By Stephen Monahan

Demise of the Dinosaurs

Demise of Dinosaurs Discovery

Discovered by Luis and his son Walter Alvarez in 1980Proposed Asteroid

Theory

What was believed before Asteroid TheoryLack of evidence of

other opposing theories, made volcanic theory the given causeCorrelates to

knowledge about other mass extinctions

How the discovery was made?

A piece of limestoneFrom "great dying“

Neutron activation analysis (NAA) by Asaro and MichelAllowed for precise

measurementsDiscovered twenty-

five time increase of iridium

Issues with Asteroid TheoryUnlikely that so many

species killed in short period of time

Single event of the asteroid hitting the earth or a succession of events caused the extinction

Time is often evidence to the contrary

Scientific Resistance to Asteroid TheoryGerta Keller studies of

many rock formationsFossil remains to date

surrounding geologic features

El Penon, 52 species discovered in the layer below asteroid layer found in layer above

Concluded that volcanoes was more likely

Further Research on Asteroid TheoryIn 1991, scientists found a

impact craterNew data from debris suggest

extinction and impact happened within 33,000 years period

A small layer of sediment around the world contains a lot of iridium

Collection of 45 scientists from different fields Went through each possible

cause

Applications of Asteroid Theory and Modern View

The impact from the asteroid made subsurface rocks unstable by disturbing them

Dust sent into the atmosphere from the impact

Significant variations in the climate

Global wildfires Modern View is not

unanimous but mostly to Asteroid Theory

THE END