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Flashcards in earths structure Deck (57)
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1
Q

why is interstellar space like a vacuum?

A

as it contains very little matter

2
Q

how does the geothermic gradient change?

A

depending on where you are on earth. differences in depth, change in pressure and temperature.

3
Q

what are seismic waves?

A

earthquake waves

4
Q

what is the epicentre?

A

the projection of the focus onto the surface of the earth.

5
Q

what are the 2 types of earthquakes which travel through solid earth?

A

P waves and S waves.

6
Q

what are the differences between P and S waves?

A

P waves are faster than s waves, they are compressional, analogous to sound waves and travel through solid and liquid. s waves (shear), hold the particle motion they don’t occur in liquids, and hence you can tell where liquids are.

7
Q

how can you use seismological evidence for the structure of the earth?

A

if no direct s waves, then there is no liquid in that pathway. you get some diffraction of p and s, and then in the middle- no longer transmits s waves. therefore, there is a liquid outer core.

8
Q

what is the earth made out of in terms of organic materials?

A

oil, protein, fat, rubber, carbon containing material.

9
Q

what is the earth made out of in terms of minerals?

A

solid substances in which atoms are arranged in an orderly pattern.

10
Q

what is the earth made out of in terms of glasses?

A

solid in which atoms aren’t arranged in an orderly pattern. glass forms when a liquid freezes so fast that atoms don’t have time to organise themselves.

11
Q

what is the earth made out of in terms of rocks?

A

aggregates mineral crystals or grains. sedimentary rocks or metamorphic rocks

12
Q

what is the earth made out of in terms of metals?

A

forms when solid material becomes hot and transform into a liquid.

13
Q

what is a sedimentary rock?

A

from from grains that break off pre-existing rocks and become cemented together.

14
Q

what are metamorphic rocks?

A

create when pre-existing rocks undergo changes such as growth of new minerals due to heat change or pressure.

15
Q

what is the earth made out of in terms of melts?

A

form when solid materials become hot and transform into a liquid. molten rock is a type of melt.

16
Q

what are the 4 classes of silicate rock?

A

Felsoc, intermediate, mafic, ultramafic.

17
Q

what are earths 3 distinct types of structures?

A

dry land, oceans and ice covered land.

18
Q

what is topography?

A

variations in elevation.

19
Q

what is earths layered interior?

A

crust (continental and oceanic), mantle (upper, transitional and lower), and core- outer liquid and inner liquid.

20
Q

what is the deepest anyone has drilled?

A

12 km in Russia. this is inly 0.03% of the earth.

21
Q

how do you measure the earths density?

A

find out the earth’s mass, by deflection of an object attached to a surveying instrument. the angle of deflection caused by the gravitational attraction of a mountain indicates the magnitude of gravitational attraction exerted by mountains mass relative to the gravitational attraction of earth mass.

22
Q

what is the continental crust?

A

underlies the continents. thickest is under mountain belt.

23
Q

what is Moho?

A

this is at the base of the continentl crust, which is a difference in density.

24
Q

what is the oceanic crust?

A

this is the crust which is much thinner and underlines the seafloor.

25
Q

what are “ophiolites”?

A

places where slices of the oceanic crust have been incorporated into mountians, and therefore exposed to air

26
Q

what layers do the oceanic crust have?

A

at the top there is a blanket of sediment- clay and tiny shells. beneath this, the crust holds basalt and gabbro.

27
Q

what is the difference in thickness between continental and oceanic crust?

A

continental is 5x thickness of oceanic.

28
Q

what are rifts?

A

plate motions can cause continents to stretch in narrow bands called rifts. the continental crust contains many rock materials.

29
Q

whare are the compositions in the crusts?

A

mafic, felsc in compisiotn, more felsic (granite) composition. oxygen is the most abundant elemnt 93 % of the crust.

30
Q

what is the mantle?

A

the mantle is the largest part of the earth in volume.

31
Q

how thick is the mantle?

A

3000km thick surrounding the core.

32
Q

whar are the 3 sublayers of the mantle?

