Remember last lesson we talked about how Earth is 4.5 billion years old, and we mankind have only called it home for 140,000 years?
Well, now let’s take a walk through this planet’s history. We will take a look at Continental drift and how it has helped shape present day Earth. We will meet some of the awesome creatures that have called this planet home and look at how, despite five mass extinction events, life has always “found a way” (Jurassic Park Quote)
Let’s first start with a quick activity
Can you tell us something you are curious about and something you are not curious about?
Perhaps you are curious to learn about human rights but you are not curious to learn about politics? Just because you are not curious about something does not mean it’s not important. We all have different skills and passions, this is what makes us unique and this is something that should always be respected and nurtured.
Is history important?
Here’s what we think;
History provides us with solutions to many of the problems of the present. It allows us to reflect and learn from those before us.
It is a tool that we can draw inspiration from. History teaches us that things can change and from this perhaps we can find courage. When pressed against the present it can become so easy to feel overwhelmed. However, when we delve into history we can draw inspiration from those before us. Those that made decisions, created movements and inventions whose waves are still felt today.
It also gives us a sense of place, and where we have come from. Connecting us to every person and creature, everything living thing that has shared this remarkable planet with us.
geologic time scale
The geologic time scale (GTS) is a system of chronological dating that relates geological strata (stratigraphy) to time. It is used by geologists, paleontologists, and other Earth scientists to describe the timing and relationships of events that have occurred during Earth's history.
The various time scales are divided into geological eras, and eras into geological periods. The chart below illustrates this. We’ve also added some icons for some of the topics we are going to cover today, to better help you imagine the time scales we are referring to.
Plate tectonics is the theory that Earth's outer shell is divided into several plates that glide over the mantle (the rocky inner layer above the core). According the the World Atlas there are 9 major plates. These constantly shifting plates have formed mountains ranges, created oceans, formed supercontinents and ultimately created Earth as we know it today.
the five mass extinctions
In the history of this planet we know of five mass extinction events, when the majority of life on Earth disappeared in the “blink of a geologic eye” (Joe Hanson).
Dovician - Silurian (450 million years ago)
The second largest of the five major extinction events, saw an estimate of 85% of all Ordovician species disappear. With global cooling and falling sea levels.
Late Devonian (365 million years ago)
The late Devonian eliminated 70 to 80% of all animal species, caused by several stresses such as; lack of oxygen, rapid global warming or cooling and meteorite or comic impacts.
End Permian (250 million years ago)
This event wiped out 96% of Earths species. Nicknamed the ‘Great Dying’. Less than 5 percent of the animal species in the seas survived. Possibly caused by an asteroid that hit just below Australia.
Triassic - Jurassic (200 million years ago)
This event saw the demise of 76% of all marine and terrestrial species. The dinosaurs, pterosaurs, crocodiles, turtles, mammals, and fishes were little affected by the transition. This event still remains a matter of considerable debate. Many scientists predict that this event was caused by climate change and rising sea levels resulting from the sudden release of large amounts of carbon dioxide.
Cretaceous - Paleogene (66 million years ago)
Known at the K-T extinction global extinction event responsible for eliminating approximately 80 percent of all species of animals. The extermination of the dinosaurs has been a puzzle to paleontologists, geologists, and biologists for two centuries, however rocks of that age contain traces of an asteroid that struck Earth, generating catastrophic events.
Looking at these 5 mass extinction events, can you identify any patterns?
Truth is there isn’t a pattern, we cannot possibly predict when the next mass extinction event will occur. Except see the little question mark on number 6?…
The Sixth Extinction
Anthropogenically: of, relating to, or resulting from the influence of human beings on nature.
Defaunation: Used to denote the loss of both species and populations of wildlife.
While deforestation is a term that is now readily recognised, and influential in focusing scientific, and general public attention on biodiversity issues, (particularly as remote sensing technology provides rigorous quantitative information and compelling images of the magnitude, rapidity, and extent of patterns of deforestation). Defaunation is a term that remains a largely cryptic phenomenon.
“In less than two generations of humans, the populations of vertebrate animals have dropped by 52% between 1970 and 2010”
Meet elasmosaurus (EE-LAZMO-SORE-us)
A poster lizard which still holds a somewhat mythical status is the ‘Loch Ness Monster” which bares remarkable resemblance to the elasmosaurus. Elasmosaurus lived during the Cretaceous period. At close to 15.2 metres and up to three tonnes, the Elasmosaurus was one of the biggest plesiosaurs of the Mesozoic Era. Elasmosaurus had the longest neck of any plesiosaur yet identified, about half the length of its entire body and supported by a whopping 71 vertebrae!
Elasmosaurs, although beautifully adapted to aquatic life, were still reptiles, and thus had lungs rather than gills, meaning they had to surface to breath. Despite many depictions showing this majestic reptile holding it's neck elegantly out of the water, palaeontologists have concluded that, given the enormous size and weight of its neck, Elasmosaurus was incapable of holding anything more than its tiny head above the water.