Sciency Thoughts: Somerset

Showing posts with label Somerset. Show all posts

Saturday, 3 February 2024

Record number of breeding Eurasian Cranes in the UK in 2023.

In 2023 a record number of Eurasian Cranes, Grus grus, were observed breeding in the UK, with eighty observed pairs, the highest number seen since the species was re-introduced in the 1970s. Eurasian Cranes were once abundant in the UK, but a combination of heavy hunting and the drainage of wetlands to create new agricultural land led to the species becoming locally extinct in the sixteenth century.

A pair of Eurasian Crans, Grus grus, during a courtship dance. RSPB.

While Cranes dissapeared as a resident species, occasional individuals were observed in the East of England in spring and autumn, during their annual migration between their summer breeding grounds in Europe (almost certainly Scandinavia for these Birds) and their wintering grounds in Africa. Then, in 1979, a single pair was observed to remain in the UK, breeding on Hickling Broad in Norfolk. From this point on a growing number of breeding pairs of Cranes were observed on the Norfolk Broads, with the Birds slowly expanding their range to reach Suffolk, Cambridgeshire, and South Yorkshire in England, as well as parts of Aberdeenshire in Scotland.

In addition to this, a reintroduction program was set up on the Somerset Levels in the West of England in the 2010s, with eggs collected from Brandenberg in Austria being incubated and raised in captivity between 2010 and 2014, before being released onto the Levels. Cranes were first observed breeding in Somerset in 2015, although breeding remained slow their for some years, possibly because the Birds were hand-reared, which can hamper the ability of Birds to acquire courting and chick-rearing skills, but from 2021 onwards the Somerset population began to breed at similar rates to Cranes elsewhere in the UK. In 2022, twenty six pairs of cranes were observed breeding on the Somerset levels, out of a total UK population of 69 breeding pairs of the Birds.

A young Eurasian Crane, Grus grus, in flight on Sutton Fen in Somerset, England. RSPB.

Sunday, 22 October 2023

A new Odonatan Insect from the Latest Triassic or Earliest Jurassic of Somerset, England.

Odonatopteran Insects, the group which includes the modern Damselflies and Dragonflies first appeared in the Carboniferous, with a variety of groups including the spectacular Griffenflies, Meganeuridae, which had wingspans of up to 71 cm, making them the largest flying Insects ever known to have lived. The crown group Odonata (a crown group includes all living members of a clade, the most recent common ancestor of all those members, and everything descended from that ancestor) first appeared in the Triassic, including the living Damselflies, Zygoptera, and Dragonflies, Anisoptera, as well as a number of extinct groups. One of these is the Liassophlebiidae, was first described in 1925 by palaeoentomologist Robin John Tillyard based upon specimens from the Late Triassic and Early Jurassic of Warwickshire and Worcestershire, England, which he assigned to the genus Liassophlebia. The Family Liassophlebiidae now includes five genera from the Triassic and Jurassic of Western Europe, Central Asia, and Antarctica, while the genus Liassophlebia includes five species from the Triassic of England and Jurssic of England and Germany.

In a paper published in the journal Historical Biology on 16 October 2023, Emily Swaby and Angela Coe of the School of Environment, Earth and Ecosystem Sciences, at the Open University, Deborah Hutchinson of the Bristol Museum & Art Gallery, Lee Riva of the Lovell Stone Group, and André Nel of the Institut de Systématique, Évolution, Biodiversité at the Muséum national d’Histoire naturelle, describe a new specimen of Liassophlebia from the White Lias Formation of Bowdens Quarry in Somerset, England.

The specimen was discovered at Bowdens Quarry in 2016 by Lee Riva, the quarry foreman, and subsequently donated to the Bristol Museum & Art Gallery. It comprises a split piece of fine-grained crystalline limestone with a partial forewing preserved as part and counterpart. Due to the fragmentary nature of this specimen it is ascribed to the genus Liassophlebia, but not to a specific species.

Liassophlebia sp., specimen BRSMG Cg3101 a+b: (A) BRSMG Cg3101 a, part; (B) BRSMG Cg3101 b, counterpart; (C) line drawing of BRSMG Cg3101 b, highlighting wing venation. Abbreviations: A×1, second branch of primary antenodal crossvein; CuA, anterior cubitus; DC, discoidal cell; MA, anterior median; MP , posterior median; N, nodus; Pt, pterostigma; RP3/4, third/fourth branch of posterior radius. Scale bars are 5 mm. Swaby et al. (2023).

