- Dinosaurs lived on Earth for over 165 million years from the late Triassic period until the end of the Cretaceous period 65 million years ago. They varied greatly in size and appearance. - Extinction occurs when a species can no longer adapt to environmental changes, leading to their death. A popular theory is that an asteroid impact caused the mass extinction that killed the dinosaurs. However, some evidence challenges this and suggests massive volcanic eruptions may have been responsible. - The document discusses and provides evidence for both the asteroid impact theory and volcanic eruption theory for the cause of the dinosaur extinction. While the asteroid theory was widely accepted, newer evidence is increasingly supporting the volcanic eruption theory as well.

1. Case study on
dinosaurs
INTRODUCTION
What are dinosaurs?
:-Dinosaurs were one of the most dominant animals
ever to have lived on our Earth. They lived on the
Earth for (a)over 165 million years; from the late
Triassicperiod (about 230 million years ago) until
the end of the Cretaceousperiod (65 million years
ago). Dinosaur is translated from the Greek
deino and sauros meaning terrible and lizard which
describes exactly what most dinosaurs looked like.
However (a) Dinosaurs have varied in size, with
some known to have grown to a massive 15 meters
tall and others to be only the size of a
chicken. Dinosaurs were very, very different from
one another. For example some were big and some
were small, some walked on two legs and some

2. walked on four, and some were armor-plated, some
had crests, horns or even spikes.
What does extinction mean?
:- Extinction is the complete disappearance of a
species. Extinction usually occurs if a specie on
Earth cannot adapt quickly enough to a serious
change in the environment, which causes death.
What are the facts that support this theory?
:-Luis Alvarez and Walter Alvarez found the layer
of iridium, that they later based their Asteroid
Impact Theory on, in Italy but layers like this have
been found all over the world.
The reason why the layer was first noticed to be
unusual was because of the vast quantities it was
discovered in. Iridium is a very rare element and for
it to be found in such large amounts there must have
been a momentous and significant event in which
this huge amount of iridium was unearthed. Alvarez
then researched as to where this iridium could have

3. come from. The main place where iridium is known
to exist is in outer space, another place is in the core
of the Earth. The only part of the Earths crust where
measurable amounts of iridium can be found is in
volcanic areas. The Alvarezes decided that the most
likely theory from the evidence they had collected
was that an Asteroid hit the Earth sending up the
dust from the Earths surfaced where the asteroid had
landed but also any debris from outer space that was
on the asteroid, for example iridium. An asteroid
between 4 and 9 miles long would have had enough
impact on the Earth and carry enough iridium to
explain the mass extinction and the layer of iridium
in Italy.
Another fact that backs up the theory of Luis and
Walter Alvarez is that special ‘shocked quartz’ that
was found in the layer of iridium.

4. Asteroid theory
What is the background information of this
theory?
:- Asteroids are minor planets, especially those of
the inner Solar System. The larger ones have also
been called planetoids. These terms have
historically been applied to any astronomical object
orbiting the Sun that did not show the disc of a
planet and was not observed to have the
characteristics of an active comet. As minor planets
in the outer Solar System were discovered and found
to have volatile-based surfaces that resemble those
of comets, they were often distinguished from
asteroids of the asteroid belt. In this article, the term
"asteroid" refers to the minor planets of the inner
Solar System including those co-orbital with Jupiter.
There are millions of asteroids, many thought to be
the shattered remnants of planetesimals, bodies
within the young Sun's solar nebula that never grew
large enough to become planets. The large majority
of known asteroids orbit in the asteroid belt between
the orbits of Mars and Jupiter, or are co-orbital with
Jupiter (the Jupiter trojans). However, other orbital

5. families exist with significant populations, including
the near-Earth objects. Individual asteroids are
classified by their characteristic spectra, with the
majority falling into three main groups: C-type, M-
type, and S-type. These were named after and are
generally identified with carbon-rich, metallic, and
silicate (stony) compositions, respectively. The size
of asteroids varies greatly; the largest is almost
1,000 km (625 mi) across.
What are the facts that support this theory?
:-There was no escaping the extinction event for
the dinosaurs, not even at the planet’s poles,
according to new research that supports the theory of
an asteroid strike being the culprit.
A study of 6,000 Antarctic fossils suggests dinosaurs
there lived no longer than those in the rest of the
world.
The reason for the mass prehistoric extinction is still
debated – however, the researchers say their new
finding supports the hypothesis that the dinosaurs
were wiped out by the impact of an enormous

