Marine Environment (Oceanography Geology) PDF

MARINE ENVIRONMENT Oceanography Geology Sub-topics: Earth internal structure Plate tectonic Seafloor features Marine sediments Internal Structure of the Earth Internal Structure of the Earth You will learn about: - External shape of the Earth - Internal structure and various...

MARINE ENVIRONMENT Oceanography Geology Sub-topics: Earth internal structure Plate tectonic Seafloor features Marine sediments Internal Structure of the Earth Internal Structure of the Earth You will learn about: - External shape of the Earth - Internal structure and various layers - Crust, Mantle, Core - Discontinuities (e.g. Moho, Gutenberg, Lehmann) - Evidence of Earth’s interior structure  Fundamental particles formation (13.7 BY ago) Galaxies and Star formation Solar System External shape of the Earth The earth is not quite a perfect sphere but an ‘oblate’ (bun shaped) ellipsoid close to that of an ideal fluid drop rotating at the same velocity as the Earth. There is more mass along the equatorial diameter than the polar diameter.  External shape of the Earth Perfect circle (~43 km shorter) The earth is not quite a perfect sphere but an ‘oblate’ (bun shaped) ellipsoid close to that of an ideal fluid drop rotating at the same velocity as the Earth. There is more mass along the equatorial diameter than the polar diameter.  Earth’s Interior Core ▪ dense ▪ Iron and Nickel Crust ▪ Inner Core - solid ▪ Outer Core - Upper Mantle liquid Mantle Lower Mantle ▪ Less dense than core Outer Core Inner ▪ Iron and Magnesium silicates Core ▪ Mostly solid ▪ Upper mantle is partially molten Crust ▪ Outermost layer ▪ Very thin and rigid ▪ Continental – granite ▪ Density = 2.8 g/cm3 ▪ Oceanic – basalt ▪ Density = 3.0 g/cm3  Small Formation of Earth’s layers The Earth formed through accretion, undifferentiated Absorbing planetisimals (lumps of rock Undifferentiated bodies and ice? through collisions. bodies Earth may be accreted material that undifferentiated then shell and separatedthat material then shell andseparated core and reach its present into form differentiating Core before. formation formation Alternatively, might inside core growing have combination theseof happene formed cores. previous planetisimals, d so thelyEarth’s core is Differentiated Present Earth bodies with cores Minarik (2003), Nature  Internal Structure of the Earth Mountain Sediment Sea The interior structure of the Earth is layered in spherical shells, like an onion. The interior of Earth is divided into several layers. Chemically, Earth can be divided into 5 layers such as the crust, upper mantle, lower mantle, outer core 0 Crust and inner core. Mantle 6371 km Core Earth  Internal Structure : The Crust Sediment Basalt Granite Sea Oceanic crust Continental crust (5 ~ 10 km) (30~70 km) The crust is the outermost solid shell of the Earth, which is chemically distinct from the underlying mantle. The crusts of Earth have been generated largely by igneous processes, and these crusts are richer in incompatible elements than their respective mantles. The crust of Earth’s occupies less than 1% volume and is devided into oceanic and continental crust. The outermost shell of a rocky planet is defined on the basis of its chemistry and mineralogy.  The Crust: Explained Basalt Granite ] ] Crust Oceanic crust is a thin part of the earth's crust that underlies the ocean basins. It is geologically young compared with the continental crust and consists of basaltic rock overlain by sediments. Continental crust is a thick part of the earth's crust that forms the large landmasses. It is generally older and consists of many rock types including granite as a dominant rock. Below the Earth’s crust lies the mantle. Lithosphere is the rigid outer part of the earth, consisting of the crust and upper mantle.  Moho Discontinuity Sediment Sea Lithosphere (Crust+ upper mantle) Moho The boundary between the Earth’s crust and Discontinuity mantle is called the Moho discontinuity and Average ~ 35 is defined by a contrast in seismic velocity. It km below the crust. separates both the oceanic crust and continental crust from underlying mantle. The Moho lies from 5 to 10 km below the ocean floor and 20 to 90 km beneath the continents. A lithosphere is the rigid, outermost shell and comprises the crust and the portion of the upper mantle that behaves elastically. The Moho lies almost entirely within the lithosphere.  