TellUs: "The Earth's Story" Series, Asteroid Strikes & Homo Sapiens

The Earth’s Story Series: Cenozoic Era

Leading on from my previous blog about the Mesozoic era aka the ‘middle era’ of deep time, todays blog is focusing on the Cenozoic era. This era is commonly referred to as the ‘modern era’ and you’ll see why as you continue reading! Check out my previous Earth Story Series if you haven’t already. We are nearing the end of the Earth’s geological time history now, leading into the modern day, meaning this series is near a close. So if you’re interested in how the Earth has evolved to where it is now, then do check that out!

Cenozoic Era

As we draw closer to the present day, the finishing line of our journey through deep time, we begin 65 million years ago in the Cenozoic era, often referred to as the ‘modern era’. 

In true Earth style this era starts off with a bang… however quite literally this time! Another mass extinction occurs this was caused, in part at least, by a large asteroid strike that forms a crater off of the Yucatan Peninsula in Mexico. The impact crater created is named the Chicxulub crater, as its centre is located near the town of Chicxulub, Mexico. Nowadays this crater is buried under the Yucatan Peninsula. As well as this incident, massive volcanic eruptions were taking place in parts of India. This mass extinction affected dinosaurs in particular and it is accepted near enough worldwide to have been what caused their extinction. Consequently the subsequent evolution of mammals then leads them to become the dominant land vertebrates.

For much of this modern era the climate is warmer than what you would see today. The main reason being is that the levels of carbon dioxide in the atmosphere is higher. However around about halfway through this era these levels fall and the climate begins to cool. The Antarctic moves away from Australasia and is surrounded for the first time by the deep waters of the Southern Ocean, allowing ice sheets to develop. Following on the Indian subcontinent has completed its journey north to connect into Asia, giving rise to the Himalayan mountains. The geography of the Earth is now similar to what it looks like today. Then approximately 1.8 million years ago we enter the Quaternary period in which the Earth cools rapidly and enters a new ice age - a series of long periods of glacial cold interrupted by short periods of comparative warmth, known as interglacials. 

Ever since the last mass extinction 65 million years ago (mentioned at the start), the diversity of life has been increasing and is as rich as ever before! This blog would be endless if we went into detail about all this rich diversity. So instead we will focus on one particular species, with the appearance of the early members of the hominidae, the family of which humans belong! The human species, Homo sapiens, emerge from Africa about 200,000 years ago. Approximately 11,000 years ago we enter the Holocene period. It takes in the last interglacial of the current ice age, during which human agriculture, nations and cities developed. 

This then continues until the modern day however the impact of humanity’s presence is creating a human footprint which is starting to majorly effect the Earth. Some experts say it is so significant of an impact that it is changing the processes of deep time. My next blog will be focusing on this new Anthropocene geological time. So make sure you subscribe to get notified when I upload and don’t miss out!

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