Ice Ages come and Go

16 Feb 2020

At https://archaeologynewsnetwork.blogspot.com/2020/02/scientists-show-sola... ... scientists show solar system processes control the carbon cycle - throughout Earth's history (or at least that part of it in which humans have existed). Below is an image from the Jurasic coast of Dorset, the so called 'Belemnite Mud Member' - which is geological speak for a mudstone sedimentary formation that can be seen in the sea cliffs of the Jurassic coast. It seems a similar geological horizon exists in Wales, also with abundant fossils of marine belemnites ...

   ... the image is said to show paced variations of tghe sediment composition similar to the deposit in Wales studied by the researchers (from Trinity College in Dublin). The claim is that periodic changes in the  shape of the Earth's orbit around the Sun (see image below). The claim is that periodic changes in the shape of Earth's orbit were responsible for changes in the carbon cycle and global climate during the Triassic and Jurassic mass extinction events. In addition, massive volcanic activity released large amounts of greenhouse gases which resulted in perturbations in the global carbon cycle etc. ....

   ... which is one way to bury the idea of catastrophe and read a sedimentary layer as extremely longwinded rather than a quick and rapid laying down of mud. The we have the volcanic activity.

At https://archaeologynewsnetwork.blogspot.com/2020/02/coincidences-influen... ... coincidences influence the onset and ending of Ice Ages - according to Danish scientist POeter Ditlevsen of the Univerisity of Copenhagen. Whilst the Milanokovitch Theory is neat (see the image above) providing us with periodisation in glaciations, it is a theory based on mathematics, making use of small changes in solar radiation. The orbit of the Earth has an elliptical shape, or circuit, and the Earth also seems to wobble (slightly). These small changes in the amount of light and heat reaching the poles is a 40,000 years cycle that is perceived as forcing climate change such as the Ice Ages and Interglacial events. However, according to Ditlevsen, the Milankovitch theory doesn't explain everything ... simply because the periodicities of Ice Ages is not as precise as the mathematics. Why? Coincidences, it would seem, play a role. Is that sublime - or plumbing the sink.