6. asteroid, rather than environmental changes due to
volcanic activity.
Previously, many believed the ordeal was far enough
away from the world’s poles that dinosaurs in those
areas survived longer than others. It was thought that
polar dinosaurs might be better equipped to deal
with dramatic changes in environment, due to their
experience through months of darkness and low food
supply.
But new research – and one of the biggest fossil
studies of its kind – refutes these theories.
An international team of researchers studied a
collection of 6,000 marine fossils, lifted from
Seymour Island on the Antarctic Peninsula, dating
between 69 and 65 million years old.
What are the facts that challenge this theory?
:- The crater, discovered in 1978 in northern
Yucutan and measuring about 180 kilometers (112
miles) in diameter, records a massive extra-
terrestrial impact.

7. When spherules from the impact were found just
below the Cretaceous-Tertiary (K-T) boundary, it
was quickly identified as the "smoking gun"
responsible for the mass extinction event that took
place 65 million years ago.
It was this event which saw the demise of dinosaurs,
along with countless other plant and animal species.
However, a number of scientists have since
disagreed with this interpretation.
The newest research, led by Gerta Keller of
Princeton University in New Jersey, and Thierry
Adatte of the University of Lausanne, Switzerland,
uses evidence from Mexico to suggest that the
Chicxulub impact predates the K-T boundary by as
much as 300,000 years.
"Keller and colleagues continue to amass detailed
stratigraphic information supporting new thinking
about the Chicxulub impact, and the mass extinction
at the end of the Cretaceous," says H. Richard Lane,
program director in the National Science Foundation
(NSF)'s Division of Earth Sciences, which funded
the research. "The two may not be linked after all."

8. Volcanic theory
What is the background information of this
theory?
:- A popular theory has it that, at least in certain
types of volcanos, eruptions occur when molten rock
known as magma gushes up from deep inside the
earth via narrow jets known as mantle plumes. But a
new study of seismic data has identified one very big
hole in the theory:
Mantle plumes don't exist.
"Mantle plumes have never had a sound physical or
logical basis," study co-author Dr. Don L. Anderson,
professor emeritus of geophysics at Caltech in
Pasadena, California, said in a written statement
released by the university. "They are akin to
Rudyard Kipling's 'Just So Stories,' a reference to the
British author's tales offering silly explanations for
how giraffes and other animals got their peculiar
anatomies."

9. What are the facts that support this theory?
:- Huge volcanic eruptions that belched sulfur into
the air for around 10,000 years could have killed the
dinosaurs, according to new evidence unearthed by
geologists.
Evidence is accumulating that it wasn't an asteroid
that did the beasts in, but volcanoes – the first real
challenge the extinction theory has met in three
decades.
A combination of studies on dinosaur fossils,
magnetic signatures in rocks and the timing of the
disappearance of different species suggest it was
volcanoes, not an asteroid, that caused the dinosaurs'
extinction.
"We're discovering ... amazingly large flows,
amazingly short time scales and amazing volcanic
(eruptions)," said Vincent Courtillot of the
University of Paris, who is is presenting new
evidence for the volcano theory this week at the
American Geophysical Union conference here.

10. What are the facts that challenge this theory?
:- Scientists have found even more evidence that
volcanism, not a space rock, may be the culprit
behind the dinosaurs' demise.
The first well-supported theory for what wiped out
all large dinosaurs involved a space rock that created
the Chicxulub crater in Mexico’s Yucatan Peninsula.
But climate change and volcanism have been
suggested in recent decades, too. A set of new
studies further shifts the blame away from the
impact and toward volcanism, a position that
geologist Gerta Keller of Princeton University has
taken in recent years.
Keller and others now say more about the life-
extinguishing work of a massive series of sulfur
dioxide-spewing volcanic eruptions that occurred in
what is now India at the time of the dinosaur-
destroying K-T mass extinction (the shorthand given
to the Cretaceous-Tertiary extinction). The asteroid-
impact "theory is now facing perhaps it's most
serious challenge from the Deccan volcanism and
perhaps the Chicxulub impact itself," Keller said

11. today during a news conference at the annual
meeting of the American Geophysical Society in San
Francisco.
The K-T extinction ended the dinosaurs' reign on
Earth and caused the extinction of 70 percent of life
on the planet at the time.
Thank you