The Interior of the Earth Bagunas, Steffi Monica Codina, Marvin Lucero, Marriel C. Sibi, Anthony Leigh
Structure of the Earth The Earth is formed of three concentric layers: • Crust • Mantle • Core
Earth’s Crust • The outermost layer of the earth • 40 km (25 miles) thick in average making it the thinnest of the Earth’s layer • Contains all known life of the Earth Earth’s crust is divided into two types: • Continental Crust • Oceanic Crust
Continental Crust • The relatively thick part of the earth’s crust which is 42 km thick that forms the large landmasses. • Composed mainly of sedimentary, metamorphic, and igneous rocks and granitic and basaltic layer. • It is generally older and more complex than the oceanic crust. • 40% of earth’s surface is now underlain by continental crust including mountain ranges and volcanoes.
Oceanic Crust • The relatively thin part of the earth’s crust that underlies the ocean basins which is 8 km thick. • Oceanic crust is heavier than continental crust. • Subduction=The heavy oceanic crust is constantly sinking, very slowly, underneath the lighter continental crust. • Volcanic arc=A chain of volcanoes formed at a subduction zone. • Earth enjoys a brand-new oceanic crust once every 200 million years or so.
Earth’s Mantle • It lies between the core and the crust. • A gooey, hot layer of magma and other semi-solid rocks and minerals. • About 2,900 kilometers (1,802 miles) thick. • Largest layer of the earth • The movement of the mantle is the reason that the plates of the Earth move • The temperature of the mantle varies from 1600 degrees Fahrenheit at the top to about 4000 degrees Fahrenheit near the bottom Layers of the mantle: • Lithosphere • The thin outermost shell of the upper mantle . • Cooler and more rigid. • Together with the crust, this layer is called the Earth’s lithosphere. • The lithosphere is actually broken up into several large pieces, or plates.
Asthenosphere • The plates of the lithosphere “float” on a softer mantle layer called the asthenosphere. • Their very slow motion is the cause of plate tectonics. 3. Upper mantle • Lies below the asthenosphere • Stronger and more solid than the asthenosphere. • All layers below the crust down to a depth of about 670 kilometers (416 miles) are known as the upper mantle. 4. Lower mantle • Lies between the upper mantle and the core is known as the lower mantle. • It is denser and hotter than the upper mantle.
Earth’s Core • The very hot surface of the earth • It is made almost entirely of metal. • It is a ball of metal which makes the entire planet magnetic and controls the Magnetic field. The core is made of two layers: • Outer Core • Inner Core Outer Core • Borders the mantle and the inner core • Shaped like a ball • The outer core is made mostly of iron and nickel which form an alloy, or a mixture of metallic elements. • The outer core is approximately 2,300 km (1,430 miles) thick. • The alloy of the outer core is very hot, between 4,000 and 5,000 degrees Celsius (7,200 and 9,000 degrees Fahrenheit).
Inner Core • The inner core is made mostly of iron. • It is approximately 1,200 km (750 miles) thick. • The iron is here extremely hot—between 5,000 and 7,000 degrees Celsius (9,000 and 13,000 degrees Fahrenheit) • The inner core is mostly solid and rotates faster.
Earth's magnetic field (also known as the geomagnetic field) is the magnetic field that extends from the Earth's interior to where it meets the solar wind, a stream of charged particles emanating from the Sun. Earth’s Magnetism
Importance • The magnetic field of the Earth deflects most of the solar wind. The charged particles in the solar wind would strip away the ozone layer, which protects the Earth from harmful ultraviolet rays. One stripping mechanism is for gas to be caught in bubbles of magnetic field, which are ripped off by solar winds. Calculations of the loss of carbon dioxide from the atmosphere of Mars, resulting from scavenging of ions by the solar wind, indicate that the dissipation of the magnetic field of Mars caused a near-total loss of its atmosphere.
So how did the Earth get its magnetic field? • Magnetic fields surround electric currents, so we surmise that circulating electic currents in the Earth's molten metalic core are the origin of the magnetic field. A current loop gives a field similar to that of the earth. The magnetic field magnitude measured at the surface of the Earth is about half a Gauss and dips toward the Earth in the northern hemisphere.
Magnetoshpere • A magnetosphere is the area of space near an astronomical object in which charged particles are controlled by that object's magnetic field. Near the surface of the object, the magnetic field lines resemble those of a magnetic dipole. Farther away from the surface, the field lines are significantly distorted by electric currents flowing in the plasma (e.g. in ionosphere or solar wind).When speaking about Earth, magnetosphere is typically used to refer to the outer layer of the ionosphere, although some sources consider the ionosphere and magnetosphere to be separate.
DYNAMO THEORY? • In geophysics, the dynamo theory proposes a mechanism[which?] by which a celestial body such as Earth or a star generates a magnetic field. The dynamo theory describes the process through which a rotating, convecting, and electrically conducting fluid can maintain a magnetic field over astronomical time scales. • Walter M. Elsasser, considered a "father" of the presently accepted dynamo theory as an explanation of the Earth's magnetism, proposed that this magnetic field resulted from electric currents induced in the fluid outer core of the Earth. He revealed the history of the Earth's magnetic field through pioneering the study of the magnetic orientation of minerals in rocks. • In order to maintain the magnetic field against ohmic decay (which would occur for the dipole field in 20,000 years), the outer core must be convecting. The convection is likely some combination of thermal and compositional convection. The mantle controls the rate at which heat is extracted from the core. Heat sources include gravitational energy released by the compression of the core. • Dynamo theory describes the process through which a rotating, convecting, and electrically conducting fluid acts to maintain a magnetic field. This theory is used to explain the presence of anomalously long-lived magnetic fields in astrophysical bodies.
