The new species and Genus Spinaxinus sentosus, collected from the organic cargo of the sunken ship Francois Vieljeux. The genus bears little resemblance to other known thyasirids and remains the only record of this species.

Thyasira methanophila

, a clam new to science from a methane seepage area off Concepción, Chile. Its name suggests its dependence on methane.

An extreme magnification of the exterior shell covering of Spinaxinus sentosus, recovered from the organic cargo of the sunken ship Francois Vieljeux. The spines witnessed at this magnification lead scientists at the Museum to name the new genus 'Spinaxinus'.

Deep beneath the sea floor there are large reservoirs of oil and natural gas, but it is only relatively recently that methane has been discovered to seep from the surface of the sea bed. These areas are known as 'gas seeps' and certain animals have evolved specifically to take advantage of this unique environment.

A diet of methane and sulphur

Found alongside these methane gas seeps are communities of clams that use the gas as a source of food. They don't actually eat the gas but they have evolved to harbour bacteria in their tissues that do the job for them.

These organisms are known as 'chemosymbiotic' and a few groups of clams have been very successful in adapting to this environment.

The same group of clams can also exploit sulphur and these are found living in areas where there are layers of rotting vegetation, around decaying whale carcasses, at hot vents and even on mud contaminated with diesel oil.

Because these clams come from unusual environments and often from deep water, many have yet to be studied in detail. A number of these gas guzzling clams were sent to Amgueddfa Cymru - National Museum Wales for identification and description. Several scientific papers have now been written on these species new to science

Clams from Chile

Clam shells and whole specimens were sent to the Museum following the discovery of a methane seep off the coast of Chile at a depth of 700-900m. One of these species, belonging go the genus Thyasira, was new to science and has been described in a scientific paper. The bacteria in the gill tissue of the clam were studied using a scanning electron microscope. This confirmed the symbiosis (reliance) between the bacteria and the clam.

A species of the genus Lucinoma was also discovered to be new to science but only shells have been found so far. It is likely that the majority of species living at this site are endemic (restricted to this location) and found nowhere else in the world.

The Pakistan Margin

From the other side of the world, we were sent a small species from the same group as the Chilean bivalve - Thyasira - but from the Indus Fan, off the coast of Pakistan, collected while investigating the unusual fauna that live in the very low oxygen waters of this region. The Museum worked with the Natural History Museum, London to investigate the DNA alongside describing the anatomy and shell of this bivalve.

A clam with a taste for shipwrecks

Man-made sources of methane and sulphur are also exploited and one of the strangest was the cargo of the sunken container ship Francois Vieljeux. This ship sank off the north coast of Spain in 1,160m of waters, taking with it its cargo of castor beans and sunflower seeds.

During attempts to salvage the vessel it was noted that clams had settled and grown on the cargo. All the clams belonged to chemosymbiotic groups and were exploiting the sulphur released by the rotting cargo. One clam was a Thyasira, similar to the specimen from Chile.

Cascadia Basin, off Washington State

The Baby Bare Seamount in the north-east Pacific Ocean is a hot spring and home to a new species of Axinus (similar to Thyasira). This site is unusual in that no other species of bivalve typically found at other methane seeps and hot vent sites are found here. Methane and Hydrogen sulphide levels are low, so initially it was a mystery as to what these animals were using as nutrition.

Cadiz Mud Volcanos

Off the Southern coast of Portugal there are numerous marine mud volcanoes created by stresses on the African and Eurasian tectonic plates. These stresses cause hot, methane and sulphur rich fluids to eject from deep within the volcanoes out into the sea bed above. By the time the fluids reach the sediment surface they are cold, so the mud volcanoes are classed as cold-seeps. Many species of Thyasira clams are found at some of these sites, but only a few are known to harbour the chemosymbiotic bacteria that help them to extract nutrition from sulphur and methane. A collaboration between the Museum and Cadiz University, Spain has resulted in the newly described species Thyasira vulcolutre , meaning 'belonging to mud volcano'.

