ch 14-3 what killed the dinosaurs

What period of extinction is one of the five largest in the history of life

• end Cretaceous

  • 2nd most devastating mass extinction

  • end of the dinos

  • sharp decrease in species diversy

what period was more devastating to global biodiversity?

• end Permian extinction

what do extinctions hit?

• both land and sea fauna

who was affected by the end Cretaceous extinction?

• non-avian dinosaurs, pterosaurs, marine reptiles, ammonites, and rudist bivalves all died out (75% of all species)

• 80-90% marine species lost

• many plant species

what survived the end Cretaceous extinction?

• avian dinosaurs (birds), crocodiles, mammals, amphibians, fish

what do we have good evidence of for what caused of End cretaceous extinction?

• m

What are the three proposed causes of the End-Cretaceous extinction?

• Asteroid impact, massive volcanic eruptions, and global marine regression.

What impact event is associated with the End-Cretaceous extinction?

• The Chicxulub asteroid impact.

What volcanic event may have contributed to the End-Cretaceous extinction?

• The Deccan Traps eruptions in India.

What is global marine regression?

• A worldwide drop in sea level.

What is the strongest evidence for the cause of the End-Cretaceous extinction?

• Evidence for a large asteroid impact, including the Chicxulub crater and a global iridium layer.

what is the most researched evidence for end of cretaceous extinction?

• meteorite or asteroid impact causing widespread climatic change

What evidence supports the asteroid-impact theory for the End-Cretaceous extinction?

• A worldwide iridium layer, shocked quartz crystals, and tektites found at the extinction boundary.

Why is the iridium layer important evidence for an asteroid impact?

• Iridium is rare on Earth but abundant in meteorites, suggesting extraterrestrial material was deposited globally.

What are shocked quartz crystals?

• Quartz crystals deformed by the extreme pressures of a large impact.

What are tektites?

• Droplets of melted rock ejected from an impact site that later cooled and solidified.

What are the three main pieces of evidence for the asteroid-impact theory?

• Iridium layer

• Shocked quartz

• Tektites

what is a key piece of evidence for the asteroid impact theory?

• ancient crater caused by bull eye collision

• should’ve caused so much dust clouds that block light and end photosynthesis and collapse food chain

cause of cretaceous extinction: Mexico?

• well defined concentric rings

• end of C period

• peak ring structure

  • form by rocks behaving like fluid

  • drop hit pond

  • rocks deep forced up and collapse outward tom form multi-ring basin

How large was the asteroid that caused the End-Cretaceous extinction?

• About 10–15 km wide, roughly twice the height of Mount Everest.

How fast was the Chicxulub asteroid traveling when it struck Earth?

• About 20 km/s, or roughly 60 times the speed of sound.

Why did the Chicxulub impact have global effects?

• The asteroid was extremely large and moving at very high speed, releasing enormous amounts of energy and causing worldwide climate change.

  • hit at seep 45-60° angle and released massive amounts of energy

How powerful was the Chicxulub asteroid impact?

• It released energy equivalent to about 4.5 billion atomic bombs.

Why did the Chicxulub impact cause a mass extinction?

• Its enormous energy caused global climate changes, wildfires, and blocked sunlight worldwide.

Chicxulub impact energy?

• ≈ 4.5 billion atomic bombs.

Global Iridium layer

• evidence supporting asteroid-impact theory

  • end of C-era by rocky clay

  • platinum group metal very rare in Earth crust but abundant in Asteroids

  • global layers indicates of extra terrestrial source

What evidence suggests widespread fires occurred after the Chicxulub impact?

• Soot layers associated with the global iridium layer indicate widespread fires following the impact.

What do soot layers at the K–Pg boundary indicate?

• Widespread wildfires after the asteroid impact.

What are tektites?

• Natural glass formed when rocks melt and are ejected during a meteorite or asteroid impact.

How are tektites formed?

• By melting rock during an impact event.

Why are tektites evidence for the asteroid-impact theory?

• They are produced by the extreme heat generated during a large impact.

What is shocked quartz?

• Quartz that contains shock lamellae (cross-hatched stress lines) formed by the extreme pressure of an asteroid or meteorite impact.

What are shock lamellae?

• Cross-hatched stress lines in quartz crystals produced by an impact.

Why is shocked quartz evidence for an asteroid impact?

• It forms only under extremely high pressures, such as those generated during a large impact.

What are tsunamiites?

• Sedimentary deposits left behind by massive tsunamis.

Why are tsunamiites evidence for the Chicxulub impact?

• They indicate enormous tsunami activity that occurred at the end of the Cretaceous.

What do tsunami deposits (tsunamiites) indicate?

• Large-scale tsunami activity caused by the asteroid impact.

Where are tsunami deposits from the Chicxulub impact most common?

• Around the Chicxulub impact site in Mexico.

what are the meteorite impacts effects?

• blocking of sun

• acid rain

• cascading effects lasting long periods of time

how did meteorite impacts block the sun?

• 60x mass of meteorite ejected into atm. (rock, dust, sulfur, and soot into stratosphere)

  • 10 km diameter

• heat of impact caused massive wildfires

• temporarily halted photosynthesis

• months of global cooling

how did meteorite impacts cause acid rain?

• vaporized rock and atmospheric gases mixing → sulfuric and nitric acid

  • into atm. that would combine with water

  • ocean acidification and damage to terrestrial