Earth's Magnetism Gilbert’s Experiment Permanent Magnet Fossil Magnet/ Paleomagnetism
-pioneer in the modern study of magnetism and electricity He wrote : De Magnete, MagneticisqueCorporibus, et de MagnoMagneteTellure(Concerning Magnetism, Magnetic Bodies, and the Great Magnet Earth), in 1600 William Gilbert
William Gilbert Gilbert coined the term electrics He also invented the term magnetic pole the first man to research the properties of the lodestone (magnetic iron ore). The unit of measure of magnetomotive force is called the gilbert, in his honor.
Types of Magnets Types of magnetic Materials Permanent Induced electromagnet Ferromagnetism Paramagnetism Diamagentic
magnetic elements The big three : Iron(Fe), Nickel(Ni), Cobalt (Co) The earth is a magnet, geomagnetism, poles: north seeking and south seeking rule of action: opposite poles attract, like poles repel
Gilbert’s Experiment : Induced Magnetism When a piece of unmagnetised magnetic material touches or is brought near to the pole of a permanent magnet, it becomes a magnet itself. The magnetism is induced.
Earth’s Magnetism The Permanent Magnet
permanent magnet a material that is magnetized and creates its own persistent magnetic field strength depends upon the material used in its creation If it loses its magnetic properties, as it does by heating to a (maximum) temperature, it will be rendered useless and its magnetic properties can be only recovered by re-magnetizing
Earth’s Magnetism Magnetic Reversals, Magnetic Anomalies Fossil Magnet / Paleomagnetism
Magnetic Reversals North pole magnetic line of forces and the South pole magnetic line of forces exchange positions.
Normal Polarity Magnetic lines of forces leave the earth and goes near the geographic North Pole It is the same as the present polarity.
Reversed Polarity Magnetic lines of forces run the other way leaving the earth near the North Pole and enters the earth near the South Pole.
Paleomagnetism the study of the record of the Earth’s Magnetic Field in rocks, clay, or bricks Fossil Magnetism retained in certain rocks possible because iron-bearing minerals such as magnetite may record past directions of the Earth's magnetic field.
Magnetic Anomaly Caused by the circulation patterns in the Earth’s core Positive Anomaly – develops over a rock that is more magnetic than neighboring rock Negative Anomaly – indicates rock with low magnetism
Tectonic plates = actually slide around on the mantle causing earthquakes, mountain formation, continental drift, volcanoes, and other geological activity on the crust.
Continental Drift and Plate Tectonics From the time maps of the globe became available, people wondered about the arrangement of the continents and oceans. Hundreds of years later, valid explanations were constructed.
Early Observations Leonardo da Vinci and Francis Bacon wondered about the possibility of the American and African continents having broken apart, based on their shapes. This thinking continued up into the early 20th century, to a meteorologist named Alfred Wegener.
Pangaea Wegener revived the early idea of continental drift, contending that all of the present-day continents were connected, side-by-side, as long ago as the Carboniferous (~300 Myr). He called the supercontinental mass Pangaea, Greek for ‘all lands’.
Wegener’s Evidence Wegener’s summary was based on a number of careful observations: -- matching rock, fossil, glacier, and structural relations among different parts of different continents
Continental Drift: Fossil Evidence Mesosaurus: purely freshwater reptile Glossopteris: seeds too large to be effectively wind-transported
Continental Drift: Glacial Evidence Large ice masses carve grooves in the rocks over which flow. Such masses tend to flow outward (generally downhill) from a central locality.
Continental Drift: Rock Ages Even before geochronology, the relative framework of rock ages showed strong correlation across the Atlantic, as did mountain ranges of similar age.
Wegener never lived to see the general acceptance of continental drift, largely because of the lack of a mechanism. Wegener considered the buoyant continents to be ‘plowing’ through the mantle, resulting in mountain belts on continental edges. Mechanism of Continental Drift?
Beginning just after Wegener’s end, Arthur Holmes began to describe mantle heat flow in terms of convection. Mantle Convection Deep materials, hotter than their surroundings (and hence buoyant), would tend to flow upward. In approaching the cool surface of the Earth, the material would lose its thermal energy, cool and sink, having lost buoyancy. The motion of mantle material put into action by convection thus becomes a plausible mechanism for moving rigid pieces of the crust over some more actively flowing mantle material.
Materials that can flow tend to lose thermal energy by the convection process. This explains circulation in a pot of water that is being heated from below in the same way it describes the cooling of the Earth. Mantle Convection
Earths crust is divided into 15 major tectonic plates: • North American • Caribbean • South American • Scotia • Antarctic • Eurasian • Arabian • African • Indian • Philippine • Australian, • Pacific • Juan de Fuca • Cocos • Nazca plates.