Lecture 10- Mantel Plumes

Question 1

What is a lip?

Answer 1

Large igneous province

Question 2

What is a lip?

Answer 2

The collective name for any form of basaltic intrusion that occurs AWAY from a MOR

Question 3

What is an oceanic plateaux?

Answer 3

An unusually thick area of oceanic crust

Question 4

Give the three key flood basalt, and when they occurred

Answer 4

-Siberian traps, 250 ma
Deccan traps, 65 ma
Columbia river, 15 ma

Question 5

Where do most flood basalt occur?

Answer 5

At a seismic ridges (end of flood basalt chains)

Question 6

Which flood basalt is linked to Yellowstone?

Answer 6

Columbia river

Question 7

When did the Deccan traps erupt, an which plates were involved

Answer 7

63 to 69 ma, where a hotspot sat atop of the Indian plate

Question 8

Which flood basalt was potentiall responsible for the Permian mass extinction?

Answer 8

The Deccan traps (63-69 ma)

Question 9

Explain the plume model, giving values for temperature and depth

Answer 9

-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

Question 10

How many flood basalt eruption in the last 250 ma coincided with mass extinctions?

Answer 10

9

Question 11

When is plume activity high?

Answer 11

When the frequency of reversal of the earths magnetic field is low

Question 12

When was Venus last resurface? What’s the evidence?

Answer 12

Approximately 400ma, and this is estimated by the lack of surface craters

Question 13

What evidence is there against plate tectonic on Venus?

Answer 13

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

Question 14

At what rate does the North American plate move over the Yellowstone hotspot?

Answer 14

25mm/yr

Question 15

What are the four main greenhouse gasses errupted by volcanoes?

Answer 15

-h2o
-Co2
So2
Hcl

Question 16

How to volcanic aerosols contribute to global cooling?

Answer 16

-scattering some of the incoming radiation back to space

Question 17

What factors cause variation in the impacts of volcanic erruptions?

Answer 17

• latitude
• season
• magmatic composition (gas content)
• explosively
• length of eruption (more gas emitted)
• feedback effects

Question 18

Give information on the 1991 mount pinatabo eruption

Answer 18

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

Question 19

Give information on the 1815 tambora eruption

Answer 19

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

Question 20

Give information on the 1783 lake fissure eruption in Iceland

Answer 20

• 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

Question 21

give information on the toba eruption

Answer 21

-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

Question 22

Give information on the Permian mass extinction

Answer 22

Occurred 250ma, and killed 90% of marine species and 70% of land vertebrates

Question 23

When did Pangea assemble and when did it split up?

Answer 23

• 300 ma

- 200 ma