Sunday 31 May 2015

Natural gas pipeline blown up in North Sinai Province, Egypt.

An explosive device was used to blow up a natural gas pipeline on the outskirts of el-Arish, the provincial capital and principle port of North Sinai Province in Egypt early in the morning of Sunday 31 May 2015. Nobody was hurt in the incident, and firefighters were able to extinguish the blaze quickly after the gas supply was cut off. The pipeline supplies homes and a power station in el-Arish.

The approximate location of the 31 May 2015 el-Arish pipeline explosion. Google Maps.

No one has claimed responsibility for the bombing, however it is thought likely to have been the work of Ansar Beit al-Maqdis, a militant group based in the Sinai Peninsula which has pledged allegiance to the Islamic State group in Syria and Iraq. Ansar Beit al-Maqdis has previously carried out bombings against Egyptian security services, as well as oil and gas facilities, a favored target for Islamic State-affiliated groups.

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The flow of oil from the El Sarir Oilfield to the Mediterranean port of Hariga was halted by a bomb which blew up part of a pipeline several kilometers...

A fire is burning out of control at a fuel storage facility in Tripoli, after a tank holding 6 million liters of oil was hit by a rocket during fighting between militia groups...

A pipeline carrying Marib Light Crude from the  Safer Oilfield to the port of Ras Isa on the Red Sea reopened on Thursday 24 July 2014, forty two days after it was blown up by unknown insurgents near the town...

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Eruption on Wolf Volcano.

At about 11.50 pm local time on Sunday 24 May 2015 the Instituto Geofísico-Escuela Politécnica Nacional recorded a sudden rise in seismic activity (Earthquakes) beneath Wolf Volcano, which is located on the northern tip of Isabella Island in the Galapagos. This was followed at 2.15 am on Monday 25 May by a major eruption which according to the  Washington Volcanic Ash Advisory Center, produced an ash column 10.7 km high, that subsequently drifted 65 km to the southwest. A second major eruption at 3.45 am produced a 15.2 km high plume which drifted 250 km to the east, while a third eruption shortly after produced a 13.7 km high plume which drifted 250 km to the east. At 4.28 am NASA’s MODIS satellite, which monitors infra-red emissions, detected a significant thermal anomaly on the southeastern flank of the volcano, which would generally indicate a lava eruption, which was later confirmed by investigators from the Galápagos National Park, who reported a new fissure close to the southeastern rim of the caldera, which was producing several major lava streams.

The May 2015 eruption on Wolf Volcano. Diego Paredes/AFP.

These eruptions continued throughout Monday 25 and Tuesday 26 May, before eventually subsiding, producing significant lava flows and smaller ash columns, as well as several hundred kilotons of sulphur-dioxide emissions. There was initial concern that the eruption might present a threat to the volcano’s distinctive fauna; the volcano is a distinct environment compared to the rest of the island, and hosts a unique set of animals of its own, including the Wolf Giant Tortoise, Chelonoidis nigra becki, and Pink Land Iguana, Conolophus marthae, though these are concentrated on the northwest flanks of the volcano and are unlikely to have been harmed by an eruption on the southeastern flanks.

A Pink Land Iguana, Conolophus marthae. Alamy.

Wolf Volcano is the highest volcano in the Galapagos, reaching 1707 m above sea level, with an oval crater measuring 6 km by 7 km orientated in a northwest-southeast direction. Like all the volcanos of the Galapagos it is a shield volcano, i.e. a volcano made up largely of overlapping lava deposits that resembles an upturned bowl rather than a cone. The placement of this volcano on the northern tip of Isabella Island creates a unique microhabitat on the northwestern flanks of the volcano, cut off from the rest of the island by the steep, smooth lava flows of the main peak. This has served to protect the wildlife of the volcano from invasive species such as feral Cats and Goats, which threaten much of the unique fauna of the Galapagos (though Goats have recently been sighted here). As well as its own unique Tortoise, the Wolf Volcano ecosystem is also home to several populations of introduced tortoises from other islands, including at least two possible specimens of the Pinta Island Giant Tortoise, Chelonoidis nigra abingdoni, thought to have gone extinct with the death of Lonesome George in 2012, which are currently under investigation by wildlife geneticists from Yale University and the Galapagos Conservatory.