The precise stratigraphic age of the deposits at Bowdens Quarry (and of the White Lias in general) is unclear. Bowdens Quarry comprises the uppermost part of the White Lias and the lowermost part of the overlying Blue Lias. Biostratigraphic data from the White Lias at Lavernock in Wales suggests that at least the uppermost part of the formation is Early Jurassic in age, whereas isotopic data from St Audrie’s Bay in Somerset suggests that the base of the White Lias coincides with the End Triassic Extinction Event (which actually comes slightly before the Triassic-Jurassic boundary, which is marked by the appearance of distinctly Jurassic forms during the post-extinction recovery).

(A) A geographic map highlighting the extent of Penarth Group in England and Wales (outcrop shown in purple), and location of Bowdens Quarry (red circle). Note that the outcrop has been simplified for clarity. B) Close-up of the study area (Langport, Somerset), indicating the location of Bowdens Quarry. (C) Simplified stratigraphic log of the Late Triassic-Early Jurassic succession from the Langport-Somerton area, showing the interval that BRSMG Cg3101 a+b came from. Based on lithology, the ‘lower’ White Lias is interpreted to be equivalent to the White Lias Formation on the Somerset coast and the ‘upper’ White Lias to the Watchet Mudstone Formation. MMG denotes the Mercia Mudstone Group and WL the White Lias. Swaby et al. (2023).

Robin John Tillyard described two species of Liassophlebia, Liassophlebia magnifica, from the Earliest Jurassic of Binton in Warwickshire, and Liassophlebia withersi, Latest Triassic of Strensham in Worcestershire. Unfortunately, Liassophlebia withersi was also described from extremely fragmentary material, so that, while it appears to come from a larger Insect that the new specimen, it cannot be confidently stated that the two are different species, with the effect that the new specimen does not help resolve the date of the White Lias at Bowdens Quarry.

An artist’s impression of Liassophlebia sp., resting on a frond of the Palaeofern species Phlebopteris muensteri. the forewings are based on the specimen BRSMG Cg3101 a+b. As the new specimen is incomplete, other specimens within the genera were used to create this artist’s impression as follows: the hindwing is based on the holotype specimen of Liassophlebia magnifica (NHMUK I.6648/I.10462); and the body proportions are based on the incomplete abdomens of the holotypes ‘Liassophlebia’ clavigaster (NHMUK I.10433) and ‘Liassophlebia’ hopei (OUMNH J.55084 a and b). The colour and body morphology, including resting wing posture is inferred from present day Anisoptera. Jules Kiely/Bristol Museum & Art Gallery in Swaby et al. (2023).

Tuesday, 12 May 2020

Magnitude 1.4 Earthquake near Bridgewater in Somerset, England.

The British Geological Survey recorded a Magnitude 1.4 Earthquake at a depth of about 7 km, roughly 5 km to the northwest of the town of Bridgewater in Somerset, England, slightly after 8.15 pm British Summertime (slightly after 7.15 pm GMT) on Saturday 9 May 2020. There are no reports of any damage or injuries associated with this event, and nor would they be expected from such a small event, though it may have been felt locally.

The approximate location of the 9 May 2020 Somerset Earthquake. Google Maps.

Earthquakes become more common as you travel north and west in Great Britain, with the west coast of Scotland being the most quake-prone part of the island and the northwest of Wales being more prone to quakes than the rest of Wales or most of England. However, while quakes in southern England are less frequent, they are often larger than events in the north, as tectonic pressures tend to build up for longer periods of time between events, so that when they occur more pressure is released.

The precise cause of Earthquakes in the UK can be hard to determine; the country is not close to any obvious single cause of such activity such as a plate margin, but is subject to tectonic pressures from several different sources, with most quakes probably being the result of the interplay between these forces.

Britain is being pushed to the east by the expansion of the Atlantic Ocean and to the north by the impact of Africa into Europe from the south. It is also affected by lesser areas of tectonic spreading beneath the North Sea, Rhine Valley and Bay of Biscay. Finally the country is subject to glacial rebound; until about 10 000 years ago much of the north of the country was covered by a thick layer of glacial ice (this is believed to have been thickest on the west coast of Scotland), pushing the rocks of the British lithosphere down into the underlying mantle. This ice is now gone, and the rocks are springing (slowly) back into their original position, causing the occasional Earthquake in the process.

Witness accounts of Earthquakes can help geologists to understand these events, and the structures that cause them. If you felt this quake, or were in the area but did not (which is also useful information) then you can report it to the British Geological Survey here.