Down to Earth Extra - October 2020

DOWN TO EARTH EXTRA - October 2020

The latest edition of Down to Earth Extra is HERE.

And you can read it below.

 Viruses can be Fossilised

Professor Maurice Tucker has sent me a PAPER ON VIRUSES which he recently published in "Geology Today" which is very interesting - in several ways! 

We are all suffering, directly or indirectly, from the coronavirus. If you want a good introduction to what a virus is, Professor Tuckers paper is a good place to start. 

The numbers of viruses in almost anything are phenomenal. A normal size person may have tens of trillions of bacteria in their body, but there may be ten viruses for every bacteria. But they are much smaller. You may have 200 grams of bacteria in your body, but the much larger numbers of viruses may weigh less than 10 grams.

The only way to see a virus is with an electron microscope. So your hand lens will not be of much use to find a fossilised virus. The paper has electron microscope pictures of modern viruses being fossilised. It seems that they can become nuclei for minerals to form around, destroying their shape.

Transmission Electron Microscope (TEM) images from a biofilm showing silica nanoparticles with cores of virus-like particles and solid silica nanoparticles within a bacterial cell (a) and close-up (b), from a hot spring in China. (Images courtesy of Xiaotong Peng, Chinese Academy of Sciences, Sanya, China.)

There is lots of good stuff in the article, including a discussion on the origin of viruses and of life itself. A rewarding read!

 Another Mass Extinction!

Mike Benton of Bristol University wrote THIS ARTICLE last week. So, rather belatedly, it appears here.

The extinction event was rather difficult to recognise. We knew of 5 such events - now we have 6. It happened 233million years ago, in the middle of the Triassic, and is called the Carnian Pluvial Episode (CPE) and seems to have killed off as many species as the asteroid at the end of the Cretaceous.

The ending of the tetrapods left a space which the dinosaurs filled for the next 165million years.

A timeline of mass extinction events. D. Bonadonna/MUSE, Trento, Author provided

The CPE was first noticed in Europe, to which, it was thought to be restricted. Then its time correlation with the eruption of the Wrangellia basalts was noticed. I had not noticed the concept of Wrangellia until now, but it seems to be one of the terranes welded onto the west coast of North America.

The Wrangellian eruptions led to acid rain - it is a Pluvial event! - which acidified the oceans and cleaned off the land surface. When the eruptions stopped so did the rain but temperatures remained high - dinosaur weather!

The effects in the oceans were great. Before the CPE carbonates in the oceans came from microbes. After it was coral reefs and plankton.

Where Does the Carbon in Diamonds Come From? 

this week I found THIS ARTICLE on the Earth-logs blog. It is based on THIS PAPER. It was thought that the carbon came from subducted sedimentary rocks. Then we thought of the basalts in the oceanic crust. Their reaction with aqueous fluids results in carbonates.

Current research uses the isotopic chemistry of carbon and nitrogen in the diamonds and the tiny silicate minerals included in them. Most of these are garnets. From the studies the depth of formation can be indicated and this can help determine the carbon source.

And it seems that the oceanic basalts are the favoured source.

But VERY deep diamonds - formed below 660km - may be different. The isotopes suggest that the carbon source is within the mantle and ultimately the stellar dust that accreted to form the earth. But at that depth the carbon is incorporated in metals and carbides. The authors suggest that subducted slabs, reaching that depth, release watery fluids which mobilise the trapped carbon and allow the formation of diamond.

Diamond crystal containing a garnet and other inclusions (Credit: Stephen Richardson, University of Cape Town, South Africa)

 Hibernation is Not New

A correspondent brought THIS ARTICLE to my attention.

Lystrosaurus is the creature which survived the end-Permian mass extinction. In the Triassic they were found all over Gondwanaland. The specimens used in this study came from what is now Antarctica and South Africa. In Triassic times Antarctica was within the Antarctic Circle, South Africa outside it. 

Lystrosaurus is characterised by having tusks, which like elephants tusks, grow throughout their lives. And they have growth rings. The South African specimens have regularly spaced rings, the Antarctic ones have the same but also closely-spaced, thick rings.

a A cross-section of Antarctic specimen UWBM 118025 with a “hibernation zone” highlighted at a higher magnification. Scale bars = 1000 μm. b Well-preserved regular incremental growth marks from the South African specimen UWBM 118028, lacking “hibernation zones”. Arrows denote individual lines with an average spacing of 16–20 μm. Scale bar = 100 μm.

The authors argue that this indicates the Antarctic creatures were hibernating - or something very like it. Which is not really surprising but nice to have some evidence for it.

The original article is HERE.

 Methane Outgassing in Siberia

By chance I came across THIS STORY in the Siberian Times. it seems, that with global warming methane is being released by the permafrost, often with spectacular results.

 The new funnel filmed from air by the team of Yamal-based TV station. Picture from July 2020 by Vesti Yamal. Note the figures for scale.

The other pictures in the article are equally spectacular. 

This is a rather worrying development. Methane is a more powerful greenhouse gas than carbon dioxide and there is believed to be vast quantities of it captured in the permafrost. If it continues to be released it will trigger a vicious circle.