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Chapter 16.1.docx

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GOPH 375
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Chapter 16 Extraterrestrial Causes  “Space weather” changing environmental conditions in space due to varying solar activity. Organizations like CSWFC forecast geomagnetic activity in polar cap/auroral/sub-auroral zones  Solar wind: stream of subatomic particles from the sun. Hot fringes released can’t be restrained by gravity and are sent in all directions. Strong gusts caused by coronal holes (localized, fast plasma) and coronal mass ejections (star-scale, clouds of plasma released in sunspots)  Figure 16.3 sunspot cycle – number of sunspots. telluric currents in surface of Earth o Telluric electrical current propagating in the Earth or through the sea  Electromagnetic induction: magnetic field variations induce electrical currents in a medium, and induced currents generate their own magnetic field. Always currents flowing through rocks  Magnetic Storms: electric currents are produced in the ionosphere in response to solar wind disturbances, causing geomagnetic variations. Lasts 24-48 hours, electric currents are called telluric currents are induced on earth’s surface and conducted/affect power, telephone and pipelines. Common near the peak and decline of the sunspot cycle  Engineering pipelines – know example caused by galvanic erosion. Design your pipeline so the current flows the other way, so your pipeline doesn’t erode. Common to impress a constant negative voltage on pipelines to prevent corrosion from telluric currents. Reduce power on transmission lines when a magnetic storm warning is in effect o 1989 Hydro-Quebec Power Blackout: coronal mass ejection particles triggered a magnetic storm through power transmission lines and hydroelectric dams.  Space weather effects on technological systems: failures caused by bombardment of charged particles, disturbances of the ionosphere, and electromagnetic induction effects  Solar winds travel at 500 m/s in ionosphere and cause damage to circuits, satellites, radio (communication) transmissions, . GPS rarely affected because they’re at a higher frequency  Geomagnetic activity and technical problems first discovered with the telegraph  Impact Scars aka astroblemes made by collision from space debris o Moon used to be bombarded a lot, now little activity. Maria – flood basalts poured on the moon. Impact scars still evident on the moon because it is geologically dead (no life), o Earth is dynamic, most impact scars are hidden by tectonic/glacier movements, erosion, buried by sediment, sea, or flood basalt  Solar system formation – 4.571 Billion years ago Extraterrestrial debris  Asteroids – rocky bodies left over between mars and Jupiter. Their average impact velocity is approx 20 km/sec. Icy masses found in between 4 inner and 4 outer planets (asteroid belt) orbit the sun o 3 largest: Ceres, Pallas, Vesta – Asteroids can have moons o Pull of Jupiter stops asteroids from forming a planet o Gaps within asteroid belt align with orbit time of Jupiter. If an asteroid is knocked into the gap, it’ll likely hit a planet o Some asteroids are solids, some are 2+ similar sized bodies bound together by gravitational attraction. Less energy needed to break an asteroid than to scatter its fragments, so an asteroid could be broken but pieces would remain together in a rubble pile o 3 groups of asteroids have orbits that intercept that of earth/mars and thus, collide often: Apollo, Aten, and Amor  Comets: surprisingly small o Kuiper belt: flattened disk of short-period comets - average impact approx 28 km/sec. K comets are debris from icy planet formation; bodies that never collided and accelerated into a planet  Short comets will die by erosion or collision with the sun  Swift-Turtle comet has been seen on many of its orbits, will hit earth/moon eventually. Most popular is Halley’s comet o Oort cloud (average impact approx 57 km/sec to 72-73 km/sec). This is the maximum velocity impact on Earth. Contain ice and rock  Long period comets – orbits take them far beyond our solar system/planets  Can enter our solar system at any time/angle and hit earth  Perihelion (end of comet orbit) aphelion (end of comet journey)  Luminous tail of a comet occurs when it gets close to the sun and the ice subliminates to form gas/vapor that trails behind. When all ice is gone, inner rocky core is like an asteroid  Meteoroids – pieces of asteroids/comets that orbit the sun  Cosmic dust – tiny meteoroids so small they pass through the atmosphere unchanged and settle as rain  Meteors – meteoroids that blaze
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