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

C-Mass Extinctions P1 Flashcards

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Biology 101 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
Q

Structure of lithology of Chicxulub Crater from bottom to top (5)

A

Melt Rock - Suevite breccia (impactites) - 50cm sediments - K-t boundary clay - younger sediments

26
Q

What were the names of the 2 drill cores tacken form the Chicxulub Crater?

A

Chicxulub 1

Yucatan 6

27
Q

Suevite (Suevite Breccia) (

A

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
Q

What is both within and adjacent to the Chicxulub Crater?

A

Suevite (breccia) and melt rock

29
Q

What did the Chicxulub ejecta blanket do? (Where) (2)

A

Ejected fragments away from crater

Found in Belize, 350km S of crater

30
Q

What is proximal ejecta?

A

Particles settled after impact around Caribbean (ejecta blanket)

31
Q

What were the 50 cm/0.5m sediments?

A

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
Q

Mass Wasting Deposits (

A

Eg. Landslides

Mainly in Caribbean and eastern seaboard of South and especially N America

33
Q

What are the different taxonomic levels from largest to smallest? (4)

A

Phylum - Class - Order - Family (- Genus - Species)

34
Q

When did the K-T event occur?

A

65mya

35
Q

What are the 2 interpretations of the K-T event?

A

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
Q

What is the main difference between the 2 interpretations?

A

2nd interpretation suggests that there was 2 impacts

37
Q

What is the possible complication with the Chicxulub impact?

A

It may pre-date the K-T boundary by 300,000 years (occurred at 65.3mya) - not definite

38
Q

Does all of this evidence prove that the impact resulted in extinction?

A

No - need to look at killing mechanisms (indirect)

39
Q

What are the indirect killing mechanisms that most likely result from a bolide impact? (4)

A

Severe reductions of light levels
Changes of temps
Acid rain
Wildfires

40
Q

What occurred in the minute, hours, days and years after the impact? (4)

A

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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