface and under water.
Plate tectonics (from the Late Latin tectonicus, from the Greek: "pertaining to building") is a scientific theory that describes the large-scale motions of Earth's lithosphere. The lithosphere is broken up into tectonic plates. On Earth, there are seven or eight major plates (depending on how they are defined) and many minor plates. Where plates meet, their relative motion determines the type of boundary: convergent, divergent, or transform. Earthquakes, volcanic activity, mountain-building, and oceanic trench formation occur along these plate boundaries Tectonic plates are composed of oceanic lithosphere and thicker continental lithosphere, each topped by its own kind of crust
The biosphere depends for its existence on the other three zones of the planet already described: the lithosphere, the atmosphere and the hydrosphere.
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This zone has also been responsible for many geological processes that have been going on the planet since the evolution of life.
Types of plate boundaries
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Transform boundaries (Conservative): occur where plates slide or, perhaps more accurately, grind past each other along transform faults. Divergent boundaries (Constructive): occur where two plates slide apart from each other. Mid-ocean ridges (e.g., Mid-Atlantic Ridge) and active zones of rifting (such as Africa's East African Rift) are both examples of divergent boundaries. Convergent boundaries (Destructive) (or active margins): occur where two plates slide towards each other commonly forming either a subduction zone (if one plate moves underneath the other) or a continental collision (if the two plates contain continental crust).
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Plate Movements
Mr.T.Karthikeyan M.E (Geotech), AP/Civil, VSAGI Salem 10
Plate tectonics Plate tectonics (from the Late Latin tectonicus, from the Greek: "pertaining to building") is a scientific theory that describes the large-scale motions of Earth's lithosphere. The lithosphere is broken up into tectonic plates. On Earth, there are seven or eight major plates (depending on how they are defined) and many minor plates. Where plates meet, their relative motion determines the type of boundary: convergent, divergent, or transform. Earthquakes, volcanic activity, mountain-building, and oceanic trench formation occur along these plate boundaries Tectonic plates are composed of oceanic lithosphere and thicker continental lithosphere, each topped by its own kind of crust
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Types of Weathering Mechanical (physical) weathering is the physical disintegration and reduction in the size of the rocks without changing their chemical composition. Examples: exfoliation, frost wedging, salt wedging, temperature changes, and abrasion Chemical weathering decomposes, dissolves, alters, or weakens the rock through chemical processes to form residual materials. Examples: carbonation, hydration, hydrolosis, oxidation, and solution Biological weathering is the disintegration or decay of rocks and minerals caused by chemical or physical agents of organisms. Examples: organic activity from lichen and algae, rock disintegration by plant or root growth, burrowing and tunneling organisms, and acid secretion Table of Contents
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EARTH PROCESS
Mechanical Weathering: Exfoliation
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Natural process of in-situ disintegration of rocks into smaller fragments and particles through essentially physical processes without a change in their composition. A single rock block on a hill slope or a plain, for instance, may be disintegrated gradually into numerous small irregular fragments through frost action that in turn may break up naturally into fragments and particles of still smaller dimensions. 1. Exfoliation 2. Frost Wedging 3. Salt Wedging 4. Temperature Changes 5. Abrasion
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Mechanical Weathering
Mechanical Weathering: Frost Wedging
Frost Action Frost Action: water on freezing undergoes an increase in its volume by about ten per cent. This expansion is accompanied by exertion of pressure at the rate of 140 kg/cm2 (2000 lbs/in2) on the walls of the vessel containing the freezing water
Effects (Insolation): In arid, desert and semi-arid regions where summer and winter temperatures differ considerably, rocks undergo physical disintegration by another phenomenon related to temperature
Unloading: large-scale development of fracturing in confined rock masses is attributed to removal of the overlying rock cover due to prolonged erosional work of other agencies Table of Contents
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Mechanical Weathering: Abrasion
Temperature Changes
Abrasion occurs when rocks collide against each other while they are transported by water, glacial ice, wind, or gravitational force. The constant collision or gravitational falling of the rocks causes them to slowly break apart into progressively smaller particles.
Daily (diurnal) and seasonal temperature changes affect certain minerals and facilitates the mechanical weathering of bedrock. Warmer temperatures may cause some minerals to expand, and cooler temperatures cause them to contract.
