Easter Flashcards
(34 cards)
What is the Caledonian orogeny associated to?
The closure of the Iapetus ocean
Scotland and England colliding
Grampian, Scandian, Acadian
What is a terrane?
An area bounded by a fault with distinct features and geological history
What is the hinterland and the foreland?
Hinterland- land near a deformation front
Foreland- land far away from a deformation front
What is type locality?
Internationally agreed location where the boundary between 2 periods can be seen.
Based of fossil assemblages, such as graptolites in Dob’s Lin, Scotland
What are the 5 main sutures in Scotland?
Moine Thrust
Great Glen Fault
Highland Boundary Fault
Southern Uplands Fault
Iapetus Suture
What are the 3 main orogenies and when did they occur?
Cadomian (Neoproterozoic- Cambrian)
Caledonian (Ordovician- Devonian)
Variscan (Carboniferous)
What are glaciations and evidence for them?
When ice isn’t only found at the poles
E.g. Quaternary glacial and interglacial cycles
Evidence are dropstones, boulder clay at Ketton Quarry found at the end of a glacier when it melts
How can past temperatures be determined?
Oxygen isotopes O18/O16
Look at foraminifera, greater means less O16 so more ice= colder temps
How does atmospheric CO2 correlate with length of subducting zones?
More subducting zones more CO2 in the atmosphere, this is due to volcanic gassing
So more CO2 is released, and may also be correlated with temp as it can act as a greenhouse gas
What is the difference between eustatic and isostatic?
Eustatic changes worldwide, in sea level
Isostatic local changes in topography due to uplift
What is extensional subduction?
Cold dense oceanic lithosphere subducting
Leads to slab roll back
Leads to extensional basin
What is contractional subduction?
Warm oceanic lithosphere subducts
Subducts as a flat slab, which can be detected by using seismography
Causes orogenic shortening
What is the arc-continental collision?
Causes flipping of subduction direction
e.g. Taiwan
What is continental- continental collision?
Causes the formation fold mountains
Plates are thrust up
e.g. Himalayas
What are the key points in the history of UK?
550Ma- Iapetus subducting beneath Gondwana, passive margin
490Ma- Iapetus subducting under, however no longer passive
470Ma- Taconic arc and Laurentia, Arc-continent collision
440Ma- Avalonia, Baltica and Gondwana close Iapetus
360Ma- Pangea forms
200Ma- Thulean plume opens up the Atlantic Ocean
What are the stages in rifting?
Extension- Rising melt causes crustal thinning
Subsidence- lithosphere cools and sags, creates accommodation space
What is the earthquake cycle?
Stages in the formation of an earthquake (easily drawn), where pressure builds up due to dragging down of a plate.
Further away from subduction experiences subsidence (Banda Aceh, Indonesia)
close experiences uplift (simeulue Island, Indonesia)
What is evidence for earthquakes?
- Changes in river location
- Movement of lake beds
- Movement of qanats (water extractors)
- Radio interferometry (satellites)
What are tsunamis?
Shallow water waves where wavelength is longer than the water depth, their speed is only dependent on depth
What are the effects of a tsunami and earthquake?
Lateral and vertical movement (uplift and subsidence) also in Japan, detected lateral movement of cities due to squeezing then stretching of plate
What are two types of basaltic eruptions?
Strombolian- large gas bubbles build up, shorter eruption duration
Hawaiian- Fountain like, on eruption time
What are the different regions in an eruption column?
Gas thrust region
Convective region
Umbrella region
How is the density changed in the eruption column?
Speed of ejection of ash
Amount of air entrained in the convective region
Radius of conduit, larger radius, greater area for air entrainment
What are the two types of rhyolitic eruptions?
Plinian- high up into the atmosphere, fast exit velocity and lots of entrainment of air, less dense
Vulcanian- collapse of ash column, slow exit velocity, denser = Pyroclastic flow
