WEEK 11 - Mass Extinctions Flashcards
1
Q
Are mass extinctions caused by one event?
A
- Usually multiple factors
- Complex causes
- No single explanation fits all
2
Q
What are the common causes of mass extinctions?
A
- Asteroid impact
- Volcanism
- Sea level change
3
Q
Which extinction will be used to explore causes?
A
- Cretaceous-Tertiary (K-T) extinction
- Best studied
- Most famous (dinosaurs)
4
Q
WHAT IS K-T BOUNDARY?
A
Known as the Cretaceous-Tertiary boundary, marks the geological time when the Mesozoic Era ended and the Cenozoic Era began
Roughly 66 million years ago
It’s associated with the mass extinction event that wiped out the dinosaurs and many other species.
The boundary is a thin layer of rock, usually enriched in iridium, that can be found globally in various locations
5
Q
Where is the K-T boundary located?
A
- Gubbio, Italy
- Italian Apennine Mountains
6
Q
What marks the K-T boundary?
A
- A band of clay
- Break between limestone beds
- Dramatic change in fossil types
7
Q
What does the K-T boundary indicate?
A
- Interruption in sedimentation rate
- Change in fossil content
8
Q
What happens to planktic foraminifera above the K-T boundary?
A
- Small
- Low diversity
- Suggests high biological stress
9
Q
What happens to planktic foraminifera below the K-T boundary?
A
- Large
- Very diverse
- Suggests good living conditions
10
Q
What does the faunal change at Gubbio suggest?
A
- Dramatic change in size and diversity
- Biological crisis occurred at K-T boundary
- Marks extinction of dinosaurs on land
11
Q
What is the “Iridium Spike” at the K-T boundary?
A
- Dramatic increase in iridium (platinum-group element)
- Detected worldwide
12
Q
Who first noted the Iridium Spike at the K-T boundary and how?
A
- Luis and Walter Alvarez in 1980
- Suggested asteroid/comet impact caused the Iridium spike
13
Q
What does the Iridium Spike indicate?
A
- Iridium is rare on Earth but common in asteroids
- Supports hypothesis of an asteroid impact causing K-T extinction
- High concentration of iridium at K-T boundary known as the “Iridium Spike”
- Large impact by comet or asteroid
- Linked to Cretaceous-Tertiary mass extinction
14
Q
What is shocked quartz?
A
- Quartz with unique structures formed by extreme pressure
- Seen at meteorite impact sites and nuclear test sites
15
Q
Where is shocked quartz found in relation to the K-T boundary?
A
- Found in K-T boundary clay
- Indicates shock metamorphism
16
Q
What does the presence of shocked quartz suggest?
A
- Strong impact event
- Support for asteroid/comet impact theory at the K-T boundary
17
Q
What are tektites?
A
Tiny spherules of glass
18
Q
How are tektites formed?
A
- Formed by melting from extreme heat during an impact event
- Melted rock from the impact is flung into the atmosphere as droplets
- Quickly cooled in the atmosphere to form glass beads
19
Q
Where are tektites found?
A
Found worldwide at the K-T boundary
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23
24
What do tektites suggest about the K-T event?
- Evidence for a meteorite impact
- Tektites support the theory of an asteroid/comet impact at the K-T boundary
25
What does the presence of soot support?
- Evidence for wildfires caused by impact heat
- Further supports the meteorite impact theory for the K-T extinction event
25
What does the "Fern Spike" suggest?
- Recovery of forests after a major event
- Ferns are the first plants to recolonize after wildfires or deforestation
25
What are soot particles?
Mixtures of burnt organic matter and glass
25
Where are soot particles found?
Found worldwide at the K-T boundary
25
What do soot particles indicate?
- Intense heating of materials at the K-T boundary
- Possible wildfires ignited by the heat of the impact
25
What is the "Fern Spike"?
- Sharp drop in % tree pollen
- Sharp rise in % fern spores
26
What does the "Fern Spike" indicate about the impact event?
- Linked to global wildfires caused by the impact
- Deforestation from the heat and destruction
27
How does the "Fern Spike" correlate with Iridium levels?
- Fern spores increase as Iridium levels (evidence of impact) rise
- Suggests connection between impact event and ecological changes
28
Who discovered the Chicxulub Crater?
- Alan Hildebrand, Canadian Geologist, in 1991
- Geophysicist working for Petróleos Mexicanos had noticed it in 1978, but data was proprietary
29
What is the significance of the Chicxulub Crater?
- It is the "smoking gun" linked to the K-T extinction event
- The crater's size and age match the global catastrophe associated with the K-T boundary
30
How was the Chicxulub Crater discovered?
- Discovered through geophysical surveys
- Revealed by data pointing to a massive impact event
31
What is the size of the Chicxulub Crater?
- At least 180 km in diameter
- Buried beneath Cenozoic sediments
32
How is the Chicxulub Crater mapped?
Mapped using geophysical surveys due to burial under sediments
33
What does the structure of the Chicxulub Crater look like?
- Multiple rings with a dome in the center
- Typical form for large impact craters
34
What size was the impacting object (asteroid) at Chicxulub?