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Flowing water is the primary medium of abrasion and it produces the ‘rounded’ shape of fluvial sediments.
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Chemical Weathering
Types of Chemical Weathering
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Chemical weathering decomposes, dissolves, alters, or weakens the rock through chemical processes to form residual materials.
Carbonation Hydrolysis Hydration Oxidation Solution
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Process of alteration of rocks of the crust by chemical decomposition brought about by atmospheric gases and moisture. The chemical change in the nature of the rock takes place in the presence of moisture containing many active gases from the atmosphere such as carbon dioxide, nitrogen, hydrogen and oxygen. Rocks are made up of minerals all of which are not in chemical equilibrium with the atmosphere around them Essentially a process of chemical reactions between the surfaces of rocks and the atmospheric gases in the direction of establishing a chemical equilibrium
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Chemical Weathering: Carbonation Carbonation is a process by which carbon dioxide and rainwater or moisture in the surrounding environment chemically react to produce carbonic acid, a weak acid, that reacts with carbonate minerals in the rock. This process simultaneously weakens the rock and removes the chemically weathered materials. Carbonation primarily occurs in wet, moist climates and effects rocks both on and beneath the surface. Carbonation occurs with limestone or dolomite rocks and usually produces very fine, clayey particles.
Limestone weathered by carbonation processes
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Chemical Weathering: Hydrolysis Hydrolysis is a chemical reaction between H+ and OH- ions in water and the minerals in the rock. The H+ ions in the water react with the minerals to produce weak acids. The reaction creates new compounds which tend to be softer and weaker than the original parent rock material. Hydrolysis can also cause certain minerals to expand, which also facilitates mechanical weathering processes. Hydrolysis commonly affects igneous rocks because they are composed of silicate minerals, such as quartz and feldspar, which readily combine with water. Hydrolysis may also be accompanied by hydration and oxidation weathering processes. The hydrolysis of feldspars produces kaolinite, which is a clay.
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The weathering rinds shown on this sample of amphibolite illustrate the effects of hydrolysis weathering on deposited rock fragments fragments.. Geologists measure the ‘thickness’ of the weathering rinds on in in--situ rock fragments to estimate the relative age of depositional landforms such as river terraces or alluvial fans fans.. The thicker the weathering rinds, the older the landform.. landform
Chemical Weathering: Hydration Hydration is a process where mineral structure in the rock forms a weak bond with H2O which causes the mineral grains to expand, creating stress which causes the disintegration of the rock. Hydration often produces a new mineral compound that is larger than the original compound. The increased size expanse the rock and can lead to decay.
Lead to color changes in the weathered rock surface.
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Oxidation occurs when oxygen and water react with iron-rich minerals and weaken the structure of the mineral. During oxidation the minerals in the rock will change colors, taking on a ‘rusty’, reddish-orange appearance. Similar to other chemical weathering processes, oxidation accelerates rock decay, rendering it more vulnerable to other forms of weathering.
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Chemical Weathering: Hydrolysis
This boulder is surrounded by saprolitic soils formed by the weathered rock. Hydration processes cause the formation of clays and contribute to the reddish-tan color of the saprolite.
Subsurface dissolution of halite has caused overlying rocks to collapse and form craterlike features.
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Chemical Weathering: Solution Solution occurs when minerals in rock dissolve directly into water. Solution most commonly occurs on rocks containing carbonates such as limestone, but may also affect rocks with large amount of halite, or rock salt. Solution of large areas of bedrock may cause sinkholes to form, where large areas of the ground subside or collapse forming a depression.
