Mass Extinctions Pt 2

Which mass extinction was the largest in history?

The End-Permian (P-T), about 252 million years ago.

Main cause of the End-Permian extinction?

Massive volcanism in the Siberian Traps releasing CO₂, causing global warming, ocean anoxia, and acidification.

What was the K-T (Cretaceous-Paleogene) extinction?

Extinction event ~66 million years ago that wiped out ~76% of species, including non-avian dinosaurs.

What caused the K-T extinction?

A combination of massive volcanism and a giant asteroid impact.

What evidence supports the Alvarez Hypothesis?

Iridium layer at K-T boundary, shocked quartz, impact breccia, spherules, tsunami deposits, and the Chicxulub crater.

Who proposed the Alvarez Hypothesis?

Luis Alvarez (physicist) and Walter Alvarez (geologist).

Where was the K-T boundary first studied?

In rock samples from the Italian Apennine Mountains.

What does “necessary condition” mean?

A condition without which an event cannot occur.

What does “sufficient condition” mean?

A condition that guarantees that an event has occurred.

Example of necessary vs. sufficient conditions?

Gas is necessary for a car to run but not sufficient; no gas is sufficient to make it stop running.

What makes organisms more vulnerable to extinction?

Small geographic range, specialized habitat or diet, slow reproduction, and sensitivity to environmental change.

How are mass extinctions related to the carbon cycle?

Sea level change, anoxia, volcanism, and bolide impacts all disrupt carbon cycling.

Why is it hard to resolve extinction events from dinosaur fossils?

Dinosaur fossils are rare and often show time lags between last appearance and true extinction.

What is “coherence” in scientific reasoning?

A claim makes sense and explains phenomena, but that alone doesn’t make it factual.

When was the Chicxulub crater discovered?

Linked to the K-T boundary in 1991 off the coast of Mexico.

How powerful was the Chicxulub impact?

~10 km wide asteroid, 58× the speed of sound, 4.5 billion times stronger than a nuclear bomb.

Effects of the Chicxulub impact?

Global tsunamis, fires, CO₂ spike, molten rock rain, superheated winds, and sunlight blocked by dust.

How could humans be causing a “6th Mass Extinction”?

Habitat destruction, climate change, pollution, and overexploitation of species.

What is “commonsense skepticism”?

Healthy suspicion toward claims lacking evidence.

What is “trust in experts” in evaluating claims?

Experts are often sufficient but not necessary for truth; they have access to evidence and data.