Thursday, 22 April 2021

Deep Sea Volcanoes - What Do We Know - Not Much

Deep Sea Volcanoes - What Do We Know - Not Much

A correspondent and I both spotted THIS ARTICLE today, and we both thought it was worth putting on the blog.

Most of the Earth's volcanic activity occurs under the sea but this was not realised until the 1950's and even today very little is known about it - mid-ocean ridges and black smokers. 

It was thought that deep-sea eruptions were rather boring. In particular explosive eruptions would not happen as the water pressure would prevent the possibility of steam. But now the presence of tephra tells us that explosive eruptions do occur - caused by expanding bubbles of carbon dioxide.

Megaplumes of hydrothermal fluids in the ocean have been detected, up to and over 100 cubic kilometres in volume. This is a lot of Olympic sized swimming pools!

Mapping of volcanic ash deposits suggests that the ash dispersal is caused by high energy plumes. The amounts of energy required are huge and the plumes form quickly over seafloor eruptions and are formed, not from the energy of a lava flow - these would be too small - but by the expulsion of hot fluids (hotter than 300℃) from the sea bed. The eruption of the lava drives the expulsion of a much larger volume of  hydrothermal fluid.

The authors propose that a side effect of these plumes is the dispersal of life across the Earth. And as life may have started in the extremophile communities, they may have been an influence on the origin of life on Earth.

Friday, 16 April 2021

Did India Speed-Up to Create the Himalayas? - NO!

Did India Speed-Up to Create the Himalayas? - NO! 

A correspondent has sent me THIS LINK (and its ACADEMIC PAPER FOUNDATION) for which I am very grateful.

It was long thought India, on its journey from the edge of Africa to the site of its crashing into Eurasia, to create the Himalayas, sped up. The reason for the speed-up was that it "slid off" the dome caused by the rising of the Reunion mantle plume.

This seemed too simple for the authors of the academic paper. Their studies showed that there was a speed-up, not only in India's travels but, at the same time, the separations of Africa / Antarctica, Africa / South America and Antarctica / South America all sped up.

The time period was at the boundary between the Cretaceous and the Tertiary - the chrons C28-C29 to the aficionados of the period. They conclude that this period was actually 70% longer than previously thought.

And the result is that Plate Tectonics, once again follows the rules.

Ubiquitous 67 Ma acceleration in model divergence rates for five plate pairs in Indo-Atlantic circuit (see text for model references). Light-gray bars—magnetic reversal time scale of Gradstein et al. (2012), where C25n–C32n.2—magnetic chrons. Red hatching—Deccan volcanism. 

Sunday, 11 April 2021

Another Icelandic Volcano Video

Another Icelandic Volcano Video 

I came across THIS VIDEO on a photographic site. It shows some of the most spectacular video I have seen. It was shot almost entirely using drones. You will not be surprised that the photographer ended up with a somewhat melted drone! Watch the video on the largest screen you can.

Tuesday, 6 April 2021

Tungsten Isotopes and the Beginning of Plate Tectonics

Tungsten Isotopes and the Beginning of Plate Tectonics 

Super correspondent also sent the link to THIS ARTICLE. It describes, in a remarkably simple way, the use of tungsten isotope tungsten-182 to determine the start of plate tectonics about 3.2 billion years ago. Give or take 100 million years.

Tungsten-182 is formed from the radio-active decay of hafnium-182 within 60 million years of the formation of the solar system. Find a lot of tungsten-182 compared to the other tungsten isotopes and the rock concerned had not been churned by subduction.

So find rocks to which nothing much has happened in the last few billion years. That, of course, means the Yilgarn of Western Australia where nothing much geological happens.

All this sounds rather straightforward, but actually doing it is not easy - neither in the bush or in the laboratory. The article tells the story well.

Collecting specimens in the Yilgarn.

An Unusual Volcano - and Why it Matters

An Unusual Volcano - and Why it Matters 

A super correspondent brought THIS (and the next item) to my notice - thank you very much!!!

In January 2015, WEGA had a lecture by Dr. James Hammond, one of the geologists mentioned in the video, about the Mt Paektu volcano on the borders of China and North Korea. I remember his lecture as being very interesting. Obviously more work has been done on the data and the video goes into a lot of detail concerning the fate of the Pacific Plate as it descends into the mantle.

The video goes into what could be abstruse minutia but does it in an informative manner. Well worth watching.

If you spot something which you think should be on the blog, send me the link and you too could be a super correspondent!

Saturday, 3 April 2021

Jurassic Coast Geology Cruises

Jurassic Coast Geology Cruises 

In July 2007 WEGA took part in a Geology Cruise from Exmouth to (almost) Lyme Regis and it was a great success aided by magnificent weather and an expert commentary from Richard Scrivener, at that time, the Geological Survey's man in Exeter.

And recently I came across a reference which told me that these cruises are continuing. I do not know who is doing the commentary (if there is one) and the exact route but you can book for the 29th of June and the 13th September HERE.

The scenery is lovely - not all the rocks are Jurassic!


Our cruise in 2007

Friday, 2 April 2021

First Animals at the Oxford University Museum of Natural History

First Animals at the Oxford University Museum of Natural History 

Some of you must know about THIS WONDERFUL SERIES OF VIDEOS but I only came across it by accident. It discusses, in great detail, the Cambrian Explosion.

My favourite (so far) is THIS ONE by Paul Smith, which among much else, describes looking for fossils in the very north of Greenland. But every thing I have seen so far is excellent and very professional - in the best sense!

Cambrian Ocean Scene

Thursday, 1 April 2021

Stonechat - April 2021

Stonechat - April 2021 

Another edition of this excellent club Magazine has appeared. You can get it HERE.

And you can read it below. There is a good article about Svalbard which contains (with much else) this:-