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This is an example of a limestone solution karst feature found in Florida's Everglades National Park
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Chemical Weathering- Types
Chemical Weathering- Types
a. Solution : Soluble in water for some extent b. Hydration and Hydrolysis : Direct attack of atmospheric moisture on the individual minerals of a rock that ultimately affect its structural make up c. Oxidation and Reduction :
d. Carbonation: It is the process of weathering of rocks under the combined action of atmospheric carbon dioxide and moisture, which on combination form a mildly reacting carbonic acid.The acid so formed exerts an especially corrosive action over a number of silicate bearing rocks. e. Colloid Formation: The processes of hydration, hydrolysis, oxidation and reduction operating on the rocks and minerals under different atmospheric conditions may not always end in the formation of stable end products
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a. Oxidation: Ferrous iron (Fe++) of the minerals is oxidized to ferric iron (Fe+++) on exposure to air rich in moisture. Ferric iron is not stable and is further oxidized to a stable ferric hydroxide b. Reduction: In specific types of environment, such as where soil is rich in decaying vegetation (swamps), minerals and rocks containing iron oxide may undergo a reduction o the oxides to elemental iron. In this case the decaying vegetation supplies the carbonaceous content causing reduction
Biological Weathering
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Tree Roots - Rock disintegration by plant growth Organic Acids - Secretion of acids Animal activity - Burrowing and tunneling organisms Organic activity from lichen and algae
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a. b. c. d.
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Usually consists of a combination of physical (growth of roots into joints in rocks) and chemical (e.g. impact of organic acids) processes.
Mr.T.Karthikeyan M.E (Geotech), AP/Civil, VSAGI Salem 10
Factors Affecting Weathering Nature of the Rock Some rocks are easily affected by weathering processes in a particular environment whereas others may get only slightly affected and still others may remain totally unaffected under the same conditions. Climate Cold and humid conditions favour both chemical and mechanical types of weathering, whereas in totally dry and cold climates, neither chemical nor mechanical weathering may be quite conspicuous (due to absence of moisture). Physical Environment Rocks directly exposed to the atmosphere affects the rate of weathering to good extent.
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Differential Weathering
Weathering rates will not only vary depending on the type of weathering process, whether it is mechanical, chemical, or biological, but they will also vary depending on the rock material that is being weathered. Some rocks are harder than other rocks, and will weather slower than softer rocks. The differences in rates of weathering due to different types of rocks, textures, or other characteristics is referred to as differential weathering. Differential weathering processes contribute to the unique formation of many landforms, including pedestals, waterfalls, and monadnocks. Climate can also produce differential weathering responses for the same rock type. For example, limestone weathers more quickly in wet climates than dry climates.
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Peachtree Rock’s unique pyramidal shape is a result of differential weathering associated with the different sedimentary sandstone rock components. The top portion of the outcrop consists of hard, coarsegrained sandstone, while the lower part of the rock consist of a less cohesive, sandstone layer. The lower portion of the rock has weathered more quickly than the upper portion ultimately producing its unique pyramidal shape.
Erosion
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W I N D
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GEOLOGICAL WORK OF
erodes rocks and the landscapes by transporting weathered materials from their source to another location where they are deposited. Wind erodes materials by picking them up and temporarily transporting them from their source to another location where they are deposited, and either stored or re-mobilized and transported to another location. Ice erosion occurs when particles are plucked up or incorporated by moving ice, such as a glaciers, and are transported downhill, or when friction between the ice and bedrock erodes materials and then transports them downhill. Gravity facilitates the down slope transportation of loosened, weathered materials and enables them to move without the aid of water, wind, or ice. Gravity related erosion is a major component of mass-wasting events.
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This basin and range landscape is influenced by several erosional processes. The mountains in the background are dissected by fluvial erosion (water) and the sandstorm in the valley is a form of aeolian (wind) erosion. The mountains may contain numerous rocks falls or landslides a form of gravity related mass-wasting erosion.
Erosion: Water (Fluvial)
Water erodes rocks and shapes the landscapes by removing and transporting weathered materials from their source to another location where they are deposited and either stored or transported to another location. Fluvial erosion is often broken into 3 distinct categories: rain-splash erosion, sheet erosion, and rill/gully erosion.
Rain splash erosion occurs when the impact of a rain drop loosens and mobilizes particles. Sheet erosion is a process where particles loosened buy rain-splash erosion are transported by runoff water down the slope of a surface. Rill erosion occurs when water concentrates during sheet erosion and erodes small rills or gullys into the surface that channel flow down slope.
Fluvial erosion can occur during rainfall events, from melt-water runoff, or ground water percolation. Materials being eroded and transported are either suspended in the water, bounced by saltation, or rolled along the ground by traction depending on a variety of conditions. The accumulation of fluvial erosion and associated processes over a large area forms pathways for surface and groundwater flow and carves v-shaped river valleys that continue to erode, transport, and deposit weathered sediments across the landscape.
