Dinosaur Extinction – Providing Information Sheets for Schools
Helping Primary School Children with Their Dinosaur Studies
Team members at Everything Dinosaur visit lots of school to undertake dinosaur workshops to help with teaching science as part of the UK’s national curriculum. During our sessions with children aged from 4 years and upwards we get asked some amazing questions by the eager, budding palaeontologists. We answer the questions as best we can but sometimes we are unable to deal with a specific enquiry during the teaching session itself, but we always follow up and send out further information and other resources to help the teaching staff with extension activities.
After all, taking dinosaurs into a school means that the school children are very excited and keen to learn all about these prehistoric animals as well as to demonstrate applied knowledge.
One of the questions we do get asked a lot concerns the extinction of the Dinosauria, typically we get asked “How and why did the dinosaurs go extinct”.
To help teachers, Everything Dinosaur has prepared a number of useful information sheets covering different aspects of palaeontology and the study of dinosaurs.
How and why did the Dinosaurs go Extinct? Typical information sheet prepared for Key Stage 1/2
The dinosaurs went extinct 65 million years ago, at what we call the end of the Cretaceous (CREE-TAY-SHOUS); this marked the end of the Age of Reptiles and the start of the Age of Mammals. Not only did the dinosaurs die out but also all the flying reptiles and the large marine reptiles went extinct as well. Many different types of fish, shelled animals such as the ammonites (AM-MON-NIGHTS) became extinct along with many small animals such as certain kinds of plankton that lived in the sea and a large number of plants.
Something like sixty percent of all life on Earth died out, this type of event is called a mass extinction and these have happened from time to time throughout the history of our planet.
Scientists cannot be certain as to what exactly happened to the dinosaurs, there have been a lot of theories put forward to explain why the dinosaurs, other animals and plants went extinct. Each theory has its own set of supporters, scientists that have looked at the evidence in fossils and rocks and come to a conclusion as to what might have happened.
We have listed some of the theories put forward, presenting evidence to support each theory and provided some other information presented by scientists who oppose this point of view.
In your class, weigh up the evidence look at the information presented and see if you can decide what wiped out the dinosaurs.
Your turn to be scientists…
Theory 1 – Death from Outer Space
If you look at a picture of the moon in a book you will see that it is covered in craters. These have been caused by asteroids and meteorites crashing into the moon over millions and millions of years. The moon has no weather, no atmosphere, so these craters are not eroded away, they are a permanent reminder that there are lots of chunks of rock and ice whizzing around in space.
Our planet has an atmosphere, it has weather, if an asteroid crashed into Earth, depending on the size of the rock, it could cause a lot of damage, but the crater would eventually get weathered away and any evidence of the impact would be eroded. The Earth gets hit by lots of debris from space all the time, most of these rocks are very small and burn up in our atmosphere, they form shooting stars that sometimes you can see on a clear night.
However, every once in a while a huge lump of rock crashes into our planet and some scientists think that at least one huge meteorite or asteroid crashed into the Earth around sixty-five million years ago and this led to the demise of the dinosaurs.
Asteroid Impact Theory – Extinction of the Dinosaurs
If a big enough piece of space rock crashed into the Earth then shock waves would be sent around the world, earthquakes would be caused and if the rock hit the sea, massive tidal waves would flood the surrounding land. The impact would vaporise much of the rock and the ground where it hit. Huge clouds of smoke, dust and rock would be thrown up into the atmosphere. The rock would be molten and it would fall down to earth, as showers of red-hot material, causing forest fires that would add even more smoke to the atmosphere.
The fine particles thrown up and the smoke could spread across the whole planet, disrupting weather patterns and ocean currents, the sun could be blocked out and the Earth could enter into a period of world-wide winter, killing off what vegetation remained. A big enough impact would have resulted in an environmental disaster and this could have led to the death of many different animals and plants.
Depending on where the meteorite or asteroid hit, the damage done to the Earth could be made much worse if the place where the impact occurred had lots of rock with sulphur in them. If the impact caused lots of sulphur to get thrown up into the atmosphere then this would have combined with other materials in the air and formed acid rain (sulphuric acid).
Acid rain would have destroyed much of the vegetation and damaged the delicate communities of plankton in the sea which in turn would have led to the collapse of food chains and the demise of lots of animals and plants.
Death from Outer Space – The Evidence
1. The K-T Boundary (Rare Elements found in sixty-five million year old rocks)
In some parts of the world, the rocks that were laid down at the end of the Cretaceous are separated from the rocks that make up the first deposits of the Tertiary (TER-SHERRY), the Age of Mammals, by a thin layer of red-grey clay. Scientists have tested the clay deposits (it is called the K-T boundary) and they have discovered that it contains high levels of rare Earth elements such as Iridium. This element is scarce on Earth but is found in meteorites, could this be evidence of a meteorite impact sixty-five million years ago?
