The end of the world is nigh

20th March 2025- Earth’s Great Extinction Events – Shaun Livesey

Shaun suggested that this is local and global history, and the oldest history you can get!

“Deep time” is measured in hundreds of millions of years referring to geological and cosmic events that far exceed human history.  He showed a slide of a 24-hour clock where 1^st life begins at 8 (1/3^rd); 1^st extinction event at 10; 1^st plants at 18; 1^st humanoids at 48secs; 1^st homo sapiens at 4 secs and civilisation at 1 sec!!

The Earth is 4.5 billion Years old, so it was too hot to sustain any life form, the 1^st evidence of which was around 3.5 billion yrs ago. Occurring in thermal vents and warm pools in the form of primitive Cyanobacteria who obtain their energy from non-organic chemicals (oxygenic photosynthesis) Pt.1 This caused sulphurous compound that laid down hydrochloric acid. Pt.2 Oxygen catastrophe- new and very reactive, oxidising the oceans, producing ‘rust rain’. Pt.3 2.5 to 2.1 billion years ago cells evolved that coped with O2, antioxidants which had an effect on the atmosphere creating the 1^st global ice age, although it produced an ozone layer which protects from UV

 Mass extinction events (not total extinction) are usually dramatic events caused by meteors hitting the earth, it is estimated that 99% of species are extinct, life hangs on somewhere!  Another Chart followed identifying the top 5 extinction events: end-Ordovician (445 MYA {Million Years Ago} impact on 85% of marine species- trilobites, brachiopods); end-Devonian (360 MYA) ammonites, most corals, global cooling-Sijan ring meteor in Sweden, anoric swing fossils; end- Permian (250 MYA) The Great Dying affecting 95% marine species and 70% terrestrial species, even insects; end – Triassic (201MYA) 50% of species including many reptiles (ichthyosaurus) causing many big volcanic eruptions and asteroid impact and end- Cretaceous (65MYA) An asteroid 6 miles wide hit the Yucatan Peninsula at 46 000 mph causing iridium to form across the globe and major volcanic activity, acid oceans no Sun(the event that killed off the dinosaurs). Anthropocene extinction Pt.1 caused by human activity pre-industrial, hunting ‘mega Fauna’. Pt.2 1700 to present: best land occupied for farming, deforestation, over fishing, hunting/poaching big game and burning fossil fuels.  Life will survive, but the ‘good times’ are over. In the UK sea levels will rise by 70m by 2100

Questions followed about the impact UK’s efforts have in comparison with China (2 new coal fired Power stations/week) and India, what caused the end of the dodo, all answered by Shaun. Stuart gave the vote of thanks saying how fascinating he found it all the way through, putting in perspective human impact, but took on board Shaun’s message “Don’t worry, sleep well”. He was impressed by the journey Shaun had taken us with his excellent delivery, his humour that enhanced what could have been a dry subject, but most of all his enthusiasm for the subject that shone through and the members joined him in a stirring round of applause.                          AR