PG2 - Building a Planet

PG2 - Building a Planet - 9/8/11 Sound has a pitch Pitch...

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Unformatted text preview: 9/8/11 Sound has a pitch Pitch depends on frequency - the number of waves that pass a point in a given period of time Doppler effect 1 9/8/11 High Frequency Low Frequency Color of light is measured by frequency 2 9/8/11 3 9/8/11 Nebular Hypothesis Some data to explain: 1. Planets isolated 2. Orbits ~circular / in ~same plane 3.  Planets (and moons) travel along orbits in same direction… same direction as Sun rotates Molecular cloud 4 9/8/11 Nebular hypothesis The ball at the center grows dense and hot enough for fusion reactions to begin. It becomes the Sun. Dust (solid particles) condenses in the rings. Dust particles collide and stick together, forming planetesimals. 5 9/8/11 Gravity reshapes the proto-Earth into a sphere. The interior of the Earth separates into a core and mantle. original artwork by Gary Hincks Forming the planets from planetesimals: Planetesimals grow by continuous collisions. Gradually, an irregularly shaped proto-Earth develops. The interior heats up and becomes soft. Attendance: A. Please click A B. Please click A C. Please click A D. Please click A 6 9/8/11 What is the probable origin of the sun: A. it formed from the explosion of a star B. it formed from sudden heating of the solar system C. it formed from the inward collapse of a molecular cloud D. it formed during the Big Bang Relative Abundance of Elements 7 9/8/11 Moon formation About 4.5 billion years ago, a Mars-sized body impacted the Earth. Impacter The giant impact propelled a shower of debris into space. Earth 4.2 min. after impact Earth re-formed as a largely molten body… The impact sped up Earth s rotation and tilted Earth s orbital plane 23°. 8.4 min. 125 min. …and the Moon aggregated 8.4 min. 125 min. from the debris. Moon rocks 4.47 billion years old support this impact hypothesis. 8 9/8/11 9 9/8/11 An Early Homogeneous Earth Differentiation Begins 10 9/8/11 1.  2.  3.  4.  Crust Mantle Outer core Inner core The Shallowest Layer of the Earth: the Crust •  The crust is the most heterogeneous layer in the Earth •  The crust is, on average, 33 km thick for continents and 7 km thick beneath oceans; however it varies from just a few km to over 70 km globally. •  The boundary between the crust and the mantle is mostly chemical. The crust and mantle have different compositions. •  This boundary is referred to as the Mohorovičić discontinuity or Moho . •  It was discovered in 1910 by the Croatian seismologist Andrija Mohorovičić. 11 9/8/11 Crustal thickness •  The crust is the most heterogeneous layer in the Earth •  The crust is, on average, 33 km thick for continents and 7 km thick beneath oceans; however it varies from just a few km to over 70 km globally. Middle Earth: The Mantle •  Earth s mantle exists from the bottom of the crust to a depth of 2900 km (radius of 3500 km) – Gutenberg discontinuity •  It is further subdivided into: •  The uppermost mantle (crust to 400 km depth) •  The transition zone (400 – 700 km depth) Beno Gutenberg •  The mid-mantle (700 to ~2650 km depth) •  The lowermost mantle (~2650 – 2891 km depth) •  The rocky mantle is composed mostly of O, Mg, Fe, and Si 12 9/8/11 Earth’s Core   Owing to the great pressure inside the Earth the Earth s core is actually freezing as the Earth gradually cools.   The viscosity of the outer core is   The boundary between the liquid similar to that of water, it flows outer core and the solid inner core kilometers per year occurs at a radius of about 1220 km – Lehman discontinuity, after Inge Lehman from Denmark.   The outer core is the most homogeneous part of the Earth   The boundary between the mantle and outer core is sharp.   The outer core is mostly an alloy of iron and nickel in liquid form.   The change in density across the core-mantle boundary is greater than that at the Earth s surface. Mechanical Layers: 1.  Lithosphere 2.  Asthenosphere 3.  Mesosphere 13 9/8/11 Lithosphere • The lithosphere is the strong uppermost layer of the Earth • There is not a strict boundary between the lithosphere and the asthenosphere as there is between the crust and mantle • It consists of both crust and uppermost mantle • It behaves rigidly, like a solid, over very long time periods Asthenosphere • The asthenosphere exists between depths of 100-300 km • It is the weakest part of the mantle • It is a solid over short time scales, but behaves like a fluid over millions of years • The asthenosphere decouples the lithosphere (tectonic plates) from the rest of the mantle 14 9/8/11 Magnetic Field •  Region affected by Earth s magnet •  Solar wind interacts with magnetic field, distorting it into huge teardrop Shields Earth from solar wind and traps cosmic radiation, protecting Earth from lethal radiation. Magnetic Field Dipole magnet Earth You are here 15 9/8/11 Which layer of Earth is believed to be completely molten: A. crust B. mantle C. outer core D. inner core The object that collided with the Earth to form the Moon was about the size of: A. the dwarf planet Pluto B. the Sun C. the Earth D. the planet Mars 16 9/8/11 Earth's Magnetic Field •  It was first thought that the Earth's magnetic field was caused by a large, permanently magnetized material deep in the Earth's interior •  In 1900, Pierre Curie recognized that permanent magnetism is lost from magnetizable materials at temperatures from 500 to 700°C •  This is known as the Curie point Magnetic Field Nature of Earth s magnetic field W. W. Norton Magnetic field is generated in the outer core 17 9/8/11 Magnetic Inclination Because the Earth s magnetic field is generated deep within the planet, lines of magnetic force run at an angle compared to Earth s surface. At the equator, the magnetic field is completely horizontal At the magnetic poles, the field is entirely vertical At mid-latitudes, the magnetic field is tilted. This angle is called magnetic inclination. Magnetic Declination A compass needle points toward the magnetic north pole rather than true north. Today, the magnetic pole sits ~11° off of the geographic pole The angle between the direction a compass needle points and true north is called the magnetic declination 18 ...
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This note was uploaded on 09/27/2011 for the course GEOGRAPHY 101 taught by Professor Vancura during the Fall '08 term at Rutgers.

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