Mass Extinctions

Question 1

What defines a mass extinction?

Answer 1

A huge fraction of life goes extinct over a very short period of time (less than a million years)

Question 2

How do mass extinctions change life on earth?

Answer 2

They fundamentally alter evolutionary pathways, like enabling mammals to diversify after the K-T extinction

Question 3

What are the main causes of mass extinctions?

Answer 3

Biological, physical terrestrial events, and extraterrestrial events (e.g. asteroid impacts or supernova)

Question 4

Give an example of biological causes of extinction

Answer 4

Early photosynthesis releasing massive amounts of oxygen ~ 2 billion years ago

Question 5

What are the “Big Five” extinction events?

Answer 5

Ordovician-Silurian, Late Devonian, Permian-Triassic, Triassic-Jurassic, and Cretaceous-Tertiary (K-T)

Question 6

When did the Ordovician-Silurian extinction occur and what was its impact?

Answer 6

~444 million years ago, the third largest extinction event and second largest for marine life

Question 7

What is significant about the Late Devonian extinction?

Answer 7

Occurred ~ 364 MYA, restricted marine life, associated with the Siljan Ring impact crater in Sweden

Question 8

Which extinction is known as the “Great Dying” and why?

Answer 8

The permian-Triassic extinction (~251 MYA); 96% of marine species and 70% of terrestrial vertebrates went extinct

Question 9

What role did the Siberian traps play in the Permian-Triassic extinction?

Answer 9

One of the largest volcanic scents in the last 500 MY, altering climate and chemistry

Question 10

What happened during the Triassic-Jurassic extinction (~ 200 MYA)?

Answer 10

50% of species went extinct, opening niches for dinosaurs to dominate

Question 11

What caused the Cretaceous-Tertiary (K-T) extinction (~65.6 MYA)?

Answer 11

An asteroid/comet impact at chicxukub crater, possibly combined with volcanic events

Question 12

What is the Quaternary extinction, and what caused it?

Answer 12

Extinction of megafauna ~11,000-50,000 years ago, possibly due to human hunters, climate change, or an impact event

Question 13

Who proposed the idea of humans causing megafaunal extinctions?

Answer 13

Paul Martin (University of Arizona)

Question 14

What are some potential causes of future mass extinctions?

Answer 14

Supervolcanoes, gamma-ray bursts, early supernova, asteroid impacts, and human activities

Question 15

What is a supervolcano and what past event is linked to extinction?

Answer 15

A massive volcanic eruption; the Siberian traps contributed to the Permian Triassic extinction

Question 16

What is the Toba supervolcano and why is it significant?

Answer 16

Erupted ~70,000-75,000 years ago, potentially reducing human populations to a bottleneck of 1,000-10,000 breeding pairs

Question 17

How could a nearby supernova cause mass extinction?

Answer 17

It could strip Earth’s ozone layer, exposing life to harmful radiation

Question 18

What are two notable asteroid/comet impact events on earth?

Answer 18

Tunguska (1908) and Chelyabinsk (2013)

Question 19

What happened during the Tunguska event?

Answer 19

A ~65-meter object exploded, flattening 80 million trees over 2,150km sq

Question 20

What is significant about the Chicxulub impact?

Answer 20

It is linked to the extinction of dinosaurs during the K-T event

Question 21

What role do gamma-ray bursts play in extinction risks?

Answer 21

It could release jets of radiation, devastating earths biosphere