Mantle Plumes - Its Not That simple! 

I came across THIS ARTICLE and it looks like one I should read. But I suspect it will take me a long time! So rather than take forever to understand it and try to summarise it, I will let you do that! Best of luck! 

a | Schematic cross section through Earth’s interior, depicting the key components of plume generation and upwelling near, above and along the edges of a large low-shear-velocity province (LLSVP) and near the core–mantle boundary. These LLSVPs might contain localized ultra-low velocity zones (ULVZs) and along their edges subducted material may pile up over hundreds of millions of years. b | Schematic cross section of a plume root showing the entrainment of subducted materials, LLSVP and ULVZ components, and possibly core materials at the edge of a LLSVP and centred above an ULVZ (that might be a unique deep mantle locality containing partial melt).

Life - It Gets Everywhere! 

A correspondent brought THIS ARTICLE to my attention. It concerns the fact that life is found in the most unexpected places. Places where there is no apparent energy source. Places mentioned are deep underground in mines and in abyssal sediments.

To cut a (VERY) long story short the energy source is hydrogen. And this is derived from the breakdown of water by radioactivity - electrolysis without electrodes.

Bacteria found deep within a gold mine in South Africa that subsist on hydrogen and sulfate. 

G. Wanger & G. Southam

The article goes into some detail about how this was discovered and proved to be a viable energy source. - well worth reading.

Book Review - The Greywacke 

Recently I bought "The Greywacke" (ISBN 978 1 78816 377 4, eISBN 978 1 78283 626 1) written by Nick Davidson, an amateur geologist. And it is rather good!

It tells the story of how two friends, Sedgwick and Murchison, mapped the geology of Wales and the Welsh Borderland, disagreed, compromised and then disagreed completely. Later Charles Lapworth proved them both wrong. 

It does not sound a riveting read but the people involved are compelling characters and they all did remarkable work.

Sedgwick was geology professor (with a divinity and mathematics degree) at Cambridge and worked on the Cambrian. He was good but slow and full of doubts. Murchison was a retired army officer and worked on the Silurian. He was fast and did not have a doubt in his life - certainly not about his abilities! He published quickly and extensively and could not help himself encroaching on Sedgwick's territory.

While still cooperating, Sedgwick and Murchison sorted out the rocks between the Silurian and the Carboniferous and called it the Devonian, rubbishing De la Beche on the way.

Murchison, having, to his own satisfaction, coloured most of Wales Silurian, moved on to do the same to the Southern Uplands and most of the Northern Highlands. 

Also he was invited to tour Russia - twice - named the Permian and co-wrote a two volume book "The Geology of Russia in Europe and the Ural Mountains". Murchison's volume weighed in at 13 pounds! It stretched from Primary rocks in the west to Permian and higher in the east - an undisturbed sequence. Strangely, Murchison could not find any Cambrian!

By this time he was the most distinguished geologist in the world and not averse to being crowned "King of Siluria" Later he was appointed Director of the Geological Survey. 

But it could not last. Geology was changing. Nemesis came in the form of Charles Lapworth. He was a schoolteacher from Oxfordshire who came to Galashiels to teach English and art. He was intrigued by the local rocks which had recently been mapped by the survey as being Silurian and 26,000 feet thick. 

Murchison had mapped Russia in a few months; Lapworth mapped tiny Dobb' Linn over five or six summers, camped for months at a time in a shepherds hut. The result was the Silurian was reduced from 26,000 feet to 300 and a major unconformity was put in the middle of it! Eventually the Ordovician was defined. 

It took a long time for the Survey to admit the existence of the Ordovician. Not many years ago the Survey would label rock units according to the geological period - all the Carboniferous ones began with a d, c for the Old Red, a for the Cambrian and b for the Silurian. The Ordovician was in there usually with a b!

The geological establishment, especially the Survey, regarded Lapworth as an amateur. After correcting them in the Southern Uplands he moved onto Wales, found more major unconformities, proved the Ordovician and the headed for the North West Highlands where, once more the Survey and Murchison were proved to be fundamentally wrong. Geikie, Murchison's successor as head of the Survey sent his top team to look at the area and they agreed with Lapworth! The first paper confirming Lapworth's findings did not mention Lapworth.

As you can see I found this book fascinating and well written. As far as I can tell the geology is correct. It must be - Dave Green is one of the people who helped him!

The Latest Ice Age 

I joined the Geol Soc Western Zoom lecture yesterday evening and it was fascinating. The amount of knowledge of the latest ice age is fantastic.

THIS WEB PAGE is a good starting point. The interactive map on THIS PAGE summarises the current knowledge - zoom in to see ever greater detail.

Glaciers are not Sterile. 

Jemma Wadham, a professor at Bristol, has written a book, Ice Rivers, (ISBN-10 : 0241467683, ISBN-13 : 978-0241467688) which she introduces in THIS ARTICLE.

She has had a life long love of glaciers and seems to have visited all of them!

She writes about the microbes living in and beneath glaciers. Many live on the soil and other organic stuff below the ice, producing methane - the methanogens. But there are others which consume the methane - the methanotrophs. 

Fast flowing rivers emerging from melting glaciers are super-saturated with methane. No one knows how much methane is trapped in glaciers, some in solid  form as methane hydrate.

What is on the Menu? 

Here is a new word for you - pabulite! Defines as a fossilized meal which never entered the digestive tract. It is different from regurgitalites - I am sure you can work out what that is!

All this comes from an ARTICLE recommended to me by a correspondent. The article is based on an ACADEMIC PAPER in a Swiss Journal.

