Lecture 10- Mantel Plumes Flashcards
What is a lip?
Large igneous province
What is a lip?
The collective name for any form of basaltic intrusion that occurs AWAY from a MOR
What is an oceanic plateaux?
An unusually thick area of oceanic crust
Give the three key flood basalt, and when they occurred
-Siberian traps, 250 ma
Deccan traps, 65 ma
Columbia river, 15 ma
Where do most flood basalt occur?
At a seismic ridges (end of flood basalt chains)
Which flood basalt is linked to Yellowstone?
Columbia river
When did the Deccan traps erupt, an which plates were involved
63 to 69 ma, where a hotspot sat atop of the Indian plate
Which flood basalt was potentiall responsible for the Permian mass extinction?
The Deccan traps (63-69 ma)
Explain the plume model, giving values for temperature and depth
-anaonamouly hot material( 300-400 degrees greater than surroundings) rises buoyantly through the mantle. Plume has large head of 500-2000km and cooler, narrower tail. Decompressional meting of the head produces flood basalt, and once this has errupted, the tail creates a seismic ridges/hotspots as the plates move over it
How many flood basalt eruption in the last 250 ma coincided with mass extinctions?
9
When is plume activity high?
When the frequency of reversal of the earths magnetic field is low
When was Venus last resurface? What’s the evidence?
Approximately 400ma, and this is estimated by the lack of surface craters
What evidence is there against plate tectonic on Venus?
There’s lots of volcanoes ,but they are all isolated and in no defined chains. The lithosphere is too thin and the asthenosphere too close to the surface for plate movement
At what rate does the North American plate move over the Yellowstone hotspot?
25mm/yr
What are the four main greenhouse gasses errupted by volcanoes?
-h2o
-Co2
So2
Hcl
How to volcanic aerosols contribute to global cooling?
-scattering some of the incoming radiation back to space
What factors cause variation in the impacts of volcanic erruptions?
- latitude
- season
- magmatic composition (gas content)
- explosively
- length of eruption (more gas emitted)
- feedback effects
Give information on the 1991 mount pinatabo eruption
Occurred on the 15th June
-releases 30kg of aerosol in to the atmosphere
-global mean temperature had fallen by 0.5 degrees by 1992
Lots of sulphur dioxide from the magma released into the atmosphere
Give information on the 1815 tambora eruption
Errupted 5x more Aerosols than pinatabo
- caused global cooling of one degree across Europe the following year, and this was called the year without a summer
- triggered regional crop failures and famine, with 90000 people perishing that year
Give information on the 1783 lake fissure eruption in Iceland
- non explosive, basaltic magma
- one degree of cooling occurred in the northern hemisphere
- high emissions of s,f and cl gas
- these caused acid rain which destroyed crops and caused famines
give information on the toba eruption
-occurred 74 ka
-produced a 100km long caldera
-no evidence of associated mass extinctions within the fossil record
Caused a volcanic winter with notable cooling occurring for 1-2 years following
Give information on the Permian mass extinction
Occurred 250ma, and killed 90% of marine species and 70% of land vertebrates
When did Pangea assemble and when did it split up?
- 300 ma
- 200 ma