Lonesome George, the last known surviving specimen of the Pinta Island Giant Tortoise, Chelonoidis nigra abingdoni, prior to his death in June 2012. Wikipedia.

The volcanos of the Galapagos are fuelled by a mantle plume, the Galapagos Hotspot, an upwelling of hot magma from deep within the Earth’s mantle which pierces the overlying Nazca Plate, and moves independently of it. This plume transverses the plate at a rate of 0.46 degrees per million years, which has led to the formation of the string of volcanoes which form the Galapagos Islands. However analysis of the geochemical composition of the lavas of Wolf Volcano has shown that these are distinct from the lavas of the neighbouring Ecuador and Darwin volcanoes, but show strong similarities to lavas produced on the Galapagos Spreading Center over 200 km to the north, a trait shared with lavas from other Galapagos volcanoes, most notably Santa Cruz and Genovesa, suggesting that there is some interplay between these two sources.

The relative positions of the Galapagos Islands and Galapagos Spreading Center. School of Ocean and Earth Science and Technology/University of Hawaii at Manoa.

Wolf Volcano is the most active volcano in the Galapagos, it was first observed erupting in 1797 and most recently in 1982; the 2015 eruption is the eleventh recorded eruption on the volcano, which is believed to be slightly less than 500 000 years old, compared to an age of about 10 million years for the surrounding seafloor. It takes its name from Theodor Wolf, a German geologist who made the first organized study of the volcanoes of the Galapagos in the nineteenth century, and after whom Wolf Island is also named.

See also…

Authorities in Chile have began to evacuate homes within 20 km of Mount Calbuco, a volcano in the Los Lagos Region in the south of the country, after the volcano began to erupt at about 6.00 pm local...

Authorities in Chile have began to evacuate people from the vicinity of Volcán Villarrica, following a major eruption overnight between Sunday 1 and Monday 2 March 2015. Villarrica is active at some level more-or-less all of the time, but in mid February the level...

The Vanuatu Geohazards Observatory issued a warning to the public on Saturday 21 February following an eruption from a new vent inside the caldera of Mount Ambrym a volcanic island in the New Hebrides. The eruption is apparently small in nature, but its...

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Magnitude 4.7 Earthquake in the Gulf of Tadjoura, Djibouti.

The United States Geological Survey recorded a Magnitude 4.7 Earthquake at a depth of 9 km, beneath the Gulf of Tadjoura on the coast of Djibouti, slightly before 9.50 am local time (slightly before 6.50 am GMT) on Saturday 30 May 2015. There are no reports of any damage or injuries arising from this quake, but it was felt in much of northeastern Djibouti.

The approximate position of the 30 May 2015 Gulf of Tadjoura Earthquake. Google Maps.

Djibouti is located on the western shore of the Red Sea, which while referred to as a sea, is technically an immature ocean, underlain by the Red Sea Rift, a spreading boundary between two tectonic plates, the African Plate and the Arabian, where new oceanic crust is being formed. Arabia was formerly part of the African Plate, but split away about 30 million years ago. The Great Rift Valley of Africa is a continuation of this rift, that is slowly splitting Africa in two from the north to the south. This rifting exerts pressure on the rocks around the margin of the sea, slowly pushing them apart, not smoothly but in fits and starts as the pressure overcomes the tendency of the rocks to stick together.

See also...

The Zubair Archipelago are a group of volcanic islands off the southwest coast of Yemen; they are essentially a shield volcano on the Red Sea Rift with a number of...

The Afar Depression lies at at northernmost end of Africa's Great Rift Valley, where it meets the sea at the junction between the Red Sea and the Gulf of Aden. All three of these features are areas of rifting, with Africa slowly being split into two new continental plates...

The United States Geological Survey recorded a Magnitude 5.0 Earthquake at a depth of 9.8 km, on the Eritrean coast 19 km to the north of the port...

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Major pollution incident after oil pipeline ruptures in Santa Barbara County, California.

