worksheet 6

Question 1

what happened during the caledonian orogeny

Answer 1

the iapetus ocean closed

Question 2

what happened during the variscan orogeny

Answer 2

the rheic ocean closed

Question 3

what were the principle continents before pangea formed

Answer 3

gondwana, siberia, baltica, laurentia
- avalonia was a microcontinent

Question 4

what were the principle oceans before pangea formed

Answer 4

panthalassic ocean, rheic ocean, iapetus ocean

Question 5

what was in gondwana

Answer 5

present-day south america, africa, antarctica, new zealand, southeastern USA, arabia, southern europe, india

Question 6

what was in siberia

Answer 6

siberia and kazakhstan

Question 7

what was in baltica

Answer 7

scandinavia, eastern russia, north europe

Question 8

what was in laurentia

Answer 8

most of present day north america

Question 9

where was ireland and uk before pangea

Answer 9

southern ireland, england and wales are in avalonia
northern ireland and scotland were part of laurentia

Question 10

what happens during the late cambrian to early silurian period

Answer 10

the iapetus closes (between avalonia and laurentia) and rheic opens

Question 11

when did avalonia form and how

Answer 11

in the cambrian by rifting away from gondwana

Question 12

what is rifting

Answer 12

when crust pulls apart and thins which decompresses the mantle so magma rises

Question 13

how do avalonia and laurentia move during the late cambrian/early silurian

Answer 13

avalonia drifts up from 80S to 35 while laurentia moves east and north. avalonia is moving at a faster rate and catching up with laurentia

Question 14

what happened to the island arc in the iapetus during middle ordovician

Answer 14

it collided with laurentia and oceanic material was over thrusted onto the continental crust. this is part of the grampian phase

Question 15

what happens in the late silurian period

Answer 15

the iapetus ocean closes due to subduction and collision between avalonia, laurentia and baltica

Question 16

what is the acadian phase

Answer 16

the final period of the caledonian orogeny in which the mountain belt is formed between canada –> ireland –> scotland –> greenland –> noway

Question 17

where did subduction occur for the caledonia orogeny

Answer 17

oceanic crust subducted towards the north in the oceanic trench on the northern laurentian margin

Question 18

what type of collision was the one between avalonia and laurentia

Answer 18

bleak, non head on collision. there was some sliding past one another

Question 19

what is geological evidence of the avalonian and laurentian blocks colliding in ireland

Answer 19

distinction sections of precambrian rocks align with laurentian margin in the north and avalonian margin in the south

Question 20

what is an accretionary wedge/prism? where can they be found?

Answer 20

deformed sediments created as iapetus seafloor sediments were scraped off the oceanic crust during subduction. the younger sediments are further south of the laurentian margin

Question 21

what accompanied the closure of the iapetus and how old are the rocks

Answer 21

granite emplacement which is 360-480 myo (from late devonian to early ordovician)

Question 22

what happened to the mountains that were created by the caledonia orogeny and what did they form

Answer 22

they were eroded and weathered down which formed an angular unconformity

Question 23

how did the continents move to close the rheic

Answer 23

gondwana drifted northwards to form with the laurentia-avalonia-baltica continent

Question 24

when was the rheic closed

Answer 24

by the late devonian (360-380 mya)

Question 25

what was the last step of all of the continents combining? what is the evidence for this?

Answer 25

baltica came together with siberia (the ural mountains were formed as baltica collided with kazakhstan during caroniferous)

Question 26

when was pangea formed by

Answer 26

335 mya

Question 27

what are the appalachian mountains proof of

Answer 27

the rheic ocean closing