The Mantle Sediment Sea The mantle is a layer inside the Earth and lies between the outer Lithosphere core and the crust above. Earth's mantle is a silicate shell with an average thickness of 2,800 km. Asthenosphere The mantle makes up about 84% of Earth's volume. It is predominantly solid but in geological time it behaves as a viscous fluid. Earth’s mantle is chemically divided into two layers; upper mantle and lower mantle.  Lithosphere and Asthenosphere Sediment Sea Lithosphere The lithosphere is the rigid outer 70~150 km part of the earth, consisting of the of crust and a part of the upper mantle. Asthenosphere The asthenosphere is highly 150 ~700 km viscous, mechanically weak and deforming region of the upper mantle of the Earth. It is the upper layer of the earth's mantle and below the lithosphere.  Gutenberg Discontinuity Sea Sediment Gutenberg discontinuity represents the core-mantle of the Earth boundary (CMB)and lies between Lithosphere the mantle, the lower iron-nickel liquid and outer core. This boundary is located at Asthenosphere approximately 2880 km depth beneath the Earth's surface. The boundary is observed via the Gutenberg discontinuity in seismic wave Discontinuity velocities at that depth. At this depth, primary seismic waves (P waves) decrease in velocity while secondary seismic waves (S waves) disappear completely.  The Core Sediment Sea The outer core of the Earth is a liquid layer about 2,300 km thick and composed of iron and nickel that lies above Earth's solid inner core and below its mantle. Its outer boundary lies 2,880 km beneath Earth's surface. The transition between the inner core and outer core is located approximately 5,155 km beneath the Earth's surface. The inner core the Earth's innermost and it is ball primarily is with a radius of about part 1220 km. It is believed toa consist primarily of an iron–nickel alloy. 6371 km solid Outer Core and Earth’s magnetic field The Earth has a magnetic field and acts as a giant bar magnet. Scientists believe that the outer movements Earth’s liquid core create Earth’s magnetic field. It is the earth’s field magnetic that protects us from the harmful effects of solar winds.  Lehmann Discontinuity Sediment Sea Lithosphere The Lehmann discontinuity Asthenosphere is abrupt increase of P-wave and S-wave velocitiesand separates the liquid outer Lehmann core from the solid inner Discontinuity core. 6371 km  Density (ρ) of the Earth’s layers Sediment Sea ρ ~ 2.7 g/cm3 ρ ~ 3.3 g/cm3 Lithosphere ρ ~ 3 g/cm3 Asthenosphere ρ ~ 5.5 g/cm3 ρ ~ 9.5 g/cm3 ρ ~ 11.5 g/cm3 The density (ρ) increases from about 2.7 ρ ~ 12 g/cm3 g/cm3 in the upper crust and reaches about 6371 km 12 g/cm3 to the inner core of the Earth.  Behavior of the Earth’s layers Sediment Sea SIMA is the name for the lower layer of the SiAl Earth's crust which is made of rocks rich Rigid in magnesium silicate minerals. Typically when the sima comes to the Lithosphere surface it is basalt and is the lowest layer of the crust. Because the ocean floors are mainly sima, it is also sometimes called the Asthenosphere 'oceanic crust'. The name 'sima' was taken from the first two letters of silica and of magnesium. Rigid/Solid Comparable is the name 'sial' which is the name for the upper layer of the Earth's continental crust, rocks rich in silicates and aluminium minerals. As these elements are less dense than the majority of the earth's Liquid (Ni & Fe) elements, they tend to be concentrated in the upper layer of the crust. Core is rich in nickel (Ni) and iron (Fe) Solid contents. (Fe, Ni & S) 6371 km  Seismic waves through the Earth P Waves 6.0 km/sec S Waves 3.5 km/sec How do we know the structure of the earth? Seismology is the scientific study of earthquakes and the propagation of elastic waves (Primary (P) and Secondary (S) waves) through the Earth’s layers.  6.0 km/sec 2.5 km/sec 3.0 km/sec 3.5 km/sec A seismic wave is a wave that travels through the Earth, often as the result of an earthquake or explosion. Differences in density and other physical properties affect the velocity of seismic waves. Isostasy Isostasy is the state of gravitational equilibrium between Earth's crust and mantle. Balance of adjacent rocks of brittle crust that float on the plastic mantle. For example wood blocks float in water with most of their mass submerged. Crustal blocks “float” on mantle in a similar way. The thicker the block the deeper it extends into the mantle. Oceanic crust (e.g. dominantly basalt) is heavier, denser but less in thickness than the continental crust (e.g. mostly granite). Convection Currents Convection currents are caused by the hot material at the