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Erosion: Wind (Aeolian)
This drawing illustrates rain-splash impact on the soil and the erosion of individual grains of sediment..
Wind erodes weathered rocks by picking them up and temporarily transporting them from their source to another location where they are deposited, and either stored or re-mobilized and transported to another location Erosion by wind is divided into two different categories: Deflation and Abrasion Deflation is the movement or transport of particles through the air or along the ground Abrasion is the process that occurs when wind-transported particles sculpt features in the landscape through a “sandblasting” like process Aeolian erosion and deposition processes create a diversity of landforms including sand dunes, loess deposits, and yardangs.
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This satellite image captured a regional dust storm transporting aeolian sediments from Sudan and Africa over the Red Sea. In arid, desert climates wind erosion is very common and can transport sediments 100’s of miles before they are deposited.
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Courtesy Modis, Nasa
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The image shows the landscape scale effects of fluvial erosion
Erosion: Ice (Periglacial and Glacial) Ice erosion occurs in combination with periglacial and glacial processes Glacial erosion occurs when particles are incorporated into the glacial ice through a process referred to as plucking, and they are transported downslope within the glacier. The friction and abrasion of the ice and rock moving across the bedrock, erodes the surface of the bedrock and often leaves scrapes, grooves, striae, or polished rock surfaces. The cumulative effects of glacial erosion on a mountainous landscape can produce distinct u-shaped valleys which are a common glacial landform.
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Glacial erosion of this landscape has carved several distinct landforms, such as the glacial u-shaped valleys and the arêtes, which form the ridges between the ushape valleys.
Erosion: Gravity
Gravity facilitates the down slope transportation of loosened, weathered materials and enables them to move without the aid of water, wind, or ice. However, these agents can act as catalysts for gravity related erosion.
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Deflation
Mass Wasting
when wind is moving with sufficient velocity over dry and loose sands or bare ground over dust, it can remove or sweep away huge quantity of the loose material from the surface. This process of removal of particles of dust and sand by strong winds is called deflation. It is the main process of wind erosion in desert regions. In fact, in some deserts, deflation may cause the removal of sand from a particular location to such an extent that a big enough depression is created, sometimes with its base touching the water table at quite a depth.
Mass wasting is a rapid form of erosion that works primarily under the influence of gravity in combination with other erosional agents. Mass wasting occurs very quickly and can result in either small or large scale changes to the landscape depending on the type of event.
Rock Fall
Landslide
Much deeper and extensive depression where the water table is intersected and it gets partially filled up with water is called an O A S I S . Slack is another term used for such depressions created by deflation.
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Rock Falls Landslides Debris / Mud Flows Slumps Creep
Wind Abrasion
Yardangs. These are elongated, low-lying ridges forming overhangs above local depressions.
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Wind becomes a powerful agent for rubbing and abrading the rock surfaces when naturally loaded with sand and dust particles. This load is acquired by the strong winds quite easily when blowing over sand dunes in deserts and over the dry ploughed fields. This type of erosion involving rubbing, grinding, abrading and polishing the rock surfaces by any natural agent (wind, water or ice) with the help of its load while passing over the rocks is termed as abrasion.
Pedestal Rocks These are small sized rock fragments showing one, two or three or even more typically with polished surfaces called faces. Polished and faceted rock fragments are called. Ventifacts. Wind blowing in a particular direction, produce smooth and flat surfaces.
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Attrition by wind
Sand Dunes
The wind-borne particles, traveling in suspension do often have the chance of colliding with one another. Such mutual collision amongst themselves causes a further grinding of the particles and the process is described as attrition. The three processes of erosion, namely deflation, abrasion and attrition generally operate simultaneously under favourable conditions and causes appreciable degradation of the landmass on which they work.
Parabolic dunes:
Stream erosion is the greatest at waterfalls. waterfalls is called undermining.
Erosion at
Resistant rocks usually form steep cliffs and waterfalls, by sticking out further than the lower layers.
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Barchan dunes
Transportation by stream 1. Solution – the smallest particles of weathering are
dissolved in the water and they are transported in a solution.