- The impacting object was an asteroid
- Estimated about 10 km in diameter
35
What was the energy released by the Chicxulub impact?
100 million megatons of energy released
36
How did the Chicxulub impact affect Earth's atmosphere?
- Debris ejected into the atmosphere
- Caused extreme particulate pollution
- Plunged Earth into darkness and cold for several months
37
What effect did the Chicxulub impact have on photosynthesis?
- Shut off photosynthesis
- Led to a cascade of death throughout the biosphere
38
What was released due to the impact at the Yucatán Peninsula?
Vaporization of gypsum (calcium sulfate)
Yellow = gypsum
39
What did the gypsum vaporization produce?
- Generated lots of sulfur dioxide
- Lowered global temperatures for several years
40
How did sulfur dioxide affect the atmosphere?
- Reacted with water to produce severe acid rain
- Made it hard for marine organisms to produce calcite skeletons
41
What did combustion of nitrogen in the atmosphere cause?
- Produced nitrogen oxides
- Contributed to acid precipitation (as nitric acid)
42
How did the impact affect the ozone layer?
- Reduced ozone levels in the atmosphere
- Increased vulnerability to harmful UV radiation
43
What could survivors have faced after freezing?
Frying due to increased UV radiation from ozone depletion
44
Other Effects of Impact
Darkness and cold from debris blocking sunlight (impact winter).
Disruption of photosynthesis, leading to biosphere collapse.
Massive sulfur dioxide release, lowering global temperatures.
Acid rain from sulfur dioxide, harming marine organisms' ability to form calcite skeletons.
45
Volcanism's Role in Mass Extinction
- Massive lava flows and volcanic gases (e.g., CO2) released into the atmosphere.
- Possible contribution to global warming or environmental disruption.
- Volcanic activity can impact ecosystems over long periods.
46
What was the impact of the Deccan Traps volcanism?
- Huge volcanic eruptions in India near the end of the Cretaceous period.
~4 million cubic km of lava erupted over 2 million years.
- Released sulfur dioxide, cooling the global climate.
- Contributed to environmental stress before the asteroid impact.
47
How did the Deccan Traps contribute to global cooling?
- Volcanic gases, particularly sulfur dioxide, formed aerosols in the atmosphere.
- Aerosols reflected sunlight, cooling the planet.
- This cooling would have stressed ecosystems further, making the impact of the asteroid more devastating.
48
What was the climate like during the Cretaceous Period?
- Warm global climate, with no polar ice caps.
- Large areas of continents were covered by shallow seas.
- The warm climate contributed to high sea levels.
49
How did rising sea level changes affect the Cretaceous Period?
- Rising sea levels created shallow seas, covering large parts of continents.
- Sea level changes likely influenced ecosystems and biota.
- Fluctuations in sea levels might have contributed to environmental stresses leading up to the mass extinction.
50
What happened when sea levels dropped at the end of the Cretaceous Period?
- Major drop in sea levels between the Cretaceous and Tertiary (Paleogene) Periods.
- Shallow marine habitats were removed as shallow seas drained.
- Continental shelf areas were exposed.
51
How did the sea level drop affect marine organisms?
Extinction of some shallow marine organisms due to loss of habitat.
52
How did the sea level drop affect land organisms?
More arid land areas led to extinction of land organisms that needed large wetland areas.
53
How did low sea levels create land bridges?
- Lower sea levels exposed land bridges between continents.
- Some continents were still close together at the time.
54
What were the effects of land bridges on animal migration?
- Land bridges allowed animals to migrate across continents.
- Migration could have led to competition between species.
55
How might land bridges have contributed to the spread of disease?
Migration across land bridges may have spread diseases among land animals.
56
What marked the end of the K-T mass extinction?
- The K-T extinction led to the end of the dinosaurs' reign.
- It ushered in a new age, with significant changes in life forms.
57
What was the significance of the demise of dinosaurs?
- The extinction of dinosaurs allowed mammals to thrive and evolve.
- True mammals appeared in the Jurassic Period but their ancestors predate dinosaurs.
58
What type of organisms thrived after the K-T extinction?
Mammals, which were previously overshadowed by dinosaurs, began to evolve more prominently.
59
How did mammals benefit from the K-T extinction?
- Mammals, once small and overshadowed by dinosaurs, began to thrive.
- With the dinosaurs gone, mammals filled ecological niches, leading to their rapid evolution.
60
How important was the K-T extinction for the evolution of mammals?
Without the K-T extinction, mammals may not have evolved as they did, and humans may not have emerged.
61
What are the environmental issues contributing to the current mass extinction?
Atmospheric pollution (fossil fuel use)
Habitat loss (deforestation, monoculture)
Ozone depletion (CFCs)
Rising sea levels (fossil fuel use)
Acid precipitation (fossil fuel use)
Disease epidemics (spread via air travel)
62
How is today's extinction event similar to the Cretaceous-Tertiary extinction?
- Both involve rapid environmental changes due to external factors (e.g., pollution, habitat loss).
- Human activities mirror the catastrophic effects of past mass extinctions (e.g., the K-T event).
