Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

Interior of earth


Published on

interior structure of the earth

Published in: Engineering, Technology, Business
  • Be the first to comment

Interior of earth

  1. 1. by: muhammad adil mining engineering UET Peshawar EARTH STRUCTURE 1
  2. 2.  The study of the passage of seismic (earth quack) waves through the earth have helped greatly in knowing the interior of the earth.  The interior structure of the Earth is layered in spherical shells, like an onion. Earth has an outer silicate solid crust, a highly viscous mantle, a liquid outer core that is much less viscous than the mantle, and a solid inner core. EARTH STRUCTURE 2
  3. 3.  The structure of Earth can be defined in two ways: by mechanical properties such as rheology ( the study of the flow of matter, primarily in the liquid state) , or chemically.  Mechanically, it can be divided into lithosphere, asthenosp here, mesospheric mantle, outer core, and the inner core.  The interior of Earth is divided into 5 important layers. Chemically, Earth can be divided into the crust, upper mantle, lower mantle, outer core, and inner core. EARTH STRUCTURE 3
  4. 4.  At depth of 30 to 40 km, the velocity of both P and S waves increase abruptly. The velocity of p waves increases from about 6.5 km per second to about 8 km per second. This discontinuity surface is called the “mohorvicic discontinuity”.  Ta depth of 2900 km, from the Mohorvicic discontinuity to a depth of 2900 km, the velocity of both P and S wave increases gradually. But at 2900 km the P waves are sharply reflected and refracted, and their velocity drops abruptly from about 13 km per second to about 8 km per second.  The S waves are lost entirely. This discontinuity surface separates the “mantle” of the earth from the “core”.  At depth of 5000 km below the earth’s surface, there is an abrupt increase in the velocity of P waves. This discontinuity surface suggests the existence of an “inner core”. EARTH STRUCTURE 4
  5. 5.  The core is situated from 2900 km depth up the centre of the earth (6370 km ).  Since the S waves do not pass through the core. Seismic measurements show that the core is divided into two parts, a "solid" inner core with a radius of ~1,220 km and a liquid outer core extending beyond it to a radius of ~3,400 km.  The densities are between 9,900 and 12,200 kg/m3 in the outer core and 12,600– 13,000 kg/m3 in the inner core. The inner core was discovered in 1936 by Inge Lehmann and is generally believed to be composed primarily of iron and some nickel. EARTH STRUCTURE 5
  6. 6.  The inner core is believed to consist primarily of a nickel-iron alloy known as NiFe: 'Ni' for nickel, and 'Fe' for ferrum or iron. Because the inner core is denser (12.8 ~ 13.1)g⁄cm³ than pure iron or nickel, even under heavy pressures.  Earth's outer core is a liquid layer about 2,266 km (1,408 mi) thick composed of iron and nickel that lies above Earth's solid inner core and below its mantle. Its outer boundary lies 2,890 km (1,800 mi) beneath Earth's surface. The transition between the inner core and outer core is located approximately 5,150 km (3,200 mi) beneath Earth's surface.  The temperature of the outer core ranges from 4400 °C (8000 °F) in the outer regions to 6100 °C (11000 °F) near the inner core. Because of its high temperature, modeling work has shown that the outer core is a low viscosity fluid (about ten times the viscosity of liquid metals at the surface) that convects turbulently. EARTH STRUCTURE 6
  7. 7.  The mantle lies beneath the earth’s crust and it extends to a depth of 2,890 km, making it the thickest layer of Earth. The pressure at the bottom of the mantle is ~140 GPa (1.4 Matm). The mantle is composed of silicate rocks that are rich in iron and magnesium relative to the overlying crust. Although solid, the high temperatures within the mantle cause the silicate material to be sufficiently ductile that it can flow on very long timescales. It has been divided into the upper mantle and lower mantle. The upper mantle lies between 35 km and 1000 km depth, and is made up of ultra basic rocks like peridotite ( sp. Gr. 3.3) the lower mantle is between 1000 km and 2890 km, and contains pallasite (sp. Gr. 5.7) which is a mixture of basic rocks and metallic iron. EARTH STRUCTURE 7
  8. 8.  The outer most layer of solid rock, which lies above the Mohorovicic discontinuity and has an average thickness of 35 km, is known as the crust of the earth. Under the continents it is possible to distinguish two layers in the earth crust. The upper layer which is less dense (sp. Gr. 2.65) and granitic in character is known as the “sial” ; while the lower layer which is basaltic in character (sp. Gr. 3.0) is known as “sima”. The term sial represents rock rich in silica and alumina, and term sima represents rock containing silica and magnesia. Under oceans only sima layer is found and the sial layer appears to be absent. EARTH STRUCTURE 8