Key terms Final Flashcards
What are telluric currents?
Variations in the earths magnetic field that induce electrical (telluric) currents.
A current in the ground or on electrically conducting networks
What is a synonym for the earth’s magnetic field?
geomagnetic field
What is a geomagnetic hazard
Extreme variations of the earth’s magnetic field can have a significant impact on technological systems
What is the earth’s internal geomagnetic field?
earth’s core
What is the external geomagnetic field?
Ionosphere and magnetosphere
What type of variations does the internal geomagnetic field have?
Slow variations
What are disturbances affecting technological systems caused by?
Disturbances affecting technological systems are caused by variations of the external geomagnetic field. Short duration (hours,days) and driven by solar activity
What is solar wind?
stream of charged particles flowing away from the sun’s corona
What are coronal hole explosions?
Occur in small localized area of the sun’s surface. Violent explosions of heat up material and shoot it in outer space.
What are coronal mass ejections?
Star scale events. Charged particles and radiation are released from the sun’s Corona in the vicinity of sunspots
What is a magnetic storm?
Temporary ( a few hours to a few days) large scale perturbation of the external geomagnetic field due to strong gusts of solar wind
What is earth’s magnetosphere?
Region around the earth shielded from the solar wind by the internal geomagnetic field
What is the interaction between the solar wind and the earth’s magnetosphere?
Charged particles from the solar wind create currents in the ionosphere, Ionospheric currents and electromagnetic induction cause variations in the external geomagnetic field and then more electromagnetic induction induce telluric currents
What is space weather?
Changing conditions in space related to solar activity
What is a meteoroid?
Extraterrestrial debris orbiting the sun
What is the primary source of extraterrestrial debris?
Most meteoroids are asteroids or fragments from asteroids
What is an asteroid?
Small rocky body orbiting the sun. Asteroid < planet
What level of hazard do asteroids from the main belt pose for earth?
relatively low impact hazard to earth
What level of risk do near earth asteroids pose?
near earth asteroids pose a higher impact hazard than main belt asteroids
What are the two types of near earth asteroids?
Apollo asteroids which cross earth’s orbit and Aten asteroids which also cross earth’s orbit)
What is a secondary source of extraterrestrial debris?
A few meteroids are fragments from comets
What is a comet?
Small object composed of ice and rock debris moving through outer space
Where are comets in relation to the sun?
Very far away from the sun. Comets: stable water ice, material dispersed too thinly for planet formation
Did Swift tuttle comet cross earth’s orbit?
It did, in an 133 year round trip
What are impactors?
Most impactors are near earth asteroids or fragments of asteroids
What is cosmic dust?
Pass through the atmosphere unchanged and settles on the surface of the earth (0.001-1mm). Amounts to ≈ 10 to the power of 5-10 to the power of 6 kg/day (planet earth is gaining weight)
What are shooting stars?
Earth is protected by its atmosphere. Shooting stars melt in the atmosphere because of friction. They blaze during ~1 second, 100 km above ground, we see the streak of hot air (approx 1mm)
What are meteorites?
Pass through the atmosphere and fall on the earth’s surface. Might split into midair fragments. During entry, exterior melts and is stripped away (Cools while reaching the surface, Often covered by black, glazed crust, Sometimes thumb-print texture due to atmospheric turbulence)
What are the two different definitions of a meteorite?
1) meteoroid between 1mm and 100m in diameter
2) impactor that has hit the ground (meteorite)
What are asteroids
diameter > 100m. Not slowed down by the atmosphere and explode on contact with earth’s surface
What are the two definitions of asteroids
1) small rocky body orbiting the sun
2) impactor larger than 100m in diameter
What was important about Chelyabinsk, Siberia?
Massive firebal in the sky and impact. Powerful shock wave (1500 people injured mostly from shattered glass
What was important about Tunguska, Siberia?
No crater
How old is planet earth?
4.6 billion years (Ga)
What is the time unit used in geology?
1 million year (Ma)
What is important to know about the K/Pg boundary event?
Impact of global consequences (extinction) related to this impact
What is one of the causes of the extinction from the K/Pg event?
Stress on life from extensive volcanism in Decca
What scale is used to evaluate impact hazard?
The torino impact hazard scale
What is the typical diameter of a crater?
Crater diameter ~ 20x impactor diameter. Craters with diameter > 5km do not contain meteorites
What are some distinctive features of impact craters?
1) circular feature
2) crater is steep sided and closed
3) rim rocks are titled away from the crater
4) shattered rocks on the crater floor
5. large angular blocks of rock scattered around crater
6) presence of meteorite fragments
7) shock minerals (indicative of extreme T and pressure)
8) shatter cones
9) melted rock due to impact
What is a shatter cone?
A conical fragment of host rock fractured by the shock wave generated by the impact
Core features of Simple vs. Complex crater
Simple crater: Small impactor, diameter < 5km
Complex crater: large impactor, diameter > 5km
What is the most important way that gravity varies at different locations on the surface of the earth?
Heterogeneities in the subsurface
What is the instrument used to make gravity measurements in the field called?
a gravimeter
What is mass movement?
Collective name for a variety of processes for the downslope movement of earth materials under the direct influence of gravity
What is the driving force?
is the component of gravity parallel to the slope
What is the resisting force?
is proportional to inertia and friction and counteracts the driving force
What is friction?
force that resists motion between two surfaces in contact
What are the controlling factors of friction?
Surface roughness of the surfaces and presence of lubricants
What are the friction coefficients
mu=0.3, brick on moist clay is less stable
mu=0.5 brick on dry clay
mu=0.6 granite on granite more stable
What is Congelifraction?
Disintegration of a rock due to several cycles of water freezing and melting
What percentage do silicon and oxygen account for in the crust?
~75%
What is a silicate?
Group of minerals containing Si and O combined with other elements. Most abundant mineral group in the earth’s crust
What is clay?
General term which describe a variety of complex sheet silicates. Structure is a stack of thin sheets, sheet surface is negatively charged. Attracts water molecules and positively charged ions
Water is a bipolar molecule with a positive and negative side, describe positive and negative side
Positive side of water molecules attracted by negative charges on the surface of clay sheets
What binds the clay in a flocculated structure?
Salt binds the clay sheets and silt together
What type of rocks do mass movements occur in most frequently?
They occur in all three types but most often in sedimentary rocks
What are the particle sizes or rock, debris and earth?
Rock is the largest, then debris (coarse soil particles) and then earth (fine soil particles)
What are falls?
Rapid, free-fall mass movement. A bouncing rolling end over end motion. Fragments ranging in size from small grains to large blocks. They develop in material weakened by fractures
What is a slide?
Mass movement involving motion along a failure surface. Material remains as a block (preslide coherence maintained) and failure surface is well defined
What are lateral spreads?
Special case of translational slide in which movement of earth material results from liquefaction of subjacent material. Related to distinct geological conditions present in northern environments
What is liquefaction?
Phenomenon in which the strength of soil is reduced by rapid and violent shaking or loading. Occurs in saturated soils in which the space between particles is filled with water.