Lightless Life 

A correspondent brought THIS ARTICLE to my attention. It is based on THIS ACADEMIC PAPER.

Deep underground, abundant microbes produce oxygen in the absence of light - something which was once thought to be impossible. 

This discovery was made while looking at deep aquifers in Alberta, Canada. These have long been studied as they are essential to agriculture in the province. Much was known of their composition, nothing of their microbiology.

And what was found was that some bacteria split nitrites to produce oxygen.

It is estimated that there is more microbes below ground than on the surface!

Lots more in both articles - well worth a read.

 Icelandic Eruption - Continued

A correspondent told me about THIS YOU TUBE CHANNEL - it has some very good content about the current eruption.

Below is a sample.

 Down to Earth Extra August 2023

The August 2023 edition of Down to Earth Extra has been published. You can download it HERE or you can read it below.

A Geologic Quiz from the BBC 

A correspondent brought THIS QUIZ to my attention. And now I bring it to yours. 

I managed to do quite well - I got the Aberdeen one OK!

Earth Heritage 59 

You can download Earth Heritage 59 HERE, or read it below.

Two 1-Day Field Course with Nick Chidlaw

Two 1-Day Field Courses with Nick Chidlaw 

Nick Chidlaw has asked me publicise two field courses he will be running in September. These are independent of one another: enrollees can choose to do both or either, according to their availability / interests. Together, the courses examine exposures in most of the stratigraphic Formations of the Old Red Sandstone Supergroup in the area.

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 OLD RED SANDSTONE LOCATIONS IN THE SOUTHERN WELSH BORDERLAND: tropical arid-climate river deposits exposed by ice age and post-ice age processes; north east Black Mountains 

Saturday 9th September 10.00 am - 5.00 pm

The Old Red Sandstone Supergroup is found in many parts of the British Isles, and mostly represents the deposition of sediment eroded off mountains and uplands elevated during the Caledonian and Acadian Orogenies, in the Silurian and Devonian periods respectively. The British crust at these times was located in the southern tropics and had a hot arid-semi-arid climate with rainy and dry seasons. The sediment was transported by river systems and deposited across lowlands in channels, flood plains and lakes. 

The strata to be examined on this course includes the Freshwater West Formation and the Senni Formation, of Early Devonian age. They are exposed in small natural crags and big landslide scars on the NE margin of the Black Mountains, in Herefordshire. They represent a change over time from slower sinuous meandering rivers with extensive muddy floodplains to faster-flowing rivers with straighter courses and fewer muddy deposits. This progression of increasing energy continues with the younger Brownstones Formation, which can be seen in the higher parts of the Black Mountains further west or, more conveniently, at Ross-on-Wye (see 10th September course details below). The muddy sediments in the Freshwater West and Senni Formations contain developments of limestone nodules recognised as fossil soils. Fragmentary remains of fish and plants may be found in some of the the channel deposits. 

No previous knowledge of geology or the area will be assumed.   

 

Tuition fee: £30.00 

Contact tutor Dr Nick Chidlaw nickchidlaw@gmail.com to enrol and for any queries. 

Deadline for course viability: Saturday 12th August . If the course has become viable (minimum of 10 enrolments) by this date, enrolments will be able to continue until 1 week before the course runs (Saturday 2nd September ).   

Google Earth image of the study area in the north-east Black Mountains. The narrow ridge on the right of the image is known as the 'Cat's Back'  and provides accessible footpath exposures in the uppermost part of the Freshwater West Formation and the lower part of the Senni Formation. These strata are also exposed in the big landslide scars on the left of the image at 'Red Daren' and 'Black Darren'. 

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OLD RED SANDSTONE LOCATIONS IN THE SOUTHERN WELSH BORDERLAND: tropical arid-climate river deposits exposed by ice age and post-ice age processes; Ross-on-Wye and near Symonds Yat 

Sunday 10th September 10.00 am - 5.00 pm

The Old Red Sandstone Supergroup is found in many parts of the British Isles, and mostly represents the deposition of sediment eroded off mountains and uplands elevated during the Caledonian and Acadian Orogenies, in the Silurian and Devonian periods respectively. The British crust at these times was located in the southern tropics and had a hot arid-semi-arid climate with rainy and dry seasons. The sediment was transported by river systems and deposited across lowlands in channels, flood plains and lakes. 