Clean-up crews are struggling to cope after a ruptured pipeline was discovered to have leaked around 2500 barrels (400 000 litres) of crude oil in Santa Barbara County, California, on Tuesday 19 May 2015. The pipeline, operated by Plains All American, was initially shut down after a mechanical problem was encountered at 10.45 am, then restarted at 10.55, before being shut down by a remote operator at 11.30 after a drop in pressure was detected. At 11.42 the Santa Barbara Fire Department received a call reporting a ‘pungent oil smell’ on Refugio Beach, leading to an investigation which at 12.20 pm led to firefighters discovering crude oil flowing from a culvert (storm drain) onto the beach.

Oil collected by volunteers from Refugio Beach on 21 May 2015. Jae Hong/AP.

The Santa Barbara Fire Department notified Plains All American, who sent a response team that constructed a sand and rock barrier to block further oil from escaping from the culvert, and estimated that around 21 000 gallons of oil (500 barrels or 80 000 litres) had been released, an estimate which was later raised to 105 000 gallons (2500 barrels or 400 000 litres), of which around 20 000 gallons (480 barrels or 75 000 litres) of oil is thought to have entered the sea. At this time the Coast Guard, National Response Center and Environmental Protection Agency were notified, and several local beaches were closed to the public and fishing and shellfish harvesting banned in the local area.

The source of the May 2015 Santa Barbara oil spill, and the culvert through which it reached the beach. John Wiley/Wikipedia.

Shortly after the spill was discovered volunteer teams began a clean-up operation, though they struggled to cope due to the scale of the spill, and report that they were not joined by professional clean-up teams employed by Plains All American, or the county, state or federal government for ‘several days’.  A week after the incident was reported it was estimated that less than 6% of the escaped oil had been recovered, and a large number of oiled Seabirds and Seals have reported, and where possible taken to recovery centres for treatment. Significant numbers of dead Fish and Invertebrates have also been reported, and concerns have been raised that the oil may present a threat to Whales, which migrate through the area at this time of year.

Volunteers clean an oiled Pelican at a center run by the UC-Davis led Oiled Wildlife Care Network. East County Magazine.

The Santa Barbara Channel was the scene of a major oil spill in 1969, in which 3.4-4.2 million gallons (81 000-100 000 barrels or 13 000 000-15 000 000 litres) of crude oil escaped from an oil well blowout which was not capped for 10 days. This incident led directly to the formation of a number of prominent US environmental protest groups, and a tightening of environmental restrictions in Santa Barbara County, where all pipelines are now supposed to be fitted with automatic cutouts (which detect drops in pressure within pipelines and shut off the supply of oil without human intervention). Since the introduction of these regulations only a single major incident has occurred, when in 1997 a platform operator manually overrode an automatic cutout on a pipeline connecting an oil well to the shore which had a faulty weld, leading to the spillage of 6800 gallons (160 barrels or 26 000 litres) of crude oil.

Volunteers cleaning oil from a Santa Barbara beach in 1969. The oil is being soaked up with straw, which is then placed in drums for removal. AP.

However it has been reported this week that Plains All American won exemption from regulation by Santa Barbara County in a court case in the 1990s and the affected pipeline was not fitted with an automatic cutout. This is of particular concern as the amount of oil lost from the pipeline, 2500 barrels, represents over an hour of pumping at the pipeline’s maximum capacity (2000 barrels per hour) and nearly two hours at the rate at which the pipeline was being operated (1300 barrels per hour), implying that even if 100% of the oil was being lost from the pipeline (unlikely) it still took two hours for Plains All American to detect the fault, and that if a lower percentage of oil was being lost the leak must have persisted for several hours.

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Four people were taken to hospital with minor injuries and four more were subjected to contamination procedures following an explosion at a gasoline...

A cleanup operation is under way after a pipeline carrying crude oil from Bakersfield to Texas burst in the...

It emerged this week that hydraulic fracturing (fracking) has been in regular use in the oil fields of the Santa Barbara Channel off the coast of California since the late 1990s. There has been a moratorium on new drill leases in the area since a spill in 1969 which...

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Saturday 30 May 2015

Analysing the distribution of shallow-water Black Corals in the Hawaiian Archipelago.

