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EARTH & SPACE SCIENCE

EARTH & SPACE SCIENCE. Chapter 2 Earth as a System 2.1 Earth: A Unique Planet. 2.1 Earth: A Unique Planet Objectives. Describe the size and shape of Earth. Describe the compositional and structural layers of Earth’s interior. Identify the possible source of Earth’s magnetic field.

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EARTH & SPACE SCIENCE

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  1. EARTH & SPACE SCIENCE Chapter 2 Earth as a System 2.1 Earth: A Unique Planet

  2. 2.1 Earth: A Unique Planet Objectives • Describe the size and shape of Earth. • Describe the compositional and structural layers of Earth’s interior. • Identify the possible source of Earth’s magnetic field. • Summarize Newton’s laws of gravitation.

  3. Introduction • Earth, the third planet from the Sun, is the only planet to have liquid water on the surface and posses an atmosphere with a large percentage of oxygen. • Earth is the only planet known to support life. • Scientists study the Earth so that they can better understand the conditions necessary for life and look for those conditions elsewhere in the universe.

  4. Earth Basics • Our 4.6 billion year old planet is mostly rock, but about 70% of its surface is covered by a global ocean. • Earth is an oblate spheroid, meaning that it is slighlty wider at the equator and slightly compressed from pole to pole.

  5. Earth Basics • The oblate spheroid shape is due to Earth spinning on its axis. • Pole-to-pole circumference = 40,007 km • Equatorial circumference = 40,074 km • The difference in elevation of the highest mountain down to the deepest ocean trench is only about 20 km. • Earth’s average diameter is about 12, 756 km.

  6. Earth’s Interior • Since direct observation of Earth structure is limited to the upper few kilometers, indirect methods are needed for greater depths. • The study of seismic waves (vibrations that travel through Earth) has helped scientists to identify three major compositional zones and five major structural zones.

  7. Earth’s Interior • Compositional Zones • Crust • Mantle • Core • Structural Zones • Lithosphere • Asthenosphere • Mesosphere • Outer core • Inner core

  8. Earth’s Interior • The crust is the solid, thin, outermost layer of Earth and only makes up about 1% of the mass of Earth. • Oceanic crust is only 5 to 10 km thick and lies beneath the ocean. • Continental crust, less dense than oceanic crust, varies from 15 to 80 km thick. • The lower boundary of the crust is called the Mohorovičić discontinuity (or Moho).

  9. Earth’s Interior • The mantle, denser than the crust, is nearly 2,900 km thick and makes up about two-thirds of Earth’s mass. • The core has a radius of about 3,500 km and is composed of mostly nickel and iron. • The cool, brittle part of the uppermost mantle and crust make up the lithosphere that can be between 15 and 300 km thick. • The asthenosphere, which is about 200 km thick, has the ability to flow (plasticity). • The solid mantle rock between the core and the asthenosphere is called the mesosphere.

  10. Earth’s Interior • The depth of the boundary between the mantle and the outer core is about 2,900 km. • The outer core (from 2,900 km to 5,150 km) is thought to be liquid. • The inner core is presumed to be a dense, rigid solid. • Collectively, the core makes up about one-third of the Earth’s mass.

  11. Earth as a Magnet • The magnetosphere is the region affected by the Earth’s magnetic lines of force that extend from the south geomagnetic pole to the north geomagnetic pole. • It is thought that motions in the liquid core generate the currents that produce the Earth’s magnetic field. • The sun and the moon also have magnetic fields, which does not support the idea that the Earth’s magnetic field is generated by the motion of the nickel-iron outer liquid core movement.

  12. Earth’s Gravity • Gravity is the force of attraction that exists between all matter in the universe. • Newton’s law of gravitation states that the force of attraction between any two objects depends on the mass of the objects and the distance between the objects. • The more massive the objects and the closer the objects, the greater the force of attraction. • Objects are pulled toward the center of the Earth due to Earth’s gravitational force.

  13. Earth’s Gravity • Mass is the amount of matter that makes up an object. • Weight is a measurement of the force of gravity exerted on an object. • The newton (N) is the SI unit of measurement for weight (1 kg on Earth is about 10 N). • An object’s weight depend on its mass and its distance from the center of Earth. • Your weight at the equator would be about 0.3% less than your weight at the North Pole.

  14. References • Earth - http://www.calpoly.edu/~rechols/F03astrox103lab1.html • Earth’s Compositional Zones - http://nsm1.nsm.iup.edu/hovan/classes/geos103_outline.html • Earth’s Structural Zones - http://www.astro.virginia.edu/class/oconnell/astr121/im?C=D%3BO=A • Mohorovičić Discontinuity - http://pbisotopes.ess.sunysb.edu/classes/oldclasses/Geo310/9-28/mohorovicic_discontinuity.htm

  15. References • Andrija Mohorovičić - http://mahazu.hazu.hr/ENG/ind-eng.html • Earth’s Magnetic Field - http://www.calstatela.edu/faculty/acolvil/plates.html • Law of Universal Gravitation - http://www.csulb.edu/~rtoossi/engr370i/2.htm • Effect of Mass and Distance on Gravity - http://www.glenbrook.k12.il.us/gbssci/phys/Class/circles/u6l3c.html

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