article

1. IES Ramón Olleros Curso 2019-2020
Scientific Cultura Irene Santos
ANALYSIS OF A SCIENTIFIC COMMENT BETWEEN DIFFERENT WORK
GROUPS
 DEVELOPING. Analyze the option defended or not by the author.
 Expose the main ideas of your news to the rest of your classmates.
 Next, pay attention to the exposure of the other working groups and take note of
the main ideas.
 Finally, you have to organize all the information collected and prepare a single
scientific report.
 This activity will take place throughout a class session.
WHY DID THE DINOSAURS GO EXTINCT?
Learn about the mass extinction event 66 million years ago and the
evidence for what ended the age of the dinosaurs.
B Y V IC TO R IA J A G G A R D
Abundant fossil bones, teeth, trackways, and other hard evidence have
revealed that Earth was the domain of the dinosaurs for at least 230 million
years. But so far, not a single trace of dinosaur remains has been found in
rocks younger than about 66 million years. At that point, as the Cretaceous
period yielded to the Paleogene, it seems that all nonavian dinosaurs
suddenly ceased to exist.
Along with them went fearsome marine reptiles such as
the mosasaurs, ichthyosaurs, and plesiosaurs, as well as all the flying reptiles
known as pterosaurs. Ancient forests seem to have flamed out across much of
the planet. And while some mammals, birds, small reptiles, fish, and
amphibians survived, diversity among the remaining life-forms dropped
precipitously. In total, this mass extinction event claimed three quarters of life
on Earth.
Piecing together what happened has been a massive effort for paleontologists,
and theories for what killed the dinosaurs and the rest of the planet’s
Cretaceous inhabitants have ranged from the plausible to the downright zany.
For now, two leading ideas are battling it out within the scientific community:
Were dinosaurs victims of interplanetary violence, or more Earthly woes?

2. IES Ramón Olleros Curso 2019-2020
Scientific Cultura Irene Santos
ANALYSIS OF A SCIENTIFIC COMMENT BETWEEN DIFFERENT WORK
GROUPS
 DEVELOPING. Analyze the option defended or not by the author.
 Expose the main ideas of your news to the rest of your classmates.
 Next, pay attention to the exposure of the other working groups and take note of
the main ideas.
 Finally, you have to organize all the information collected and prepare a single
scientific report.
 This activity will take place throughout a class session
DEATH FROM ABOVE
One of the most well-known theories for the death of the dinosaurs is the
Alvarez hypothesis, named after the father-and-son duo Luis and Walter
Alvarez. In 1980, these two scientists proposed the notion that a meteor the
size of a mountain slammed into Earth 66 million years ago, filling the
atmosphere with gas, dust, and debris that drastically altered the climate.
Their key piece of evidence is an oddly high amount of the metal iridium in
what’s known as the Cretaceous-Paleogene, or K-Pg, layer—the geologic
boundary zone that seems to cap any known rock layers containing dinosaur
fossils. Iridium is relatively rare in Earth's crust but is more abundant in stony
meteorites, which led the Alvarezs to conclude that the mass extinction was
caused by an extraterrestrial object. The theory gained even more steam
when scientists were able to link the extinction event to a huge impact crater
along the coast of Mexico’s Yucatán Peninsula. At about 93 miles wide,
the Chicxulub crater seems to be the right size and age to account for the dino
die-off.
In 2016, scientists drilled a rock core inside the underwater part of Chicxulub,
pulling up a sample stretching deep beneath the seabed. This rare peek inside
the guts of the crater showed that the impact would have been powerful
enough to send deadly amounts of vaporized rock and gases into the
atmosphere, and that the effects would have persisted for years. And in 2019,
paleontologists digging in North Dakota found a treasure trove of fossils
extremely close to the K-Pg boundary, essentially capturing the remains of an
entire ecosystem that existed shortly before the mass extinction. Tellingly, the
fossil-bearing layers contain loads of tiny glass bits called tektites—likely blobs
of melted rock kicked up by the impact that solidified in the atmosphere and
then rained down over Earth.

3. IES Ramón Olleros Curso 2019-2020
Scientific Cultura Irene Santos
ANALYSIS OF A SCIENTIFIC COMMENT BETWEEN DIFFERENT WORK
GROUPS
 DEVELOPING. Analyze the option defended or not by the author.
 Expose the main ideas of your news to the rest of your classmates.
 Next, pay attention to the exposure of the other working groups and take note of
the main ideas.
 Finally, you have to organize all the information collected and prepare a single
scientific report.
 This activity will take place throughout a class session.
VOLCANIC FURY
However, other scientists maintain that the evidence for a massive meteor
impact event is inconclusive, and that the more likely culprit may be Earth
itself.
Ancient lava flows in India known as the Deccan Traps also seem to match
nicely in time with the end of the Cretaceous, with massive outpourings of lava
spewing forth between 60 and 65 million years ago. Today, the resulting
volcanic rock covers nearly 200,000 square miles in layers that are in places
more than 6,000 feet thick. Such a vast eruptive event would have choked the
skies with carbon dioxide and other gases that would have dramatically
changed Earth’s climate.
Proponents of this theory point to multiple clues that suggest volcanism is a
better fit. For one, some studies show that Earth’s temperature was changing
even before the proposed impact event. Other research has found evidence
for mass die-offs much earlier than 66 million years ago, with some signs
that dinosaurs in particular were already in a slow decline in the late
Cretaceous. What’s more, volcanic activity is frequent on this planet and is a
plausible culprit for other ancient extinctions, while giant meteor strikes are
much more rare. This all makes sense, supporters say, if ongoing volcanic
eruptions were the root cause of the world-wide K-Pg extinctions.

4. IES Ramón Olleros Curso 2019-2020
Scientific Cultura Irene Santos
ANALYSIS OF A SCIENTIFIC COMMENT BETWEEN DIFFERENT WORK
GROUPS
 DEVELOPING. Analyze the option defended or not by the author.
 Expose the main ideas of your news to the rest of your classmates.
 Next, pay attention to the exposure of the other working groups and take note of
the main ideas.
 Finally, you have to organize all the information collected and prepare a single
scientific report.
 This activity will take place throughout a class session.
WHY NOT BOTH?
Increasingly, scientists trying to unravel this prehistoric mystery are seeing
room for a combination of these ideas. It’s possible the dinosaurs were the
unlucky recipients of a geologic one-two punch, with volcanism weakening
ecosystems enough to make them vulnerable to an incoming meteo
But that notion depends a lot on more precise dating of the Deccan Traps and
the Chicxulub crater. In 2019, two independent studies looked at geochemical
clues from Deccan Traps lava and came to slightly different conclusions, with
one paper suggesting the volcanoes played a supporting role in the dinosaurs’
demise by causing pre-impact declines, and the other saying the eruptions
came after the impact event and may have played only a small role in
ushering along their end.
This debate may rage for years, as scientists dig up new clues and develop
new techniques for understanding the past. But whether space invaders or
loads of lava are to blame, it’s clear that scientists studying the dinosaurs’ last
gasp are revealing vital lessons about the effects of dramatic climate change
on Earth’s inhabitants.

5. IES Ramón Olleros Curso 2019-2020
Scientific Cultura Irene Santos