2017 Advent Calendar / Advent calendar

Door 21 – Let it snow!

Behind door 21 of the geoadvent, the Geological Society’s Publishing House has some suggestions for some festive reading…





Let it snow, let it snow, let it snow

We’re all dreaming of a white Christmas… unfortunately it looks likely that our Christmas snow has come and gone already in the UK! The last time the UK experienced a white Christmas was in 2009, but proper, snow covered Christmases are rare events.

That wasn’t always the case though – the Earth would have experienced many global white Christmases during the last Snowball Earth event – thought to have ended 635 million years ago.  The whole Earth was a global winter wonderland (probably not as wonderful as you would like to imagine), covered with glacial ice from pole to pole.

As experienced this December in the UK, life struggles to continue with a bit of snow – but during the Neoproterozoic glacial period (Snowball Earth) life was surprisingly active…

Some evidence for this comes from the Neoproterozoic Port Askaig Formation in Scotland and Ireland. The formation contains widespread pyrite within many diamictite beds, suggesting that high levels of microbial sulphate reduction in the subsurface was occurring; the combination of fresh granitic detritus, organic carbon and a source of sulphate was a fertile environment for microbial activity.

Along other records of pyrite-bearing Sturtian diamictite this paints a global picture of microbial activity during Snowball Earth.

If you have a Lyell Collection subscription, you can read more at: Parnell, J. & Boyce, A.J. 2017. Microbial sulphate reduction during Neoproterozoic glaciation, Port Askaig Formation, UK. Journal of the Geological Society, 174, 850, http://jgs.lyellcollection.org/content/174/5/850

There is still much debate as to what was the cause of Snowball Earth, as well as what ended it…however we do know that unlike the film Frozen there was no magical spell to release the Earth from its deep snowball freeze!

Make your own Snowball Earth cookies this Christmas


  • 200g butter
  • 70g icing sugar
  • 1 tsp vanilla extract
  • 370g plain flour, sifted
  • 80g walnuts, pecans (finely chopped) or dessicated coconut


  • Preheat oven to 180°C/350°F/Gas mark 4
  • Soften butter in large bowl
  • Add sifted icing sugar, cream until light
  • Stir in the vanilla
  • Mix in the flour (sifted) and stir in nuts/coconut
  • Shape into mini snowball earths
  • Place on greased baking parchment and bake in a preheated oven for 15 minutes
  • Roll in icing sugar straight out of oven
  • Roll again when they are cool

More Christmas related Lyell Collection reading:

For geologists after some festival journal content this Christmas, here are some suggestions!

Garnets with snowball structures: http://mem.lyellcollection.org/content/48/1/295

On Reindeer (Rudolf’s ancestors):  http://trned.lyellcollection.org/content/5/2/302

Land plant cover in the Devonian – the earliest Christmas trees!: http://sp.lyellcollection.org/content/339/1/59

Mistletoe documenting rapid warming at the Palaeocene – Eocene boundary in North America: http://jgs.lyellcollection.org/content/161/2/173

The formation of gold and other metals in well preserved Vent Chimney structures: http://sp.lyellcollection.org/content/148/1/241

The Bright Angel Shale: http://sp.lyellcollection.org/content/228/1/213

Merry Christmas from all at the Geological Society Publishing House!


Geoadvent challenge update

If you’re playing along, leave a comment below identifying which site from our 20 plate tectonic stories is represented in today’s window! See our website for the full list of sites yesterday’s site was the Alpine Deformation, Albania. 

3 thoughts on “Door 21 – Let it snow!

  1. Pingback: Door 24 – Quiz answers, challenge winners and a very merry Christmas! | Geological Society of London blog

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