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ERTH2415 - Chapter 13, 14, 15.docx

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Carleton University
Earth Sciences
ERTH 2415
Claire Samson

Lecture 13 • Telluric: Electric current induced due to variation in Earth’s magnetic field. • Magnetotelluric sounding measures earth’s magnetic field and curents. • Extreme Variations of the Earth’s magnetic field can have a significant effect on technological systems • What does a magnetometer record? -> Superposition of Internal geomagnetic field and External geomagnetic field. • Differentiation: Denser material gradually migrating to the center of the Earth. • Magnetic poles do not coincide exactly with geographic poles. • Every few years, magnetic poles wander around the geographic poles. • Disturbances affecting technological systems are caused by variations in the external geomagnetic field. • Solar wind: Stream of charged particles flowing away from the Sun’s corono in all directions. • Strong gusts of solar wind are caused by Coronal holes, they occur on small localized areas of the sun’s surface. • They are also caused by Coronal mass ejections. These are Star-scale events, charged particles and radiations released from the sun’s corona. • Magnetic Storm: Temporary large-scale perturbation of the external geomagnetic field due to high solar activity. • They occur at the peak of a solar cycle. • Magnetosphere: Region around the Earth shielded from the solar wind. • Emission of light due to solar winds is Aurora Borealis. • Space weather – is the changing environmental conditions in space. This can be easily be predicted. • Ottawa has an International Space Environment Service. • There are three zones: o Polar Cap o Auroral Zone o Sub-Auroral Zone • Telluric currents affected the blackout in Quebec in 1989 • Lecture 14 • • Silicon and oxygen make up of 75% of the crust. Oxygen being more abundant. • Minerals make up rock. • Mineral: naturally occurring inorganic solid with: o Orderly internal structure o Individual characteristics • Rock: Solid aggregate of one or more minerals. • • Rock Cycle: Process by which older rocks are made into new rocks. • • Igneous rocks: Formed by cooling and solidification from a molten liquid called magma. • Crystallization: Process of mineral formation in a cooling magma. • Cooling at depth: intrusive igneous rocks • Cooling at the surface: extrusive igneous rocks • Magma : partially molten rock below the Earth’s surface. • Lava: Magma that reaches the surface. • Volatiles: gases dissolved in the melt. • Viscosity: Internal resistance of a liquid to flow. High viscosity is higher density. • Higher magma viscosity the more explosive the eruption. • Magma viscosity increases with the percentage of SiO , 2ecreases with temperature, and increases with the amount of solid in the melt. • Volcanism: Process by which magma rise into the crust an
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