1 Earth_240513_060359.pdf

ST01502 EARTH SCIENCE (SAINS BUMI) THE EARTH  *ZI – DR ZULHERRY ISNAIN *MFA : DR MOHD AL-FARID ABRAHAM Lecture Syllabus Lecturer 1 The Earth...

ST01502 EARTH SCIENCE (SAINS BUMI) THE EARTH  *ZI – DR ZULHERRY ISNAIN *MFA : DR MOHD AL-FARID ABRAHAM Lecture Syllabus Lecturer 1 The Earth ZI 2 Plate Tectonics ZI 3 Minerals and Rocks ZI 4 Igneous Rocks ZI 5 Volcanism ZI 6 Metamorphic Rocks ZI 7 Mid Term ZI 7 Sedimentary Rocks, Weathering and Erosion MFA 9 Earthquakes and Seismology MFA 10 Faults and Folds MFA 11 Relative and Absolute Dating MFA 12 Surface Water MFA 13 Groundwater MFA 14 Case study MFA http://arboleda2016.blogspot.com/2010/09/social-studies-global-grid.html  The earth mass: 5.976 X 1024 kg. Earth's average distance from the Sun is 1.496 X 1011m, a distance known as the astronomical unit. The Earth is the third planet from the sun, certainly the most familiar planet, the average density is 5.52 g/cc. Solar day is 24 hours or 86,400 sec. The sidereal day, which is the Earth's rotational period relative to the "fixed" stars, is 23 hours, 56 minutes, and 4.1 seconds (or 86164.10 seconds) Earth's atmosphere is divided into five layers: exosphere (500 km and up), thermosphere (80-500 km; which includes the ionosphere), mesosphere (50-80 km), stratosphere (10-50 km) and troposphere (0-10 km). The atmosphere is composed of the following gases: Nitrogen, Oksigen, Argon, Water, Carbon dioxide, Neon, Ozone, Helium, Methane, Crypton, Helium, Hydrogen, Nitrogen dioxide, Carbon monoxide.  Chemical composition of the Earth The overall composition of the Earth is dominated by the elements iron (Fe), oxygen (O), silicon (Si), magnesium (Mg), nickel (Ni) and sulfur (S). This is because most of the mass of the Earth occurs within the mantle which is composed largely of the ferromagnesium silicate minerals olivine and pyroxenes. The overall composition of the Earth is very similar to that of meteorites, and because of this, it is thought that the Earth originally formed from Planetesimals composed largely of metallic iron and silicates. Bulk composition of the Earth Element Symbol Percent Iron Fe 34.6 Oxygen O2 29.5 Silica Si 15.2 Magnesium Mg 12.7 Nickel Ni 2.4 Sulfur S 9.0 Titanium Ti 0.05 the solid earth composed principally of rock at and below the Earth surface. Consists of igneous, sedimentary, and metamorphic rocks – Igneous - formed by cooling of magma – Sedimentary - formed by consolidation of loose sediment or by chemical precipitation from water – Metamorphic - igneous or sedimentary rocks that have been subjected to high temperature and/or pressure The Earth's Internal Structure Evidence from seismology tells us that the Earth has a layered structure. Seismic waves generated by earthquakes travel through the Earth with velocities that depend on the type of wave and the physical properties of the material through which the waves travel. Types of Seismic Waves – Body Waves - travel in all directions through the body of the Earth. There are two types of body waves, P- waves and S- waves – Surface Waves - Surface waves differ from body waves in that they do not travel through the Earth, but instead travel along paths nearly parallel to the surface of the Earth. Body Waves P - waves - are Primary waves. They travel with a velocity that depends on the elastic properties of the rock through which they travel. Vp =  [(K + 4/3µ )/ρ] Where, Vp is the velocity of the P-wave, K is the incompressibility of the material, µ is the rigidity of the material, and ρ is the density of the material. P-waves are the same thing as sound waves. They move through the material by compressing it, but after it has been compressed it expands, so that the wave moves by compressing and expanding the material as it travels. Thus the velocity of the P-wave depends on how easily the material can be compressed (the incompressibility), how rigid the material is (the rigidity), and the density of the material. P-waves have the highest velocity of all seismic waves and thus will reach all seismographs first. Body Waves S-Waves - Secondary waves, also called shear waves. They travel with a velocity that depends only on the rigidity and density of the material through which they travel: Vs =  [( µ )/ρ ] Where, Vs is the velocity of the S-wave, µ is the rigidity of the material, and ρ is the density of the material. S-waves travel through material by shearing it or changing its shape in the direction perpendicular to the direction of travel. The resistance to shearing of a material is the property called the rigidity. It is notable that liquids have no rigidity, so that the velocity of an S-wave is zero in a liquid. S-waves travel slower than P-waves, so they will reach a seismograph after the P-wave. Surface Waves – ▪ Surface waves differ from body waves in that they do not travel through the Earth, but instead travel along paths nearly parallel to the surface of the Earth. ▪ Surface waves behave like S-waves in that they cause up and down and side to side movement as they pass, but they travel slower than S-waves and do