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Intro to Earth Science > C-Mass Extinctions P1 > Flashcards

C-Mass Extinctions P1 Flashcards

1
Q

What is the fossil record?

A

A direct, imperfect history of the evolutionary history of life of Earth- includes record of extinction

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2
Q

Give 2 examples of extinct animals

A

Dodo bird

The Irish elk (Megaloceros)

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3
Q

Why do people believe we are currently in the 6th mass extinction?

A

Many authorities believe that the current rate of species extinction merits that title

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4
Q

What is an indirect action that is causing this 6th mass extinction?

A

Climate Change

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5
Q

What is a direct action that is causing this 6th mass extinction?

A

Overhunting, destroying habitats etc

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6
Q

What will shape our response to the current biotic crisis?

A

Understanding the causes and effects of previous mass extinction events

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7
Q

How any mass extinction events has there been?

A

5

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8
Q

What is one idea of what can cause a mass extinction?

A

Asteroids - bolide impact

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9
Q

Name the 5 mass extinctions from oldest to youngest.

A 
End/Late Ordovician
End/Late Devonian
End Permian (P-Tr)
End/Late Triassic (end Tr)
End Cretaceous (K-T)
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10
Q

Which taxonomic level determines can be used to identify the total rate of extinction? (extinction metric)

A

Family

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11
Q

What occurred in the K-T event? (5)

A

End of the Cretaceous
Extra-terrestrial bolide impact on earth = 1st wave of destruction
Tsunami destroys all coastlines near impact site
Atmospheric debris - Earth covered by shroud of dust
Crater of Doom - immense crater after sunlight returns to earth

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12
Q

What are the key points about the K-T event?

A

External to Earth System
No reason to assume biotic stress on Earth before impact
Sudden event
Global effect from local source

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13
Q

What evidence is there of of an impact? (11)

A 
Iridium (Ir) anomaly
Boundary Clay
Tektites
Shocked Quartz
Impact glass
Stishovite
Tsunami deposits
Fern Spike
Chicxulub Crater
Suevite
Mass Wasting deposits
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14
Q

What is a bolide?

A

An extra-terrestrial body

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15
Q

Iridium Anomaly (3)

A

Low abundance on Earth - abundant in meteorites
Supplied from space - low abundance in sedimentary record
Anomaly= elevated abundance found in K-T boundary sections (global distribution?)

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16
Q

Boundary Clay (4)

A

Thin, fine-grained layer
Global distribution (marine and terrestrial)
Usually distinct from lithologies above and below
Hosts other evidence - Ir anomlay, tektites. impact glass etc

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17
Q

Give 2 examples of locations for boundary clay

A

Terrestrial: Zahurski’s Point, Grasslands National Park
Marine: Contessa, Italian Appenines

18
Q

Tektites (4)

A

Natural glass - microscopic size
Shapes suggest cooled rapidly while moving
Low water content - can include partially melted zircons
Suggests formations at very high Pressure (P) and Temps (T)

19
Q

Shocked Quartz (3)

A

Unusual microstructure
Cross-cutting shock lamellae
Deformation of crystal structure

20
Q

Impact Glass (2)

A

Rapid quenching of molten droplets

Found at base of K-T sequence in Gulf of Mexico

21
Q

Stishovite (1)

A

High temperature polymorph of quartz

22
Q

Tsunami Deposits (3)

A

Rapid (geologically instantaneous) deposition of sediments after events such as earthquakes
Example in NE Mexico (bottom = impact layer, middle = coarse sandy tsunami deposit, top = siltstone, claystone with Ir Anomaly)
Spatial distribution: Concentrated in Caribbean Region

23
Q

Fern Spike (2)

A

Short-lived high increase in abundance of fern spores at K-T boundary
Adapted to low light consitions

24
Q

The Chicxulub Crater (3)

A

Asteroid = 10-15km diameter
Crater = >150km diameter (up to 80km radius)
All info bases on seismic studies

25
Structure of lithology of Chicxulub Crater from bottom to top (5)
Melt Rock - Suevite breccia (impactites) - 50cm sediments - K-t boundary clay - younger sediments
26
What were the names of the 2 drill cores tacken form the Chicxulub Crater?
Chicxulub 1 | Yucatan 6
27
Suevite (Suevite Breccia) (
Melting and solidification in situ Formed and deposited relatively close to impact crater Impact breccia with varied clasts (polymict) Contains shocked and unshocked clasts and melt particles
28
What is both within and adjacent to the Chicxulub Crater?
Suevite (breccia) and melt rock
29
What did the Chicxulub ejecta blanket do? (Where) (2)
Ejected fragments away from crater | Found in Belize, 350km S of crater
30
What is proximal ejecta?
Particles settled after impact around Caribbean (ejecta blanket)
31
What were the 50 cm/0.5m sediments?
Single geology event bed after impact Interpretation 1: they were an instant backwash of water borne sediments into crater Interpretation 2: Build-up of marine sediments inside impact crater between events
32
Mass Wasting Deposits (
Eg. Landslides | Mainly in Caribbean and eastern seaboard of South and especially N America
33
What are the different taxonomic levels from largest to smallest? (4)
Phylum - Class - Order - Family (- Genus - Species)
34
When did the K-T event occur?
65mya
35
What are the 2 interpretations of the K-T event?
1) impact - instant backwash of water-borne sediments into crater (50cm sediments) - rapid settling out of finer grained sediments 2) impact - slow build up of marine sediments inside impact crater (50cm sediments) - rapid settling out of finer grained sediments after 2nd impact
36
What is the main difference between the 2 interpretations?
2nd interpretation suggests that there was 2 impacts
37
What is the possible complication with the Chicxulub impact?
It may pre-date the K-T boundary by 300,000 years (occurred at 65.3mya) - not definite
38
Does all of this evidence prove that the impact resulted in extinction?
No - need to look at killing mechanisms (indirect)
39
What are the indirect killing mechanisms that most likely result from a bolide impact? (4)
Severe reductions of light levels Changes of temps Acid rain Wildfires
40
What occurred in the minute, hours, days and years after the impact? (4)
Minutes/Hours after: Energy pulse, wildifre, ejecta Days-10 years: Fern survivors, low light, cool temps 10-500 years: Successional ferns and angiosperms, enhanced light greenhouse warming 500-10,000 years: re-generating canopy, near pre-boundary conditions

Intro to Earth Science (13 decks)

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