2. Suspension – clay sized/colloids are carried along with
the water molecules during erosion. They are neither at the bottom or on the top. They are suspended in the middle of the running water.
3. Saltation( Rolling) – solid sediments are rolled and Running Water – sediments that have been transported through running water appear rounded and smooth and are deposited in sorted piles.
Mr.T.Karthikeyan M.E (Geotech), AP/Civil, VSAGI Salem 10
bounces along the bottom of a river stream because they are more dense.
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Potholes The sediments that are being transported by the river/stream are traveling a little bit slower than the water. This is because of friction.
The formation process for a pothole may be initiated by a simple plucking out of a protruding or outstanding rock projection at the riverbed by hydraulic action.
Stream/River Bed – the bottom of a stream or river.
This produces a small depression only at the place of plucking in the otherwise normal bedrock.
Bed Load – the material being transported along the bottom of a river/stream (rocks and pebbles).
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Downcutting – when weathering and erosion, along with the running water, cause the stream/river to become wider and deeper over time. Younger streams/rivers are more shallow and narrow. Older rivers/streams are wider and much deeper.
Meandering (Curving) River/Stream
Running Water
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Straight Flowing River/Stream
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Sediments are traveling the fastest in the center directly below the surface.
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Deposition happens on the inside of turns.
Erosion happens on the outside of turns.
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Deposition – the process where sediments are released /dropped by their agent of erosion. Most deposition happens in standing/still bodies of water (oceans/lakes). Deposition is caused by the slowing down (loss of kinetic energy) of the agent of erosion. There are 3 factors that influence the rate of sediment deposition: 1. Sediment size – 2. Sediment shape – 3. Sediment density -
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Graded Bedding/Vertical Sorting – a situation where larger particles settle on the bottom and smaller particles settle towards the top. This happens naturally when a fast moving river/stream meets a large standing body of water. This happens because the velocity of the water decreases very quickly. (A waterfall emptying into a lake)
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Horizontal Sorting – a situation where moving water enters a larger, still body of water slowly, and causes the larger particles to be deposited closer to the shoreline. Particle size decreases as you move away from the shore.
Delta – a fan shaped deposit that forms at the mouth of a river/stream when it enters a larger body of water. This is seen under the water. The particles are horizontally sorted.
Alluvial Fan
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A fan shaped deposit of sediments that forms when a stream/river flows out of a mountain on to flat, dry plains. These are not under water and are very visible. This only happens on the land. You can call it a “land delta”.
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Cross-Bedding – a situation where layers of sediments are deposited at angles to one another as a result of a change of direction of the erosional agent. These are usually found in sand dunes, deltas, and alluvial fans.
Mr.T.Karthikeyan M.E (Geotech), AP/Civil, VSAGI Salem 10
GEOLOGICAL WORK OF SEA It is well known that about 71 % of the surface of the earth is covered by the oceans and seas. The oceans and seas cover an area of about 361 million square kilometer out of 510 million square kilometer of the surface of the entire globe. The geological activity of seas and oceans, like other geological agents, comprises the processes of erosion, transportation and deposition, which depend on a large number of factors such as: (i) Relief of the floor. (ii) Chemical composition of the sea water. (iii) Temperature, pressure and density of sea water. (iv) Gas regime of seas and oceans. (v) Movement of sea water. vi) Work of sea organisms etc.
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Ocean Regions wards away from the shore.
Continental slope- From the edge of the continental shelf, the
sea floor commonly descends to the ocean basin, with an average gradient of 3.5° to 7.5° and is known as continental slope.
Continental rise - It extends from the bottom of the
continental slope to the floor of the ocean basins. The rise has a slope of 1° to 6°.
Ocean floor - It begins at a depth of 2000 meters and goes
Oscillatory waves: These are characteristics of deeper
portions of the sea .In such waves, each particle moves in a circular orbit. In shallow depths, these particles find it impossible to describe a perfectly circular motion. Consequently an oscillatory wave rushing towards the shore breaks at the crest region, giving rise to the so well known surfs.
Translatory Waves: These are typically of shallower depths
in the sea and abound along the seashore. They are commonly produced after the oscillatory waves break and rush forward.
