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Science > Plate Tectonics > Flashcards

Plate Tectonics Flashcards

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0
Q

Magnetic striping

A

Patterns of magnetism preserved in rock on each side of ocean ridge

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1
Q

Continental drift

A

Separating of continents by drifting across the oceans

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2
Q

Plate Tectonics

A

Theory that earth’s crust is cracked into many large pieces ( tectonic plates) that move on asthenosphere

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3
Q

Rifting

A

Process of continents breaking up, subsiding and allowing in the sea

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4
Q

Seafloor spreading

A

Process of new crust forming at ocean ridges & spreading outwards

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5
Q

Island arc

A

Chain of Islands formed at edges oceanic and oceanic plate boundaries where one subducts

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6
Q

Earthquake

A

Rapid movement of ground, usually up & down & back & forth in a wave motion

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7
Q

Seismic wave

A

The shaking, wave like movement that travels though Earth

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8
Q

Surface wave

A

Seismic wave travels along surface of Earth in crust

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9
Q

Observations that led to hypothesis of sea floor spreading

A

Discovery of the global rift system (cracks in middle of ridges) and ocean ridges

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10
Q

Subduction

A

Crust sinking under another plate = trenches, volcanic arc (on land) Island arc (chain of Islands)

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11
Q

Evidence of continental drift

A

Jigsaw puzzle, fossils of same species found on continents far apart, glacial sediments in places where don’t exist now, glacial scratches line up

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12
Q

How Wegener deduced what Pangaea looked like?

A

Rearranged continents- join, fit like puzzle & distribution of fossils was continuous across land masses

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13
Q

Hess’s theory of Seafloor spreading

A

Proposed new crust formed at ocean ridges & spreading outwards - crust sinking down into earth in ocean trenches = subduction

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14
Q

3 types of evidence that supports sea floor spreading

A

Magnetic striping- rocks at particular distance on both sides of mid ocean ridge had same magnetic direction

Older rocks further away from ridges

Sedimentary layers thicker as move away from ridges

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15
Q

Why Africa and America older than Seafloor of Atlantic

A

New Seafloor constantly created & destroyed while continents remain at surface, moving around on the plates

16
Q

Explain process of magnetic striping

A

Coloured areas represent rock formed when mag field was same as today, grey = when reversed
Magnetic minerals in rocks line up in like compass & point north as magma cools.
Layers symmetrical on both sides of axis coz magma separates away on both sides =ly as cooling

17
Q

How convention & heat involved in movement of plates

A

Rocks of asthenosphere very hot & viscous. Heat creates convention cells in mantle with warm rock pushed ^ & cooler rock sinking down. As rock ^ & flow sideways beneath crust, plates dragged by friction

18
Q

Compare theories of CD & PT

A

Both proposed continents moved
CD - no mechanism or evidence
Plate tectonics- proposed crust cracked into large pieces called TP, subduction & Seafloor spreading explained movement

19
Q

Distinguish between mag striping & mag reversal

A

Mag striping- bands of alternating mag field that symmetrical on both side of ridge
Mag reversal- where mag field reveres & N becomes S - preserved in rocks

20
Q

How Red Sea formed

A

Rifting when 2 plates separated, subsides & allowed sea from N & S, flooded Rift Valley

21
Q

Why geologist believe Aus moving N if there’s ocean trench Aus & indo & ridge between Aus & Antarctica

A

New crust forms forms S of Aus & pushed plate northwards where it subducts under indo

22
Q

Evolution of flora & fauna by change in environmental conditions following break up of Gondwana

A

Aus separated from Antarctica 40 MYO - allowed cold current to cool Antarctica & lock up moisture that fell as rain in Aus. S Aus become drier, drifting ^ , become more arid as it entered tropical region –> flora that was adapted to dry conditions

23
Q

Indian plate & Eurasian plate collide

A

Both light crust, same densities, pushed upwards = fold mountains

24
Q

Fossils found on Mt Everest

A

Seafloor sedi rocks from Indian plate uplifted

25
Q

Why Aus became drier

A

Movement of plates allowed formation of cold current & this locked lots of moisture in Antarctica- reduced rainfall in S Aus. Warm currents formed & temp rose as ^ into topics & rainfall declined

26
Q

Why quakes and volcanoes mainly found near plate boundaries

A

Place where earth moves most , expected to have most severe quakes, most E generated for earth movement, volcanoes occur at PB where magma can reach surface through weaknesses by plate movement - subduction generates heat

27
Q

Damper

A

Structures that move in opposition to seismic waves & appose their affect

28
Q

Base isolation

A

Pads, springs & bearings that allow building to suppress waves by moving rather than vibrating

29
Q

Island chains

A

Form over hotspot as plate keeps moving & new volcanoes form one after other. Only one active,
island arc = chain of volcanoes, usually all active

30
Q

Magma from C & O and from O& O

A

C plate have more silica in them, makes magma viscous

O & O- rocks with lots of water create steam during subduction, magma not as viscous, lack of silica

31
Q

Process of Seafloor spreading & subduction & how tees relate to convection

A

New crust formed at ocean ridges & spreading outwards, eventually results in ocean floor converging with nearby plates & subduction. Both driven by convection currents in mantle

32
Q

Plate tectonics and discuss it’s past impact on ocean currents and climate on of earth

A

Ocean currents affected by plate movement eg; Antarctic circumpolar current when Aus separated- cooled Antarctica greatly, formed ice sheets
Warm currents on east of Aus block from getting to Antarctica

33
Q

Difference in ocean & continental crust

A

O- dark, dense & low in silica & lighter elements eg: Al

C - light colour, less dense due to high silica content

34
Q

Compare subduction of O& O and C& O

A

Both cases one plate subducts, forming trench & volcanic activity occurs
2 O = island arc
C & O = one land, fold mountains

35
Q

How mountains can form

A

Collision of C&C, O&C, transform boundaries, diverging boundaries have mountains by volcanic activity, island arcs mountains in sea, hotspots

36
Q

seismograph, seismometer,

A

Measures and records details of earthquakes, eg: force & duration

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