The source of all these neologisms is a fossil extracted from the Posidonia Shale, part of the Toarcian (early Jurassic) of Germany. It consists of a belemnite which has captured a decapod crustacean. And there is damage to the belemnite suggesting it was predated by some vertebrate. The Early Jurassic shark Hybodus hauffianus is suggested. The shark seems to have dropped its prey before ingesting it - and so we get a pabulite!

The academic paper is very interesting - lots to get your teeth into.

Volcanism and Creativity 

A frequent correspondent sent me THIS LINK. Watch it with your loudspeakers turned on.

The current eruption in Iceland has spawned a myriad of videos. This is one of the best.

Iron and Ice Ages 

My "water in the mantle" super correspondent has also sent me THIS LINK. It looks at the connection between low CO₂ in the atmosphere and iron bearing dust in the oceans.

The idea is that the Southern Ocean has lots of the nutrients for biomass but biomass is low. The constraining factor is iron. In ice ages the lack of cover allows dust  - including iron - to be blown out to sea where it allows the formation of  biomass. Some of this sinks and therefore removes CO₂ from the atmosphere.

A fine theory, but how to prove it? More biomass getting to the ocean depths would provide food for deep-sea microorganisms. These would consume oxygen to process the extra food and therefore, in ice ages bottom waters would be oxygen poor. This has been found to be true with modern geochemical measurements.

Figure 1 | The anti-correlated data that inspired the iron hypothesis. a, Measurements of air bubbles trapped in cores drilled from the Antarctic ice sheet show that atmospheric levels of carbon dioxide were significantly lower during the coldest periods (shaded regions) than during modern times (data from ref. 16; CO2 concentrations are shown in parts per million by volume; p.p.m.v.). b, The ice-core records also reveal that more iron was transported to the Southern Ocean in wind-blown dust during the coldest periods than during warmer times (data from ref. 17; iron flux is measured in micrograms per square metre per year). In 1990, Martin2 hypothesized that the increased levels of iron in the Southern Ocean during the coldest periods fertilized the growth of photosynthetic microorganisms in the surface Southern Ocean, which therefore produced more biomass from CO2. This, in turn, would have increased the strength of the biological pump, a mechanism that sequesters some of the biomass (and the carbon within it) in the deep ocean. Martin proposed that the stronger biological pump explains why so much atmospheric CO2 is drawn into the ocean during cold times.

Is All the Water in the Oceans Just a Minor Part of Earth's Water? 

Another super correspondent (not the Mars and teeth one) gave me the link to THIS ARTICLE. It describes the minerals likely to be found in the transition between the upper and lower mantle - wadsleyite and ringwoodite. These do not ordinarily exist on the earth's surface. They can, theoretically, hold water. The speed of seismic waves through them is affected by their water content. The author thought that this proved that the transition zone was water-rich, but refrained from publishing as to suggest such a thing was somewhat radical.

Then a crystal of ringwoodite was found inside a Brazilian diamond formed in the transition zone and it contained 1% water! The amounts of ringwoodite are huge, therefore the amount of water must be huge - twice the volume of the oceans! (No one has quantified this in terms of Olympic sized swimming pools - yet!)

Implications of this are that there must be molten material in the transition zone - some seismic work confirms this.

Further work suggests more water above and below the transition zone.

The article then discusses the presence of water and suggest it is essential for plate tectonics and life on earth.

Geophysicists are finding more and more water deep under Earth’s surface, especially in the transition zone, which is full of waterbearing minerals. (Credit: Jay Smith)

Geol Soc Mars Lecture 

The correspondent who suggested the Mars video below and the bit about fossil teeth also suggested THIS LECTURE and it is great - 0ne hour and fifteen minutes of great video and knowledge about Mars.

Excellent Mars Video 

A correspondent brought THIS to my attention. Sit back and watch, the commentary is rather annoying but everything else is great!

Sharks Teeth No Longer the Ancestral Tooth 

It was a bit of a surprise to me but I found out today that sharks teeth were, until now, considered the sort of tooth from which all other teeth, including our own, were derived. It had not been at the forefront of my thought, I must admit, but now I know that RECENT RESEARCH has shown that tooth patterns evolved independently many times. 

It all started with some nicely preserved acanthodian (shark precursors) jaws. Intense study of these using intense X-rays (sorry) showed that they had two types of teeth - teeth in rows and teeth in whorls. Teeth evolved in many different ways. So the shark model is not useful for dentists looking at human dental problems.

Digital models of acanthodian tooth rows (left) and tooth whorl (right) Martin Rücklin, Naturalis Biodiversity Center

Study Mars in Iceland 

You have all enjoyed the fire fountains in Iceland - see the PREVIOUS POST, but now for some serious geology - or rather geology of Mars!

A correspondent brought THIS ARTICLE to my attention. It uses the current Icelandic eruption as an illustration of what happened on Mars in the distant past. (Although some of the people quoted rather hope for a new Martian eruption!)

The video in the article is well worth looking at with some beautiful imagery from Mars - and some good stuff from Iceland! A smaller version of the video is embedded below.

There is ice and lava in Iceland and where the two meet microbes are found. There is ice and there was lava on Mars - are there microbes to be found? Read the article and view the video and join in the speculation!

 Icelandic Fire Fountain

Icelandic Volcano - the Gift that Keeps on giving! Below is a short, silent, video showing a fire fountain at the Icelandic Volcano, currently erupting. Or you can see it HERE. This was recorded Wednesday morning.

This activity has continued and on Saturday morning we got the following. You can also see it HERE

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