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down to 6000 meters. It covers 76 per cent of the total area of the oceans and has a very gentle gradient, being measured in minutes. It contains a number of distinctive topographic units such as abyssal plains, seamounts and guyots, mid-ocean canyons, and hills and rises that project somewhat above the general level of the ocean basins.
Waves & Currents
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Continental Shelf- The ocean floor gradually slopes down
Sea Cliffs
These are layers or strips of seawater that are actually pushed forward in any particular direction. Two types are more important in the geological work of sea:
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Littoral Currents: These are bodies of seawater of
When the sea erodes an area of high ground to create a vertical face of rock or other material a cliff is formed. The sea creates a 'notch' at the base of the cliff causing the cliff to eventually collapse.
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Currents:
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considerable volume moving along and parallel to the shore. Rip Currents: These are bodies of seawater moving backwards to sea after having reached and struck the seashore. They often move below the surface of the sea and reach varying distance up to the middle of the sea.
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Wave-Cut Terraces
This is an area of relatively flat rock at the base of the cliff which has been created by the retreating shoreline.
Mr.T.Karthikeyan M.E (Geotech), AP/Civil, VSAGI Salem 10
Bays and Headlands If there are areas of soft and hard rock along the coastline the sea erodes the softer rock more quickly than the harder rock. This creates a wide inlet known as a bay. The harder rock is less affected by the erosion of the sea and remains as a headland.
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MARINE DEPOSITION BEACH A beach is an accumulation of sand, shingle or rock between the high tide mark and low tide mark. A beach forms if the incoming wave (Swash) is stronger than the out-going wave(Backwash) SandSpit A spit is a finger of land which grows out from the mainland, it is formed from sand and mud and other material deposited by the waves. Sand Bar A sand bar is formed when a sand spit grows across the mouth of a bay and cuts it off from the sea. The area of enclosed water becomes known as a lagoon. Tombolo A tombolo is formed when a sand spit links an off-shore island to the mainland.
SandSpit
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Tombolo
Introduction
Earthquake belts in India
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Earthquakes are movement of surface of earth caused by sudden release of energy within the earth’s crust.
Causes
Slip or fracture of rocks within the crust of earth Volcanic activity Collapse of roof of underground mine or cavern Underground detonation of chemical or nuclear devices Impounding of water in large reservoirs
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Earthquakes occur on a daily basis around the world but most of them are sufficiently small in size or occur due to tectonic activity deep inside the crust so as to cause any harm on the surface of the earth. Nearly 90% of the earthquakes are of tectonic origin.
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An earthquake (also known as a quake, or tremor) is a violent movement of the rocks in the Earth's crust. Earthquakes are usually quite brief, but may repeat over a long period of time. They are the result of a sudden release of energy in the Earth's crust. This creates seismic waves, waves of energy that travel through the Earth. The study of earthquakes is called seismology. Seismology studies the frequency, type and size of earthquakes over a period of time. When the earth moves offshore in the ocean, it can cause a tsunami. A tsunami can cause just as much death and destruction as an earthquake. Landslides can happen, too
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Consequences of Earthquake Earthquakes initiate a number of phenomena termed as seismic hazards, which can cause significant damage to the built environment like:
Vibratory ground motion(shaking) Inundation(e.g. tsunami, seiche, dam failure) Various kinds of ground failure(e.g. liquefaction, landslides Fire or leak of hazardous materials including nuclear radiations.
Even though earthquakes last for only few seconds or minute, the impression it leaves behind on the community are long lasting. Over the last century it has been observed that 75% of fatalities attributed to earthquakes have been caused by collapse of buildings. In spite of the steady progress made in understanding the earthquake processes in the last fifty to sixty years, prediction of the earthquakes is still elusive.
Mr.T.Karthikeyan M.E (Geotech), AP/Civil, VSAGI Salem 10
Continental drift theory and plate tectonics The continental drift theory proposed in the early twentieth century by Taylor and Wegener. The entire earth was one large continent called Pangaea about 200 million years ago. Pangaea broke into a number of pieces and slowly drifted to reach the present configuration of continents. Lithosphere is divided into about 14 large sized rigid plates. Resting on a relatively soft upper portion of the mantle called as asthenosphere. Due to temperature variation between the centre of the earth(core) and the crust; convectional currents are setup which is responsible for the constant motion of the plates.