The strata to be examined on this course includes the Brownstones Formation (Early Devonian age), and the Huntsham Hill Conglomerate Formation and Tintern Sandstone Formation (Late Devonian - earliest Carboniferous age). The Brownstones are exposed in a large road cutting and natural crags near the River Wye at the town of Ross, and the younger strata in extensive natural crags on the edge of the Forest of Dean near Symonds Yat. The Brownstones represent higher energy river systems than of those strata studied on the Black Mountains course. The late Devonian - earliest Carboniferous strata were deposited after the Acadian Orogeny (Mid Devonian times) and record a progression of decreasing energy river systems as uplands created during the Orogeny were progressively eroded down. 

No previous knowledge of geology or the area will be assumed.   

 

Tuition fee: £30.00 

Contact tutor Dr Nick Chidlaw nickchidlaw@gmail.com to enrol and for any queries. 

Deadline for course viability: Saturday 12th August . If the course has become viable (minimum of 10 enrolments) by this date, enrolments will be able to continue until 1 week before the course runs (Sunday 3rd September).   

Extensive exposure of the Brownstones Formation: road cutting at Wilton Bluff, Ross-on-Wye. This exposure (c. 5m high) is to be examined from a distance, then close-up examination of the strata will be done in accessible natural crag exposures to the SW. 

Exposure of the Huntsham Hill Conglomerate Formation next to a public footpath on the NW side of Huntsham Hill, near Symonds Yat. The crag is 6-7m high and was formed by periglacial frost action during the last glaciation. 

Exposures of the Tintern Sandstone Formation. Extensive periglacial crags on the E side of narrow, steep ridge forming the S side of Huntsham Hill. The nearest exposure is c. 4-5m high. 

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Britain Gets Earthquakes, Ireland Doesn't - Why? 

Intriguing fact in the heading above. The illustration below shows the evidence - on the left - and the reason - on the right. This come from THIS ARTICLE and gives rise to an important observation - Moderate variations in plate thickness, occurring far from plate boundaries, can influence patterns of seismic activity within those regions.

The fact that the island of Great Britain has more earthquakes than the island of Ireland has long been known. The cause has only recently come to our understanding. And it is seismic tomography which has given us the answers. The part of the tectonic plate below Ireland (and the eastern side of Great Britain) is thicker (95 - 115km) than that below western Britain (75 - 85km). 

The parent article is HERE but you need to pay for access. I suspect that the simple numbers for thickness I give above are the result of a great deal of work. This only adds to their interest.

 Down to Earth Extra July 2023

The July 2023 edition of Down to Earth Extra has been published. You can download it HERE or you can read it below.

 When was the First (Placental) Mammal?

There are three sorts of mammals: monotremes (platypuses), marsupials (kangaroos) and placentals (us and lots more).

How do you find the first placental mammal? I suppose you could find its fossil, be able to determine it is placental, date it, and (the difficult bit) prove that there are none which came before. This is unlikely and your conclusions are likely to be challenged. 

However there are a few fossils which are accepted as being placental mammals dated as living after the extinction of the dinosaurs. But were they the first? Were there placentals living alongside the dinosaurs? There are no accepted placental fossils in rocks below the K-Pg boundary, but that does not prove much.

There is another way, using molecular clocks. Much has been written about the use of molecular clocks - the more you get into it the more difficulties appear. See the diagram below to get a flavour of the controversies.

Thick purple lines are crown orders, green lines are stem orders, and black lines are stem placental families.

(A) Explosive model: all placental mammal diversification and origination occurred just after the K-Pg boundary.

(B) Soft explosive model: placental mammals originated just before the K-Pg boundary, but intraordinal diversification only occurred after the boundary.

(C) Trans-KPg model: both interordinal and intraordinal diversification occurred around the K-Pg boundary.

(D) Long fuse model: placental mammals originated in the middle of Late Cretaceous, but intraordinal diversification did not begin until after the K-Pg boundary.

(E) Short fuse model: placental origination and crown order diversification occurred during the Cretaceous.

The author of THIS ARTICLE, working at Bristol University, has avoided much of these controversies by comparing families and using statistical methods, of which I know little, to conclude that placental mammals originated in the Cretaceous

The article is based on THIS ACADEMIC PAPER. An indication of the depth of study used in the article can be gauged from the following figure.

Clade age and extinction time estimates for placental mammal families

Each line represents a family (arranged by order and clade but without further phylogenetic information), with 95% credible intervals in colors at the root estimates and extinction estimates (where applicable). Gray lines fill in the lineage. 93 families have credible intervals extending into the Cretaceous, but many originated after the K-Pg boundary. For stem and crown order classifications for each family, see Data S1.