deepest part of the mantle rising, then cooling and sinking again, repeating this cycle over and over. It is like hot water in a pan that has convection currents move in liquid. the When currents the flow in the asthenosphere convecti on move also they the crust. Exercise: Internal Structure of the Earth Exercise: Internal Structure of the Earth 12 1 11 2 10 3 9 4 8 5 7 6  Plate Tectonics You will learn about; - Plate tectonics - Seafloor spreading and continental drift - Minor, minor and micro plates - Sunda Plate -Types of plate boundaries - Distribution of volcanoes and earthquake  What is plate tectonics? Plate tectonics (Greek word meaning pertaining to building) is a scientific theory that describes the large-scale motion of Earth's lithosphere. It builds on the concept of continental drift and seafloor spreading. The Earth’s crust and upper mantle (lithosphere) are broken into sections called plates. Plates move around on top of the mantle like rafts. Pate-tectonic theory was accepted after seafloor spreading was validated in the late 1950s.  Earth’s internal layers: Lithosphere Sea Lithosphere (Crust+ upper Tectonic plates are mantle) Earth's crust piece uppermost and mantle, together sreferred to of as the lithosphere. The plates consist of two principal types of material: oceanic crust (called sima from silicon and magnesium) and continental crust (sial from silicon and aluminium). The lithosphere is the rigid outer part of the earth, consisting of the of crust and a part of the upper mantle. The crust is the outermost solid shell of the Earth.  WHO? Alfred Lothar Wegener 1880-1930 | Berlin, Germany | Meteorologist & Polar researcher | http://www.famousscientists.org/alfred-wegener/ UNIVERSITI MALAYSIA TERENGGANU  WHO THOUGHT OF IT? Wegener’s theory hypothesized that the continents were able to push through the rock of the seafloor to their present position 1960 Scientific discoveries about seafloor spreading combined with earlier theories of continental drift, led to theory of plate tectonics 1950 Theory finally accepted PANGEA - Evidence suggests that the continents were once joined into a single 1915 Fossils from different continents, now far apart, are continent mostly the same. The coastline of Africa & South America look like they are supposed to fit together.  CONTINENTAL DRIFT Permian Triassic 250 mya 200 mya Cretaceous Present day 65 mya 65 mya UNIVERSITI MALAYSIA TERENGGANU FOSSIL EVIDENCE UNIVERSITI MALAYSIA TERENGGANU  EARTH’S MAGNETIC POLES Some minerals have magnetic properties, in molten rock the magnetic properties line up in relation to Earth’s magnetic poles. When the rocks harden, a permanent record of the Earth’s magnetic poles are revealed. Scientists discovered that on each side of the midocean ridges there were magnetic stripes. The stripes showed that at several times in Earth’s history, the magnetic poles have reversed. The stripes matched up on each side of the midocean ridge. This discovery added more evidence to support ocean-floor spreading. UNIVERSITI MALAYSIA TERENGGANU EARTH’S MAGNETIC POLES UNIVERSITI MALAYSIA TERENGGANU  What is continental drift? Continental drift is the movement of the Earth's continents relative to each other, thus appearing to "drift" across the ocean bed. A continent is one of several very large landmasses on Earth. There are up to seven regions commonly regarded as continents. Convection currents in Earth’s mantle drag along tectonic plates.  Seafloor Spreading Seafloor spreading is a process that occurs at mid-ocean ridges, where new oceanic crust is formed through volcanic activity and then gradually moves away from the ridge. Seafloor spreading helps explain continental drift in the theory of plate tectonics. Age of Oceanic Lithosphere  Seafloor spreading: Example Atlantic Ocean Pacific Ocean Transform Faults Indian Ocean  How many major plates are there? Seven major plates (area > 10 million km 2): Pacific North American Plate, Plate, Eurasian Plate, African Plate , Antarctic Plate, Indo- Australian Plate, and South American Plate. North Eurasia American n Plate Plate African Pacific Plate Plate South American Indo- Plate Australia n Plate Antarctic Plate  How many minor plates are there? More than nine minor plates (area 1 million km2 ): Nazca Plate, Philippine Sea Plate, Arabian Plate, Caribbean Plate, Cocos Plate, Caroline Plate, Scotia Plate, Burma Plate, and New Hebrides Plate JDF Plate Caribbean Indian Plate Plate Scotia Plate  How many micro-plates are there? There are about 60 micro-plates (area