WHAT HAPPENED TO
THE DINOSAURS
Tapouh Alyssa-Grade 9
Who first developed the idea that there was
an asteroid impact that killed the dinosaurs?

The idea that an asteroid impact killed the dinosaurs was first developed by
Luis Alvarez and his son Walter Alvarez, a father-and-son team of scientists, in
1980.

They proposed the hypothesis after noticing that 66-million-year-old clays
around the globe contained far more of the rare metal iridium than other
rocks, suggesting that the element was delivered by an extraterrestrial
object.

The iridium metal relatively rare in Earth's crust but is more abundant in
stony meteorites, which led to the conclusion that the mass extinction of the
dinosaurs was caused by an extraterrestrial object, as evidenced by the high
amount of iridium found in the geological boundary zone that marks the
extinction event.
When did the Father-and-son
team put forward this
theory?

In 1980, Nobel Prize-winning
physicist Luis Alvarez and his
geologist son Walter Alvarez
published a theory that a historic
layer of iridium-rich clay was caused
by a large asteroid colliding with
Earth. This is known as the Alvarez
hypothesis.

They proposed this theory based on
the discovery of elevated levels of
iridium in the K-Pg boundary around
the globe and the identification of a
massive crater, known as the
Chicxulub crater, in Mexico, which
was believed to be the impact site.
The K-Pg Boundary
The K-Pg boundary, also known as the
Cretaceous-Paleogene boundary, is a
geological signature that marks the end
of the Cretaceous period and the
beginning of the Paleogene period,
approximately 66 million years ago. It is
a thin layer of sediment found
throughout the world in marine and
terrestrial rocks, which shows unusually
high levels of the metal iridium, more
common in asteroids than in the Earth's
crust. The K-Pg boundary is associated
with the Cretaceous-Paleogene
extinction event, a mass extinction
that destroyed a majority of the world's
Mesozoic species, including all
dinosaurs except for birds. The high
levels of iridium found in the boundary
clay suggest that the extinction was
caused by the impact of a massive
comet or asteroid
What was the evidence that Luis
and Walter Alvarez put forward
their theory?

The evidence that Luis and Walter
Alvarez put forward to support their
theory that an asteroid impact killed
the dinosaurs includes the discovery
of elevated levels of iridium in the KPg boundary around the globe, the
identification of a massive crater,
known as the Chicxulub crater, in
Mexico, which was believed to be the
impact site, and the presence of
shocked quartz and microtektites
along with the iridium and soot in the
Cretaceous/Tertiary boundary, which
could only have been produced in the
heat and violence of a titanic impact.
The Alvarezes also found that the
iridium, which was in a very even,
widespread distribution, was the
result of a giant asteroid that hit the
Earth around 65 million years ago.