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How Dinosaurs
Went ExtinctBy Daniel He
Table of Contents
The Mesozoic Era 1
The Triassic Period 3
The Jurassic Period 4
The Cretaceous Period 5
The End of the Dinosaurs 6
Asteroid Impact 7
Volcanism 8
Ice Age 9
Climate Change 10
Competition with Other Species 11
Other Theories 12
The Mesozoic EraThe Age of Reptiles
The Mesozoic is an era that started at 252.2 million years ago to 65.5
million years ago, and is composed of the Triassic Period, the Jurassic Period,
and the Cretaceous Period.
The Mesozoic was a place of giants, with dinosaurs ruling the world. They
first evolved from Archosaurs into dinosaurs during the Triassic Period, turned
larger and more diverse in the Jurassic and Cretaceous periods, but got wiped
out by the K-Pg extinction and the end of the Cretaceous period.
But dinosaurs weren’t the only successful species in the Mesozoic, there
were pterosaurs roaming the sky, and pliosaurs ruled the seas (they also
evolved from archosaurs), and perhaps one of the only ones that no one
expected to survive, the first mammals also evolved during the Mesozoic, as
well as ichthyosaur (Triassic), turtles (late Triassic), flowering plants (Jurassic)
and birds (Cretaceous).
The most common dinosaurs of each period
There were some big changes to Earth during the Mesozoic. At the start of
the era, there were no seasons, and there was only one supercontinent,
Pangaea. Since most of that continent was far from water, the center of the
continent was mostly lifeless deserts that were hot enough to cook most
creatures alive. But the Earth was changing, and the gradual tilt of the Earth
created the seasons, and the continent also started to split up into their
formation today, and the scorching wasteland of Pangaea started to blossom
with life.
The Ancient Supercontinent of Pangaea, in the Jurassic, when all the landmasses were joined together
The Triassic PeriodDawn of a New Era
The Triassic started off as a hot, lifeless desert, having recently suffered
the Permian Extinction. Even the few survivors of the crisis were disappearing
quickly. But, as always, with death comes life, and when the old species dies,
the new takes over.
In the supercontinent of Pangaea, some of the species have survived, and
evolved. A new species, a two legged reptile called an Eoraptor, the first
dinosaur, diverged from archosaurs, and started to repopulate the Earth. They
evolved, diversified, and began to dominate the planet.
The planet started to go through changes, and the biggest change was
the splitting of Pangaea. Eventually the continents split far enough to house a
new sea, one that would become the northern Atlantic Ocean and the Gulf of
Mexico. With more water inland, there are more plants, with more plants
there are more herbivore dinosaurs, with more prey, there are more
carnivores. A new water source doesn’t only benefit fish and amphibians; it
helps land animals, too.
A scene from the Triassic
The Jurassic PeriodA Green World
The Earth during the Jurassic was truly a green world. There were Jungles
all across the two supercontinents Laurasia and Gondwana, as well as ferns
and conifers. Pangaea had split in half, with Laurasia to the north, and
Gondwana to the south.
The sauropods began to get huge, so more predators started to hunt in
groups. The predators also got larger, though, and they are starting to take the
shape that many large carnivore dinosaurs would take: short front leg, strong
back leg, large and powerful jaws, and their overall size increased as well.
An ocean predator, liopleurodon, evolved from archosaurs, and started to rule
the sea. The first mammals also appeared first in the Triassic. A couple million
years later, A new species evolved from the liopleurodon, the elasmosaurus,
and their skull got smaller, but their neck got longer as well, and they have a
total of 71 neck vertebrae. This gives them an advantage for that they can
attack a whole school of fish, and while their huge body stays invisible, their
neck rise up and can easily feed without much notice.
The Jurassic dinosaurs
The Cretaceous PeriodFinal Glory
The Cretaceous is the last period in the Mesozoic Era. The tyrannosaurus
rex, the triceratops, pachycephalosaurus, and spinosaurus (largest carnivorous
dinosaur of all times, 16 – 18 meters) all appeared during that period.
Flowering plants covered the planet, as well as many trees and ferns.
Other than the dinosaurs, the Earth was a place much like today, with most of
the continents near where they are today, and most of the plants seen today
other than deciduous trees. The mammals were also evolving into a shape
much like today’s rat with longer front leg. They lived in burrows to avoid
predators, although they would soon take over Earth, they were no match for
the dinosaurs.
But then something that not even enormous creatures like dinosaurs
could stop happened. The event killed 75% or more of all the species on Earth,
including all of the large reptiles, and most of the marine animals.
The Cretaceous Period
The End Of the DinosaursA Tragic Event
65.5 million years ago, in a catastrophic event called the K-Pg Extinction,
the dinosaurs were destroyed forever. This event ended the 185 million years
long rule of the dinosaurs, and the age of the reptiles. Scientists have always
been puzzled by how that happened, and these are some of the most popular
theories:
Asteroid Impact
Volcanism
Ice Age
Climate Change
Competition With Other Species
I’m also going to tell you about my theory and some other theories.
The extreme volcanism theory
Asteroid Impact
A lot of people believe that asteroids killed the dinosaurs. Because there has
been lots of evidence:
Molten rock:
Molten rock found all over the world at the Cretaceous – Paleogene boundary
indicates that a huge amount of energy suddenly melted and through these
rock very far away.
Craters:
There were craters all around the world, and a lot of them is believed to be
the one that was created by the K-Pg asteroid. But it was the discovery of the
crater in the Gulf of Mexico in 1978 that proves that the theory is very possible
Rare Metal:
A rare metal called iridium is found scattered around Earth at the K-Pg
boundary. Iridium is very rare in the Earth’s crust, but common on asteroids.
An artist’s impression of an asteroid impact scene
Volcanism
Volcanoes can also explain how the dinosaurs went extinct, but there was
also evidence of an asteroid impact, so that caused someone to think about a
combined theory: The Deccan Traps wiped out most dinosaurs, and the
asteroid cleaned up the rest.
The Deccan trays were formed by a flood basalt eruption about 66 million
years ago, and it could have made the air toxic.
Or it could have been the geographical movement that made other
volcanoes that did the job.
An example of a flood basalt eruption
Ice Age
Ice ages could also have killed the dinosaurs. There has been some fossils
to support this theory. Cold water planktons indicates that there was
something that suddenly made the water cold.
But an ice age does not explain evidence of the other things from that
time, so that cause a combined theory. Since an ice age small enough to not
leave much evidence probably couldn’t have killed the dinosaurs, it could have
been a volcano or an asteroid that helped with the job.
A small scale ice age
Climate Change
This is also a possible theory because there was definitely climate change
at that point, because there weren’t any seasons before. But tilting of the
Earth cause there to be seasons, and studies indicate that this happened
around the time dinosaurs went extinct.
A climate change event could have made a lot of species not used to the
new climate, and therefore it would explain why dinosaurs weren’t the only
ones that went extinct.
The four seasons
Competition with Other Animals
This is a plausible theory because scientists found that the dinosaur
population was already decreasing before the extinction. Although this might
not be the result of competition, it could have.
Mammals could have eaten the dinosaur’s eggs, spread disease, and a
number of things that all could have led to the extinction of the dinosaurs.
A mammal eating an egg, possibly a dinosaur’s
Other Theories
There are other theories for how the dinosaurs went extinct, but it’s very
unlikely that they are true:
Epidemics
A Planet Overrun By Males
Cosmic Rays
The Dinosaurs Just Faded Away Into Extinction
Dinosaurs Got So Big That They Crushed Themselves
Dinosaur Fart (containing methane) Killed Themselves
But don’t even think about believing in them. They are totally false.
Cosmic rays