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Continental drift theory and plate tectonics
Shows the major tectonic plates of earth and their direction of movement
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The movement of the plates is relative to each other and depending on the direction of relative movement of the plates three distinct types of plates boundaries have been identified.
Elastic rebound theory According to this due to relative movement of the plates, the material of the plates adjacent to its boundaries gets strained as the friction or interlocking between the adjacent plates prevents their movement. As a result of this constraint shear stresses developing the plates in the vicinity of their boundaries over a period of time and accumulate strain energy. Ultimately when shear stresses exceed the frictional force or the shear strength of the rocks, the plates slip or rupture releasing the stored energy. If the plate material is strong and brittle the failure will be rapid and the stored energy will be released explosively partly in the form of heat and partly in form of stress waves which are felt as earthquakes.
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Shows global map indicating seismic events across the globe for the last fifty years
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Some Megathrust Earthquakes
Some of the examples of megathrust earthquakes are: 1700 Cascadian earthquake(magnitude 9.0) 1737 Kamchatka earthquake(magnitude 9.3) 1755 Lisbon earthquake(magnitude~9) 1952 Andreanof islands earthquake(magnitude 9.3) 1960 Great Chilean earthquake(magnitude 9.3) 1964 Good Friday earthquake(magnitude 9.3) 2004 Indian ocean earthquake(magnitude 9.3)
Devastating earthquakes have also occurred within a plate, away from the boundaries and such earthquakes are called as intraplate earthquakes. Examples of intraplate earthquakes are:
1812 New Madrid(Missouri) earthquake(magnitude 8) 1886 Charleston(South California) earthquake(magnitude 6.6-7.3) 1976 Tangshan(China) earthquake(magnitude 7.8) 1993 Latur(India) earthquake(magnitude 6.2) 2001 Bhuj(India) earthquake(magnitude 7.9)
Mr.T.Karthikeyan M.E (Geotech), AP/Civil, VSAGI Salem 10
Seismic waves
The energy released by the earthquake gets propagated in a form of waves known as seismic wave. Seismic waves are broadly classified into two Body waves: Body waves travel through the interior of the earth. primary waves (P-waves) secondary waves(S-waves) surface waves: They are generated due to interaction of body waves with the stratified formations of the earth’s crust. love waves Rayleigh waves
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Seismic waves
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Epicentre It is the point on the surface of the earth, vertically above the place of origin (hypocenter) of an earthquake. This point is expressed by its geographical Coordinates in terms of latitude and longitude. Hypocenter or Focus It is the point within the earth, from where seismic waves originate. Focal depth is the vertical distance between the Hypocenter (Focus) and Epicenter. Magnitude It is a quantity to measure the size of an earthquake and is independent of the place of the observation.
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Seismology Is the science of Earthquakes and related phenomena. Seismograph/ Seismogram Seismograph is an instrument that records the ground motions. Seismogram is a continuous written record of an earthquake recorded by a seismograph. Seismometer device for detecting seismic waves
CLASSIFICATION OF EARTHQUAKE
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TABLE 1.1 CLASSIFICATION OF EARTHQUAKES
Category
Magnitude on Richter Scale
Slight
Up to 4.9
Moderate
5.0 to 6.9
Great
7.0 to 7.9
Very Great
8.0 and more
Natural earthquakes- natural forces Tectonic earthquakes
Tectonic earthquakes are caused by the sudden earth movements, generally along faults, usually at depths varying from about 4.5 km to 24 km below the earth's surface.
Plutonic earthquakes
Plutonic earthquakes are deep focus earthquakes, the depth of disturbances being between 250 km and about 700 km.
Volcanic earthquakes
Volcanic earthquakes are associated with explosive eruption of volcanoes.
Artificial earthquakes - human activities
Mr.T.Karthikeyan M.E (Geotech), AP/Civil, VSAGI Salem 10
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市场分析图
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Mr.T.Karthikeyan M.E (Geotech), AP/Civil, VSAGI Salem 10
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Thank You
Kingsoft Office
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Make Presentation much more fun
Mr.T.Karthikeyan M.E (Geotech), AP/Civil, VSAGI Salem 10
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