A

upper mantle, transition zone and lower mantle.

33
Q

what is the mantle made of?

A

almost all solid rock. made up of entirely ultramafic rock- peridotite.

34
Q

why is it not all solid rock in the mantle?

A

so hot, that it is soft enough to flow very slowlu. therfore, mantle can change shape like wax

35
Q

what does the melt in the mantle cause to slow down?

A

causes seismic waves, to slow the melting down.

36
Q

why does convection occur in the mantle?

A

as it is hot and therefore it sinks and coolrock replaces its place.

37
Q

what is the core made out of?

A

iron alloys.

38
Q

why do earthquake waves bend pass the core?

A

cannot pass through the outer part of the core.

39
Q

what are the 2 areas of the core?

A

outer core and inner core

40
Q

what is the outer core made out of?

A

liquid iron alloy, with some iron, nickel, and solicon. its a liquid because the temperature is so high that even at great pressures, its not a solid.

41
Q

what is the inner core made of and why is it solid?

A

solid iron-nickel alloy. even though it is hotter than outer, the inner is solud due to being deoer and even greater pressure. restricts th movement.

42
Q

what is the atmosphere?

A

an envelope of gas.

43
Q

what is the atmosphere made out of?

A

78% nitrogen, 21% oxygen.

44
Q

what is the troposphere?

A

most winds and clouds in the lower level, air undergoes convection.

45
Q

what is the magnetic field?

A

is the region affected by the force emanatating from a magnet. this force grows progressively stronger as you appraoch the magnet (earth)

46
Q

why is the earth a magnet?

A

it is a large dipole, we can draw magnetic field lines. can attarct or repel another magnet and can cause charged particles to move.

47
Q

what is “magnetosphere”?

A

the region inside the magnetic field. without this shoeld, the solar winds would push radiation into the earths atmosphere.

48
Q

what does the solar wind do to the magnetosphere?

A

distorts it, its shaped like a teardrop, and forms a shield aroumd the earth, deflecting the solar wind and protects the earth.

49
Q

what are Van Allen belts?

A

concentrate the plasma coming from the sun. they consist of solar wind particles and cosmic rays nuclei of atoms that have been emitted during supernova explosions. they move so fast that they were able to penetrate the weaker part of the magnetic field. the expand and contract depending on the activities of the sun.

50
Q

how many van allen belts are there?

A

inner proton and electosn. outer- mostly electrons.

51
Q

what causes the northern lights?

A

magnetic field released by spectacular aurorae. some charged particles make it past the van Allen belts, and this causes the northern lights. the ionized atmospheric gases in polar regions cause it to glow.

52
Q

why are there 2 magnetic poles on earth?

A

the stronger the magnet, the greater its magnetisation. north and south, causes a dipole.

53
Q

why are there 2 norths?

A

due to the earths tilt, the planets rotational axis causes the compass to not point true north. the geographical poles of the planet dont coincide with the magnetic poles.

54
Q

what is magnetic inclination?

A

they dont stray more than 15 dgress off true north. the needles angle of tily is called magnetic inclination. the lines tilt at an angle to the surface at mid-latitude.

55
Q

what is basalt?

A

sark-coloured, magnetite-containing igneous rock that forms volanoes,

56
Q

is lava a magnet?

A

cools and solidified. when a volcano erupts, the lava is very hit and thermal energy makes its atoms wobble. each atom acts like a dipole. when this occurs, the magnetic force exerted by one atom cancels the force of another atom, so the lavas a whole isn’t magnetic. however, as the temperature decreases below the boiling point, basalt rock solidifies, as the magnetic crystals begin to form and cool, the dipoles become parallel with the earth’s magnetic field. the dipoles lock position, pointing in the direction of the magnetic pole, and it becomes a permanent magnet.

57
Q

how can you use basalt to predict where the earths magnetic pole was at the time of eruption?

A

the basalt provides a record for the orientation of the earth’s magnetic field lines, as the time which the rock cooled. this is called paleomagnetism.