Finally, in conjunction with Bangor University, the Museum is carrying out the taxonomic work on a Thyasira collected from a mud volcano in the Arctic and a mussel of the genus Idas which was collected from diesel contaminated mud beneath an oil rig in the North Sea.

This work by Amgueddfa Cymru - National Museum Wales is helping research the possibility of using these clams to clean up contaminated areas of the sea bed.

Although not competing with areas famous for their instability such as western California, Japan or Sumatra, Wales is a region of regular active Earth movements. You might be surprised to learn that at least sixteen significant earthquakes have occurred in Wales during the last century.

Seismograph showing an earthquake in north Wales in 1994

Why do earthquakes occur in Wales?

The British Geological Survey (BGS) records around 300-400 earthquakes each year in Britain. Wales, along with the rest of the UK, sits on the European plate, and stress builds up as it is pushed slowly north-eastwards from the Mid-Atlantic Ridge. The stress is released by movement along pre-existing fault planes, causing an earthquake.

Where do earthquakes occur in Wales?

There are several long-active fault systems in Wales. Once faults form, they create weak zones in the crust that can be reactivated time and time again. For example, the fault system running parallel to the Menai Strait between Anglesey and Bangor in north Wales are known to have been active over 500 million years ago and have also been the sites of more recent earthquakes.

The Menai Strait area is the most seismically active area in Wales and one of the most active in the UK. The last major earthquake occurred here in 1984, but many others are known from historical records (including 1827, 1842, 1852, 1874, 1879, 1903). Although many events have been recorded in south Wales, from Pembroke to Newport, only the Swansea area shows consistent activity, with significant earthquakes occurring in 1727, 1775, 1832, 1868 and 1906.

Largest earthquake in Wales for 100 years

The 1984, magnitude 5.4, Menai Strait earthquake was the largest onshore UK event for over 100 years. The epicentre was located in northern Llŷn, north Wales and the quake originated at a depth of approximately 22 km in the Earth's crust.

Another major UK earthquake occurred on 2 April 1990 in the Welsh Borders. This magnitude 5.1 event was felt over an area of approximately 140,000 square kilometres and was followed by six aftershocks. The epicentre was initially identified as being at Bishop's Castle in Shropshire, but this was later revised to a location just inside the Welsh border (latitude 52.43°' N, longitude 3.03° W).

Local damage

In both earthquakes the damage was relatively minor, including cracks in plaster and masonry and collapse of chimneys. In the Bishop's Castle event this was limited to the area immediately around the epicentre.

The only fatality known from any seismic activity in Wales is from a woman falling down the stairs and being killed during the Porthmadog earthquake of 1940.

Recent activity

An earthquake with a magnitude of 4.6 occurred in south Wales on February 17, 2018. According to the British Geological Survey (BGS), its epicentre was between Ystradgynlais and Ystalafera. A Welsh earthquake also occurred in the Bristol Channel on 20th February 2014, and was widely felt across South Wales, Devon, Somerset and western Gloucestershire. The BGS received several reports from the media and local residents describing “felt like the vibration of a large vehicle passing the building”, “the whole house seemed to move/wobble back and forth a few times”..

The magnitude 4.1 earthquake is the largest to hit South Wales since 2013.

Other recent earthquake activity from Wales include:

• A magnitude 3.8 earthquake on the Lleyn Peninsula on 29th May 2013.
• Magnitude 2.9 earthquake near Nantyffyllon on 5th June 2009.
• Magnitude 2.9 earthquake near Llangollen on 30th November 2007
• A magnitude 2.9 quake in Cardiff on 20th June 2002.

In general, humans cannot feel events of less than magnitude 2.

Recording earthqake activity at Amgueddfa Cymru.

A seismograph at National Museum Cardiff displays output from a local seismometer and allows observation of data from seismic events.

As seismometers are very sensitive to all types of ground vibrations, not only earthquakes but local traffic, trains and even roadworks, it was not possible to locate a seismometer in Cardiff city centre. Instead, data is obtained by a radio link from the nearest BGS seismometer near Newport, Gwent.