• 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
• 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
• Solar wind: Stream of charged particles flowing away from the Sun’s corono in all
• 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
• 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
• 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