Saturday, 12 September 2020

Where Does the Carbon in Diamonds Come From?

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)




Friday, 4 September 2020

Hibernation is Not New

 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.


Tuesday, 1 September 2020

Methane Outgassing in Siberia

 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.


Saturday, 29 August 2020

Tuatara Genome Revealed

Tuatara Genome Revealed 

A correspondent has brought THIS ARTICLE to my notice. It tells of how the genetic material of the tuatara was collected, in collaboration with the iconic species Maori guardians. Without their cooperation the material could not have been gathered. 

The genome is 50% larger than the human genome and is one of the largest ever published. One purpose was to reconstruct the creatures evolutionary tree.

A tuatara in New Zealand. Credit: Pete Oxford/NPL


And here is its evolutionary tree - the simple version.
 Refining the evolutionary tree for reptiles, birds and mammals. This phylogenetic tree includes six branches: mammals and five branches within a clade called sauropsids, which comprises reptiles and birds. One of these, the Rhynchocephalia, has only one living member, the tuatara. Gemmell and colleagues date the divergence of the Rhynchocephalia from the Squamata to about 250 million years (Myr) ago


And here is the more complex version, taken from THE ORIGINAL PAPER.

a, The tuatara, (S. punctatus) is the sole survivor of the order Rhynchocephalia. b, c, The rhynchocephalians appear to have originated in the early Mesozoic period (about 250–240 million years ago (Ma)) and were common, speciose and globally distributed for much of that era. The geographical range of the rhynchocephalians progressively contracted after the Early Jurassic epoch (about 200–175 Ma); the most recent fossil record outside of New Zealand is from Argentina in the Late Cretaceous epoch (about 70 Ma). c, The last bastions of the rhynchocephalians are 32 islands off the coast of New Zealand, which have recently been augmented by the establishment of about 10 new island or mainland sanctuary populations using translocations. The current global population is estimated to be around 100,000 individuals. Rhynchocephalian and tuatara fossil localities are redrawn and adapted from ref. 1 with permission, and incorporate data from ref. 2. In the global distribution map (c, top); triangle = Triassic; square = Jurassic; circle = Cretaceous; and diamond = Palaeocene. In the map of the New Zealand distribution (c, bottom); asterisk = Miocene; cross = Pleistocene; circle = Holocene; blue triangle = extant population; and orange triangle = population investigated in this study. Scale bar, 200 km. Photograph credit, F. Lanting.

 The papers are interesting as they give an insight into modern biology. 

Down to Earth Extra - September 2020

 

DOWN TO EARTH EXTRA - September 2020


The latest edition of Down to Earth Extra is HERE.

And you can read it below.


Wednesday, 19 August 2020

Zoom Geological Webinars from Cardiff University

 Zoom Geological Webinars from Cardiff University

The School of Earth and Ocean Sciences at Cardiff University is organising a series of Zoom webinars, held at 5PM on Wednesdays.

You can read all about it HERE. Instructions on how to join the webinar are on the site.

I have missed the first couple of seminars but the full list is as follows:- 


Dave Green's Geostudies Programme

 Dave Green's Geostudies Programme

In these uncertain coronavirus times, Dave Green has boldly gone and put together a programme for the rest of this year and next. Let us hope it can go ahead as planned! Dave can be contacted HERE.


Dave writes:-

Saturday, 15 August 2020

Landslides and the Railways

Landslides and the Railways 

There has been much on the airwaves and in the papers about the dangers climate change induced landslides pose for the railways. A correspondent sent me THIS which shows that the same concerns have worried people in the railway industry, over the years. 

The paper covers the methods used to determine where conditions are suitable for landslides to occur. It does not present its results in sufficient detail to see whether the place where the recent derailment near Stonehaven was classed in its hierarchy of landslide possibilities. That was not its purpose.

But Network Rail and the BGS do have that information. This will show whether the area was a risk. But it will not tell you that a landslide will occur on a particular day. I suspect that predicting landslides is similar to predicting earthquakes!


Tuesday, 11 August 2020

Ocean-going Crinoids

Ocean-going Crinoids 

Those well known fossils, crinoids, are often found attached to, what are now, small pieces of coal. Originally these were pieces of driftwood.

Fossil crinoid attached to coal

William Buckland (and very possibly, Mary Anning) suggested that the crinoids had been attached to pieces of driftwood while alive, living suspended underneath it. For many years this was thought to be an impossibility - the weight of the crinoids would have caused the driftwood logs to sink.

But the author of THIS ARTICLE, and his co-workers, using many different sorts of advanced techniques, has worked out that crinoids do indeed hang suspended underneath the driftwood but clustered towards one end of it. Such a log could drift for ten to twenty years.