A Clay Deposit Marks the End of the Age of Dinosaurs
Picture credit: Open University/Everything Dinosaur
2. The Crater
In 1990, evidence of a huge crater 200 kilometres wide was found off the coast of Mexico. The asteroid or meteorite that caused this crater must have been at least 10 kilometres wide. Little evidence of the impact can be found on land but a study of the seabed in the Gulf of Mexico and the rock layers in the area indicates that at around sixty-five million years ago a huge body from outer space crashed into the Earth.
A Disaster for Life on Earth
Such an event would have been disastrous for life on Earth but not all scientists agree with this theory. Why did the turtles in the sea survive but no other marine reptiles? How did birds survive and most mammal species? Some scientists state that only the very smallest land animals were able to survive, a lot of dinosaurs were small, they do not seem to have made it through to the Age of Mammals. Crocodiles did not go extinct, they have armour on their bodies like turtles and tortoises perhaps this is how they survived, but many dinosaurs like Anklylosaurus (AN-KIE-LOW-SORE-US) had armour as well but these animals went extinct.
Theory 2 – Global Climate Change
Although the age of dinosaurs ended suddenly, in geological timescales suddenly can mean as long as 100,000 years or more. It is not possible to tell from rocks whether the events that caused the death of the dinosaurs took place over a few years or over a much longer time period.
Could gradual global climate change have caused the extinction of the dinosaurs?
When scientists look at the fossils found in rocks aged between 70-75 million years ago, they find lots of different types of dinosaur. When scientists examine rocks from some parts of the world that are dated between 70-65 million years ago they find fewer types of dinosaur. This might indicate that the dinosaurs were slowly dying out. Scientists studying dinosaur fossils in rocks from 74 million years ago have found the fossils of over thirty different types of dinosaur, in studies of rocks from 67 million years ago, only about nineteen different types of dinosaur are found.
Extinction of the Dinosaurs
Between 70-65 million years ago a rising current of hot, molten rock began bubbling up from the Earth under western India. This led to huge volcanic eruptions in the region. These eruptions lasted for millions of years. So much lava and molten rock was thrown out in volcanic explosions and lava flows that scientists estimate that enough material was ejected to cover 1.5 million square kilometres.
Huge amounts of carbon dioxide gas would have been sent up into the atmosphere. Lots of carbon dioxide in the atmosphere affects the climate and weather patterns just as we are seeing today.
Climate change could have resulted in the deaths of many different kinds of plants and animals; they were unable to cope with their changing environment.
Global Climate Change – The Evidence
1. The Gradual Decline in the Number of Certain Types of Fossil Found
Studies of tiny fossils in rocks close to the South Pole indicate that at the end of the Cretaceous period there was a gradual but steady decline in marine life. Survival was getting difficult for animals and plants living in the polar regions, this indicates that slowly and surely the environment was changing and plants and animals were struggling to cope.
2. The Deccan Traps
Much of India today is covered in layers of lava now turned into basalt rock. These are the remains of the huge volcanic eruptions that occurred at the end of the Cretaceous. In some parts, these volcanic layers of rock are nearly 5,000 metres deep. This is volcanic activity on a huge scale.
So much carbon dioxide was pumped into the atmosphere it led to global climate change. Even life in the sea would have been badly affected. More carbon dioxide in the atmosphere would have become dissolved in the seas this would lead to an increase in acidity levels in oceans. Many types of plankton cannot survive in water that is slightly acidic; this would have caused the death of the plankton and the collapse of whole marine food chains.
The amount of carbon dioxide pumped out into the atmosphere would have been many times what we are experiencing today. We know that many animals and plants are endangered by global warming at present, so the animals and plants around at the end of the Cretaceous would also have been threatened with extinction.
There are lots of other theories around; did aliens hunt the dinosaurs to extinction? Did biting insects spread diseases amongst the dinosaurs and this led to their demise? Were all the plant-eating dinosaurs killed off by the spread of poisonous flowering plants and this also led to the death of the meat-eaters too?
Everything Dinosaur has put two of the most likely theories to your class; you must weigh up the evidence and decide what you think happened?
1). Did the mass extinction event take place very suddenly caused by the impact and consequences of a huge meteorite or asteroid hitting the Earth?
2). Did the mass extinction event take place gradually as a result of global climate change?
3). Perhaps the extinction of the dinosaurs was caused by a combination of factors. Global climate change had caused many types of plant and animal to decline and a big impact from outer space finally saw many of them go extinct.
Over to you and your classmates…
Although we have over simplified this subject area, the idea behind the information we have provided is for teachers to use this as part of their lesson plans and scheme of work preparation for a dinosaur themed term topic.
To learn more about the range of dinosaur themed toys and gifts stocked by Everything Dinosaur: Dinosaur Themed Gifts and Toys.