ENGINEERING GEOLOGY - INTRODUCTION Engr. Imran Mehmood Civil Engineering Department Swedish College of Engineering & Technology, Wah Cantt Date # 26th December, 2011 – Lecture # 04

GEOLOGY “Geology is the study of the Earth, including the materials that it is made of, the physical and chemical changes that occur on its surface and in its interior, and the history of the planet and its life forms” Physical Geology – “Examines the materials and processes of the Earth” Historical Geology – “Examines the origin and evolution of planets through time” Engineering Geology – “Application of geological data, techniques and principles to the study of rock and soil surfacing materials, and ground water” Seismology – “study of the generation, propagation and recording of the elastic waves and the source that produce them”

ENGINEERING GEOLOGY IN CIVIL ENGINEERING Civil engineers design structures that are built on or in the ground. As such an understanding of how the ground behaves is fundamental to civil engineering design. Earth materials can pose significant problems that need to be predicted, planned and designed for: Foundation Engineering - assessment of soil conditions Construction Materials Engineering - quality of stones, lime, cement etc Infrastructure Engineering - location of bridges, tunnels, river meandering zones Disaster Mitigation - seismic resistant structural design, flood control, river training, waterway of bridges Water Resources Engineering - hydrogeology (reservoir capacity for e.g.), source and quality of aquifer and water

Origin of earth Most researchers believe that Earth and the other planets formed at essentially the same time: Nebular Hypothesis 5 billion years ago, formation of diffuse and frozen cloud (of dust & gas) from the explosion of star. Consisted of Hydrogen and Helium (abundant in universe) Temperature of the cloud was about 270˚C. Gravitational attractions caused the cloud condense into sphere As condensation continued, cloud rotated more rapidly, the sphere spread into disk At this stage, cloud collapsed towards centre (under gravity influence) and formed proto-sun

Origin of earth Nebular Hypothesis Heat from the proto-sun warmed the inner region of the disk. When collapsed was completed, disk get cooled and gases at outer part of disk condensed to form small aggregates With time aggregates stuck together, increased in size and developed stronger gravitational forces G. Forces lead to formation of rocky spheres called planet-esimals (ranging upto 100km in dia) Heat of the sun have boiled/removed gases away from the inner solar system, that’s why Mercury, Venus, Earth & Mars are rocky planets (terrestrials, Earthlike)

Origin of earth Nebular Hypothesis

A view of earth INTERNAL PROCESSES Processes that originate deep in the earth’s interior. These are the driving forces that raise mountains, cause earthquakes and produce volcanic eruptions. Builders, Engineers and Town Planners might consult geologists, asking “What is the probability that an earthquake or volcanic eruption can damage our city? Is it safe to build sky scrappers, a dam or a nuclear based project in the area?”

Origin of earth EXTERNAL PROCESSES ATMOSPHERE Air Contains all the air in Earth’s system. Origin of earth BIOSPHERE Living Things Contains all of Earth’s living things— microorganisms, plants, and animals. LITHOSPHERE Land Contains all the cold, hard, solid land of Earth’s crust (surface), the semi-solid land underneath the crust, and the liquid land near the center. HYDROSPHERE Water Contains all the solid, liquid, and gaseous water of Earth.

INTERNAL STRUCTURE OF earth Layers Defined by Composition Crust Mantle Core Layers Defined by Physical Properties Lithosphere Asthenosphere Mesosphere Inner & Outer Core

INTERNAL STRUCTURE OF earth

EARTH LAYERS CRUST Outermost and the thinnest layer of earth. Consist of relatively hard, brittle and strong rocks (fractures under earthquake) Crust has normally two types of thicknesses; under the oceans has thickness 5km to 10km (Oceanic Crust) and under the land masses, its thickness is about 10km to 40km (Continental Crust). However, under mountains it has thickness up to 70km. The eggshell analogy for the crust is not an exaggeration, as it is paper thin compared to the radius of earth, 6400km. Total weight of continental crust is less than 0.3% of whole earth.

EARTH LAYERS MANTLE Lies directly below the earth crust. Its almost 2900km thick and make up 80% of the earth’s volume. Chemical composition of mantle may remain same, but due to a lot of variation in temperature and pressure with the depth, which causes the strength of mantle to vary with the depth. Which creates layering within the mantle. These layers are as follows: Lithosphere Asthenosphere Mesosphere

EARTH LAYERS MANTLE → LITHOSPHERE The uppermost mantle is relatively cool and consequently hard, strong rock. The outer part of earth including both upper mantle and crust make up the lithosphere (Greek=Rock Layer). Can be thin as 10km. However it ranges from 75km under the oceans to 125km under the continents.

EARTH LAYERS MANTLE → ASTHENOSPHERE At a depth of 75km to 125km lithosphere changes in asthenosphere, which is weak and less hard as compared to lithosphere. 1-2% of asthenosphere is liquid where the temperature is close to the melting point of rocks. It flow rate is few cm/yr as it is plastic. Extends from the base of lithosphere to 350km. MANTLE → MESOSPHERE It is lowest layer of mantle Its stiffness lies between lithosphere and asthenosphere.

EARTH LAYERS CORE Core is the innermost of the earth layers having a radius of 3470km and largely composed of iron and nickel. CORE → OUTER It is in molten state due to high temperature above melting point. Its thickness is below the base of mantle up to 2300km CORE → INNER It is in solid state, pressure at its centre is almost 1 million times that is at the sea level, which dominates over the temperature of about 6000˚C. Its thickness is about 1100km

INTERNAL STRUCTURE OF earth

EARTH STATISTICS Mass (kg) 5.976e+24 Mass (Earth = 1) Equatorial radius (km) 6,378.14 Equatorial radius (Earth = 1) 1.0 Mean density (gm/cm^3) 5.515 Mean distance from the Sun (km) 149,600,000 Rotational period (days) 0.99727 Rotational period (hours) 23.9345 Orbital period (days) 365.256 Mean orbital velocity (km/sec) 29.79 Orbital eccentricity 0.0167 Tilt of axis (degrees) 23.45 Orbital inclination (degrees) 0.000 Equatorial escape velocity (km/sec) 11.18 Equatorial surface gravity (m/sec^2) 9.78 Visual geometric albedo 0.37 Mean surface temperature 15°C Atmospheric pressure (bars) 1.013 Atmospheric composition Nitrogen 77 Oxygen 21 EARTH STATISTICS

THANK YOU Engr. Imran Mehmood Civil Engineering Department Swedish College of Engineering & Technology, Wah Cantt Date # 26th December, 2011 – Lecture # 04