So now we know! The original article is HERE

Artists impression of a crinoid raft.

Friday, 7 August 2020

What was Tanystropheus?

What was Tanystropheus? 

A correspondent has brought THIS ARTICLE to my attention. And the answer, according to the researchers, is an aquatic creature. And not one I would like to meet in a non-fossilised form - it was active 242m years ago. It was up to 6 metres long, with a long stiff neck. Fortunately its head, and teeth were small.

The researchers conclude that there were two species of Tanystropheus - the larger hydroides and the smaller longobardicus. The newspaper article is based on THIS ARTICLE which has all the details.

An artist’s impression of Tanystropheus, fossils of which were first found around 150 years ago. Photograph: Emma Finley-Jacob/University of Zurich/Current Biology

Thursday, 6 August 2020

Geology from your Sofa

Geology from your Sofa

In this time of enforced isolation the Geologists' Association, (the GA) has produced the "Geology from your Sofa" web page. You can find it HERE. There is a tremendous amount of stuff to read and look at.

Well worth clicking on!



Short Field Course 2020 from Dave Green

Short Field Course 2020 from Dave Green

Dave Green is suggesting a short field course of 3 excursions. I received his advertisement on the day of the first one so there are 2 awaiting your presence. 

The advertisement and details are HERE. Or you can read it below.


GEOSUFFOLK TIMES

GEOSUFFOLK TIMES

THIS has come across my desk and is a pleasant read. It is also reproduced below.


Down to Earth Extra - August 2020

DOWN TO EARTH EXTRA - August 2020


The latest edition is a 2 page introduction to the 40 page Down to Earth magazine which is not being printed - unless you ask Chris Darmon for a specially printed one.

The 2 page Extra is HERE.

The 40 page Magazine is HERE.

If you prefer smaller downloads they are HERE and HERE

Or you can read Down to Earth Extra below.

And Down to Earth Magazine below that.





Thursday, 30 July 2020

Where Did Stonehenge's Sarsens Come From?

Where Did Stonehenge's Sarsens Come From?

I came across THIS ARTICLE and then a correspondent sent me the link to the ORIGINAL SOURCE. Stonehenge is a never ending subject. These articles are well worth looking at.

Sarsen stones are post-glacial silcretes - quartz sandstones with a quartz cement and are - almost - 100% silica. The authors discuss the place of origin of the sarsens. Almost all of them have an identical trace element composition and they use this to identify a place with an identical chemical signature. 

This is West Wood, 25 km to the north of Stonehenge. As some of the sarsens weigh about 30 tonnes, this would not have been a trivial undertaking!



Wednesday, 22 July 2020

The East African Rift System and Landslides

The East African Rift System and Landslides

When I think of the East African Rift System, landslides are not the first thing on my mind. THIS ARTICLE from one of my most prolific sources, Earth-logs, may make me change my mind. 

The "Rise to the Rift" was much mentioned many years ago. We now know what causes it - bulging of the continental crust resulting both from its unloading by thinning along the rifts and the buoyancy conferred by high heat flow in the mantle beneath - but the result is landslides.

The East African Rift System (Credit: P.C. Neupane, M.Sc thesis 2011; Fig. 1)

There is enhanced erosion, both into the rift and outwards, especially onto the the Indian Ocean continental shelf. Recent oil exploration work, offshore Tanzania, has illuminated this.

In particular it has shown the presence of a vast submarine landslide, called (intriguingly) the Mafia mega-slide. It is thought that it was caused by a large earthquake and would have caused a large tsunami.

Seismic reflection profile parallel to the Tanzanian coastline with the Mafia mega-slide highlighted in green (Credit: Maselli et al. 2020; Fig. 5)

You can find details of this work HERE. The main thrust of the paper is using the records of offshore sedimentation to fix the dates of the rifting and to note the dangers of future submarine landslides.

Tuesday, 21 July 2020

Active Volcanoes on Venus?

Active Volcanoes on Venus?

THIS ARTICLE in a newspaper tells of an interpretation of ring structures on Venus, found using radar, as being volcanic in origin. They call them coronae structures - the trench surrounding the peaks. The researchers think the coronae are fields of lava flows and major faults.

They suggest that such structures can only be produced by volcanic activity. And many of them were active in the last few million years.

Two coronae on the surface of Venus which are formed when hot material from deep inside the planet rises through the mantle. The black line shows a gap in the imaging data. Photograph: Laurent Montesi/Reuters

The newspaper article is based on a paper in Nature Geoscience, which you can read HERE