magma chamber n intrusive igneous rocks n magma chamber is intermittent
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Magma ChamberMagma Chamber Intrusive igneous rocksIntrusive igneous rocks magma chamber is intermittentmagma chamber is intermittent
Idealized Ophiolite StructureIdealized Ophiolite Structure
Layer numbers correspond to acoustic speedsLayer numbers correspond to acoustic speeds depths are typicaldepths are typical
More Realistic More Realistic Spreading Spreading
Center SectionCenter Section
Note :Note : failed magma chambersfailed magma chambers complexity of intrusive layerscomplexity of intrusive layers
Fractionation takes place until the Fractionation takes place until the last magma has solidifiedlast magma has solidified the pressure where it happens the pressure where it happens
determines chemistry / mineral determines chemistry / mineral compositioncomposition
Effects of Plate TectonicsEffects of Plate Tectonics Remember that seafloor subsides with age due to cooling and Remember that seafloor subsides with age due to cooling and
thickening of the lithospherethickening of the lithosphere same rate of subsidence in any oceansame rate of subsidence in any ocean
Age vs Depth CurvesAge vs Depth Curves
Linear when plotted vs Linear when plotted vs square rootsquare root
only works to 60 million only works to 60 million yearsyears
Topography as Topography as f(spreading rate)f(spreading rate)
Faster spreading = shallower topographyFaster spreading = shallower topography
Tectono-eustatic Sea LevelTectono-eustatic Sea Level
Formation of GuyotsFormation of Guyots
Happens on any plate, Happens on any plate, regardless of climateregardless of climate
Atoll / Guyot AnimationAtoll / Guyot Animation
Atoll StructureAtoll Structure
Diego Garcia, British Indian Ocean TerritoryDiego Garcia, British Indian Ocean Territory
CaCOCaCO33 Accumulation Accumulation CaCOCaCO33 chemistry causes it to dissolve at depth chemistry causes it to dissolve at depth
results in a “snow line”results in a “snow line”
CaCOCaCO3 3 DepositionDeposition
This pattern is evident in most oceansThis pattern is evident in most oceans depends a little on biological productivitydepends a little on biological productivity
Hot SpotsHot Spots Deep sources of extra-hot magmaDeep sources of extra-hot magma rise up through mantlerise up through mantle are cause of intra-plate volcanismare cause of intra-plate volcanism
YellowstoneYellowstone
Formation of the Island ChainsFormation of the Island Chains
As plate passes over source of volcanism, a chain of As plate passes over source of volcanism, a chain of islands is formedislands is formed
Island ChainsIsland Chains For example, For example,
the Hawaiian the Hawaiian IslandsIslands
Note agesNote ages Ancient Ancient
Hawaiians Hawaiians noticed thisnoticed this referred to it referred to it
as Pele as Pele moving from moving from island to island to islandisland
Hawaiian / Emperor Seamount ChainHawaiian / Emperor Seamount Chain
All produced by All produced by the same hot the same hot spotspot
age progresses age progresses uniformly out uniformly out the chainthe chain
plate motion plate motion changed to changed to produce the produce the bend in the bend in the chainchain
Hawaiian / Emperor Seamount ChainHawaiian / Emperor Seamount Chain
Age Age progresses progresses well all the well all the way outway out
some error in some error in age age determinationdetermination
Hot Spot TracesHot Spot Traces
The Hawaiian The Hawaiian Islands are only Islands are only one exampleone example
each hot spot each hot spot under the Pacific under the Pacific plate produces an plate produces an island chainisland chain
IcelandIceland Hot spot Hot spot
and ridge and ridge axis co-axis co-locatedlocated
double dose double dose of of volcanismvolcanism
““Twin Aseismic RidgesTwin Aseismic Ridges If the hot spot becomes dormant (dies), the volcanism ceases If the hot spot becomes dormant (dies), the volcanism ceases
but spreading continuesbut spreading continues results in twin ridgesresults in twin ridges
Plate Plate Positions Affect CirculationPlate Plate Positions Affect Circulation
Terminal Eocene EventTerminal Eocene Event
At the end of the Eocene, the Drake Passage opened At the end of the Eocene, the Drake Passage opened upup
This allowed circum-Antarctic circulation for the first This allowed circum-Antarctic circulation for the first timetime
Circulation Circulation in the in the Southern Southern Ocean was Ocean was strongly strongly affectedaffected
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