not travel through the body of the Earth. ▪ Thus they can give us information about the properties of rocks near the surface, but not about the properties of the Earth deep in the interior. ▪ Once we know the seismic wave velocities throughout the Earth, then we can perform experiments on different possible materials and make estimates of what the chemical composition. Thus, we can also divide the Earth into layers of differing chemical composition This table of depths, densities, and composition is derived mostly from information in a textbook by Don L. Anderson (see Suggested Reading). Scientists are continuing to refine the chemical and mineral composition of the Earth's interior by laboratory experiments, by using pressures 2 million times the pressure of the atmosphere at the surface and temperatures as high as 20000 C.  The Crust The crust makes up only 0.5 % of the Earth's total mass Can be subdivided into two main parts, continental and oceanic. Both differ in thickness, density and composition. The oceanic crust covers approximately 61 % of the Earth's surface, but only comprises some 30 % of the crustal mass, The continental crust is much thicker, up to 70 km. Because the crust is accessible to us, its geology has been extensively studied, and therefore much more information is known about its structure and composition compare to the mantle and core. Within the crust, intricate patterns are created when rocks are redistributed and deposited in layers through the geologic processes of eruption and intrusion of lava, erosion, and consolidation of rock particles, and solidification and recrystallization of porous rock.  The Mantle As seismic velocity change through the mantle, we can subdivide it into an upper mantle, transition zone, and lower mantle. There is also a zone in the upper mantle that we call the low velocity zone (located at depths of 70 km to 250 km) where S-wave speeds decrease rapidly to a minimum and then gradually increase again. We believe that most magmas (molten rock) are generated in this zone. – Upper mantle (measured from the base of the crust down to 400 km). 10 % of the Earth's total mass. Density of 3.25 gm/cm3 to 3.40 gm/cm3 Composition: – Peridotite (e.g. olivine + pyroxene) along with plagioclase (< 30 km depth), – spinel (30 km - 70 km depth) and garnet (> 70 km depth). In tectonically active regions, eclogite (amphibole + garnet) is a major component. Although it is thought that almost all basalts are derived from the upper mantle, experiments have shown that their compositions cannot be formed by the partial melting of peridotite alone. The upper mantle therefore is probably composed of two main zones: an upper peridotite zone and an underlying primitive mantle or pyrolite zone composed of pyroxene, olivine, and/or garnet and/or plagioclase, where basaltic magmas are generated. – Transition zone (400 km - 1000 km below the Earth's surface). 17 % of the Earth's total mass. The top of the transition zone is marked by the phase transformation of normal olivine to a proto-spinel structure polymorph of olivine which is a higher pressure phase and is 9 % denser than normal olivine and by the phase transformation of normal pyroxene to a garnet-structure polymorph of pyroxene. Within the transition zone itself, there are a number of irregular seismic velocity changes including a major one at 680 km which is marked by the breakdown of olivine into its constituent oxide components of periclase (MgO) and stishovite (SiO2). Also, garnet is broken-down to its component oxides from 680 km - 1000 km. – Lower mantle (1000 km - 2900 km below the Earth's surface). 41 % of the Earth's total mass. The lower mantle is a region of relatively low seismic velocity gradients. It most likely consists of mixed oxides of pyrolite composition but with an increased iron content.  Core The core was the first internal structural element to be identified by R.D. Oldham in 1906 from his study of earthquake records, and it helped to explain Newton's calculation of the Earth's density. The outer core is presumed to be liquid because it does not transmit shear (S) waves and because the velocity of compressional (P) waves that pass through it is sharply reduced. The inner core is considered to be solid because of the behavior of P and S waves passing through it. The earthquake waves paths curve because the different rock types found at different depths change the speed at which the waves travel. Solid lines marked P are compressional waves; dashed lines marked S are shear waves. S waves do not travel through the core but may be converted to compressional waves (marked K) on entering the core (PKP, SKS). Waves may be reflected at the surface (PP, PPP, SS). The core is presumed to be composed principally of iron, with about 10 percent alloy of oxygen or sulfur or nickel, or perhaps some combination of these three elements. Outer core (2900 km - 5000 km below the Earth's surface). 30 % of the Earth's total mass. Inner core (5000 km - 6370 km below the Earth's surface). 2 % of the Earth's total mass. THANK YOU ☺