End Permian and Cretaceous Extinctions

Question 1

When was the end Permian extinction event roughly?

Answer 1

250mya

Question 2

What was the state of Pangea at the start of the end Permian extinction?

Answer 2

Still largely together

Question 3

What are the two possible causes for the end Permian extinction and which is mostly recognised?

Answer 3

Extra-terrestrial (mostly ignored) and vulcanism (mostly accepted)

Question 4

What evidence is there for an end Permian extinction being caused by extra-terrestrial impact?

Answer 4

Discovery of a crater in Australia that contained:
quartz structures
fullerenes with argon and helium isotopes that suggested extra-terrestrial source.

Question 5

What were the two problems with the evidence for the end Permian extinction event being caused by an extra-terrestrial impact?

Answer 5

No iridium present (key)

Fullerene results were not reproducible

Question 6

What are the two ways that vulcanism could have caused the end Permian extinction?

Answer 6

Ozone layer alterations

GHG and temperature increase

Question 7

Explain how the ozone layer alterations caused by vulcanism could have caused the end Permian extinction?

Answer 7

The release of gases and volatiles in to the atmosphere from the volcanic source could have altered the ozone layer and allowed more UV light to penetrate the terrestrial sphere leading to mutagenesis for plants

Question 8

What was the source of the volcanic activity that caused the end Permian extinction?

Answer 8

Siberian Traps

Question 9

What area did the Siberian traps lava flows cover, what volume were the flows, how deep were they and how many years did they erupt over?

Answer 9

Area covered: 1.6mn km^2
Volume: 2mn km^2
Depth: 3km
Duration of eruption: 1 million years (tens of thousands of years?)

Question 10

How would the Siberian traps have increased atmospheric GHG concentration?

Answer 10

As the lava flows from deep rise up through the crust they cooked the organic 12C-rich sediment layers which were then released in to the atmosphere

Question 11

By how many degrees Celsius did the temperature of the atmosphere rise by following the release of organic carbon by rising lava flows?

Answer 11

10 Degrees Celsius

Question 12

What evidence is there for how the vulcanism cooked the organic carbon sedimentary layers?

Answer 12

Because the biosphere mostly prefers 12C, this is what was mostly stored in the sedimentary layers. When the lava flows cooked this layer rich in 12C it was all released to the atmosphere where it was then once again consumed rapidly by plants that prefer the 12C which had become re-available for use in photosynthesis. This meant when the biosphere from the period of the Siberian traps eruptions decomposed, there was another layer of organic carbon rich in 12C.

Question 13

How did the high GHG (CO2 concentration) affect oceans and then cause the end Permian extinction event within the oceans?

Answer 13

The high CO2 concentration would have meant that a lot would have dissolved in to the oceans which would have acidified it to a large degree. This is bad for calcifying organisms such as organisms that produce carbonate/foraminifera shells that were found to have declined in production

Question 14

What happened just before the oceans in the end Permian extinction event acidified?

Answer 14

They became increasingly anoxic

Question 15

What evidence was there of the oceans becoming more anoxic just before the end Permian extinction event?

Answer 15

Disappearance of larger and more complex organisms from the record and rise of hydrogen sulphide, which only happens when oxygen declines

Question 16

What are the two causes for the ocean becoming increasingly anoxic just before the end Permian extinction event?

Answer 16

1. Vulcanism

2. Temperature

Question 17

How does vulcanism cause the ocean to become increasingly anoxic just before the end Permian extinction event?

Answer 17

Vulcanism produces lava flows, rich in phosphorus, that get washed to oceans because of solubility, it fuels marine biosphere productivity of oxygen in a short burst, oxygen consumed by organisms at great depths but no more eruptions means that there is no more oxygen produced but because the organisms are now hungry for oxygen it continues to be consumed but not replenished

Question 18

How does increased temperature lead to anoxia at the end Permian extinction?

Answer 18

Increased temperature means CO2 dissolves less in oceans, this means less supply of sole oxygen element to oceans because it is not being split from a carbon molecule and so the ocean becomes anoxic in nature

Question 19

What was the impact of the end Permian extinction event upon marine, continental and total biodiversity?

Answer 19

Marine loss: 49%
Continental loss: 63%
total: 61%

Question 20

What impact did the end Permian extinction even have upon flora and geology?

Answer 20

forests were eradicated and replaced by fern types which meant erosion rates increased

Question 21

What was the only animal left after the end Permian extinction?

Answer 21

lystrosaurus

Question 22

How long did it take for ecosystems and biodiversity to recover after the end Permian extinction?

Answer 22

Ecosystems: 10myr

Biodiversity 100myr

Question 23

What fauna emerged after the end Permian extinction?

Answer 23

Dinosaurs and gymnosperm plants. More mobile to non-mobile fauna and more predators to prey

Question 24

When was the end cretaceous extinction event?

Answer 24

66mya

Question 25

What is another name for the end cretaceous extinction?

Answer 25

K/T or KPG

Question 26

What was the state of Pangea like at the end cretaceous extinction?

Answer 26

Close to today levels

Question 27

What are the two primary causes for the end Permian extinction event?

Answer 27

Extra-terrestrial impact

Vulcanism

Question 28

What evidence is there for the end cretaceous extinction event being caused by an extra-terrestrial impact?

Answer 28

Alvarez & Alvarez (1980) found a strong iridium content in the geology which later Hildebrand supported by finding a crater in the same place.

Question 29

Explain how the vulcanism caused the end cretaceous extinction event?

Answer 29

Eruption of large igneous province led to release of GHG and the consequent increase in the atmosphere.

Question 30

What was the source of the vulcanism that caused the end cretaceous extinction event? What volume were the lava flows and what duration did they erupt over?

Answer 30

Deccan Traps had a volume 365,000km^2 and erupted over 800kya

Question 31

What was the secondary cause for the end cretaceous extinction?

Answer 31

Reducing photosynthesis activity and shutting off of the biological pump

Question 32

What were the two proposed causes for the reduced photosynthesis activity?

Answer 32

1. Anoxia of the oceans (Vulcanic activity and temperature)

2. Debris from asteroid preventing insolation

Question 33

What impact did the shutting off of the photosynthesis activity have?

Answer 33

The shutting off of photosynthesis meant that nanoplankton species declined and so where they would have absorbed CO2 at the surface then decomposed and sunk to the ocean depths this no longer happened because they no longer existed.

Question 34

What was the process by which carbon was no longer transported to the bottom of the oceans by decomposing nanoplankton?

Answer 34

Shutting off of the biological pump

Question 35

What % of nanoplankton species died?

Answer 35

90%

Question 36

What impact did the shutting off of the biological pump have upon climate and calcifying organisms?

Answer 36

No CO2 being transported to the depths meant calcifying organisms at depths would not receive carbon they needed to form carbonate shells, and because the carbon was now accumulating at the top of the surface this meant it was better able to escape to the atmosphere which it did (leading to a 2-3X increase in atmospheric CO2) adding to the GHG released by the Deccan Traps.

Question 37

What impact did the end cretaceous extinction have upon fauna?

Answer 37

Dinosaurs extinct and only burrowing species survived such as crocodiles

Question 38

What impact did the end cretaceous extinction have upon flora?

Answer 38

Evergreen vegetation suffered while high-altitude colder climate vegetation survived