What level are mass extinctions measured at?
Family
What are the “Big Five” mass extinction events?
End Ordovician
Late Devonian
End Permian (largest)
End Triassic
End Cretaceous (K–T / K–Pg)
What extinction patterns can be observed in the fossil record?
Abrupt (sudden disappearance)
Gradual (progressive decline)
Step‑like (multiple pulses)
What is a bolide, and how does it differ from an asteroid?
A bolide is any extraterrestrial body entering Earth’s atmosphere.
An asteroid is a rocky/metallic bolide >1 m in size.
What is the iridium (Ir) anomaly and why is it significant?
Iridium is rare in Earth’s crust but common in meteorites. A global spike in Ir concentration at the K–T boundary strongly supports extraterrestrial impact.
What does the thin K–T boundary clay layer represent in stratigraphic sections?
A globally distributed, fine‑grained layer deposited rapidly after impact. It often hosts iridium, shocked minerals, impact glass, and fern spores.
What are tektites and what do they indicate?
Microscopic natural glasses formed by rapid quenching of molten ejecta at very high pressure and temperature.
Their low water content indicates formation in dry, extreme conditions.
What is shocked quartz and why is it diagnostic of impact?
Quartz containing multiple sets of planar deformation features that only form under extreme shock pressures (>5–10 GPa), typical of meteorite impacts.
What is stishovite?
A high‑pressure polymorph of quartz
What does the “fern spike” indicate in pollen/spore diagrams?
A short‑lived dominance of fern spores immediately after the K–T boundary, reflecting ecological recovery under low‑light, disturbed conditions.
Where is the Chicxulub crater and why is it considered the “smoking gun”?
Located beneath the Yucatán Peninsula. Its size (>150 km diameter), age, and associated ejecta match the K–T boundary precisely.
How do gravity and aeromagnetic anomaly maps reveal the Chicxulub crater?
Low‑density breccias and melt rocks produce distinct gravity lows and magnetic anomalies, revealing buried crater morphology.
What is suevite?
A polymict impact breccia containing shocked and unshocked clasts and melt particles, deposited close to the impact site.
What is the debate over the 50 cm sediment layer above suevite?
Interpretation 1: Instantaneous backwash after impact
Interpretation 2: Slow marine sedimentation between two impacts
Most evidence supports a single impact.
What direct killing mechanisms are associated with impact?
Heat pulse, blast effects, wildfires, tsunami devastation near impact site.
What indirect killing mechanisms are associated with impact?
Nuclear winter (dust‑blocked sunlight), global cooling, acid rain, ecosystem collapse, followed by greenhouse warming.
What terrestrial alternatives to impact are proposed for the K–T extinction?
Eustatic sea‑level change
Climate change
Flood basalt volcanism (Deccan Traps)
What do diagrams of Large Igneous Provinces (LIPs) show?
Temporal coincidence between mass extinctions and major volcanic episodes, implying volcanic gas release as a killing mechanism.
Why are Deccan Traps significant?
Enormous flood basalt province releasing CO₂ and SO₂
What is a sedimentary hiatus and how does it affect extinction interpretation?
A gap in deposition that can make gradual extinctions appear abrupt in the stratigraphic record.
What is the Signor–Lipps effect?
The last appearance of a species in the fossil record almost always predates its true extinction, artificially smearing abrupt events.
What are Lazarus taxa?
Taxa that temporarily disappear from the fossil record and later reappear due to migration or local extinction, not true extinction.
How do diagrams distinguish Lazarus taxa from true extinction?
By showing survival in unsampled regions or environments before later re‑entry into the studied section.
What are Elvis taxa?
Newly evolved taxa that resemble extinct forms, falsely suggesting survival of original species.
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Origin of the Solar System15
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Structure of the Earth17
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The development of plate tectonics15
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surface processes;making new rocks30
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Rocks from melts15
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Metamorphism22
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Plate tectonic and climate shaping ireland44
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Geobiology: Life as a geological force33
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Origin of Life on Earth18
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The rise of oxygen11
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Snowball Earth11
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Rise of the Animals13
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Colonisation of Plants17
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Mass Extinction27