Black Corals, Antipatharia, are Anthozoan Hexacorallid Corals known from across the world’s oceans, particularly in waters below the photic zone, waters shallower than about 50 m where light levels are high and attached benthic communities are dominated by photosynthetic organisms, such as Macroalgae (Seaweeds) and Coral species which host symbiotic single-celled Algae, and have been recorded at depths below 8600 m in the Western Pacific. All Black Corals are colonial, they have largely proteinaceous skeletons with minute spines, mouths surrounded by eight non-retractable tentacles and stomachs with eight mesentery canals (single-ended digestive canals which much be emptied of waste matter by periodic eversion). Because most Black Corals live at depths where surveys by Scuba divers are impossible, very little is known about their distributions, with most species known only from single records, though in some areas where shallow-water Black Corals occur better records exist.

One area where such shallow-water Black Corals are abundant is the Hawaiian Archipelago. Here Black Corals are of some economic significance, having been used in traditional Hawaiian medicine, and with a commercial harvesting industry which collects Black Corals for the jewellery industry (Black Coral is the official State Gemstone of Hawaii). As such a large number of surveys of Black Corals at shallow depths have been carried out in Hawaii, although these are generally local in nature and concentrated around the inhabited islands in the southeast of the archipelago.

In a paper published in the journal Marine Biodiversity Records on 17 April 2015, Daniel Wagner of the NOAA’s Papahānaumokuākea Marine National Monument publishes an analysis of the distribution of shallow-water Black Coral species from the Hawaiian Archipelago, based upon collected surveys from the harvesting industry, collection records from museum specimens, and photographic and video records from submersible surveys carried out by the Hawai‘i Undersea Research Laboratory and Monterrey Bay Aquarium Research Institute as well as published records in scientific literature.

For the purpose of this study ‘shallow-water’ was defined as less than 150 m from the surface, the base of the mesophotic zone (the zone below the photic zone where photosynthesis is not carried out but the water is not in permanent darkness) in the clear waters of Hawaii. A total of eight species of Black Corals were recorded, though since the surveying was somewhat patchy in the northern part of the islands this cannot be concluded to be an exhaustive list of the species present. All species grow attached to hard substrates and favour areas of high currents; it is likely that the current affects the distribution of these Corals, but sufficient records were not available to include this in the survey.

The first species recorded is Antipathes griggi, a commercially significant species found throughout the islands from Hawai‘i to Pearl and Hermes Atoll at depths of between nine and 110 m, but most abundant between forty and fifty meters and fairly rare below sixty meters. The species was found to tolerate temperatures of 22.30-27.41˚C, and has a dense bushy crown which extends into the current flow.

(Left) Growing specimen of Antipathes griggi. (Right) The known distribution of the species within the Hawaiian Archipelago. Wagner (2015).

The second species recorded is Antipathes grandis, another commercially important species which is found from from Hawai‘i to Ni‘ihau at depths of depths of between 24 and 146 m, but which is most abundant between 90 and 110 m, and fairly uncommon shallower than 50 m or deeper than 120 m. This species also has a dense bushy crown, and lives at temperatures of 20.01-26.91˚C.

(Left) Growing specimen of Antipathes grandis. (Right) The known distribution of the species within the Hawaiian Archipelago. Wagner (2015).

The third species recorded is Cirrhipathes cf. anguina (i.e. probably Cirrhipathes anguina a specimen cannot actually be confirmed as belonging to a species without comparing it to the holotype – first specimen described – which with some older species, such as Cirrhipathes anguina which was described in 1846, is not always possible) which is found from across the archipelago from Hawai‘i to the north-west of Brooks Banks at depths of between nine and 150 m, although it is less common below 60 m. Cirrhipathes cf. anguina is a wire Coral (i.e. its colonies consist of a single wire-like strand) found at temperatures of 21.92-27.69˚C.

(Left) Growing colonies of Antipathes grandis. (Right) The known distribution of the species within the Hawaiian Archipelago. Wagner (2015).

The fourth species recorded is Stichopathes echinulata, which is found across the archipelago from Hawai‘i to Lisianski, at recorded depths of 90-150 m, and probably also deeper than it was possible to evaluate using the records available for this study. Stichopathes echinulata forms unbranching wire-shaped colonies and lives at temperatures of 19.59-22.91˚C.

(Left) Growing colony of Stichopathes echinulata being manipulated by the arm of a submersible. (Right) The known distribution of the species within the Hawaiian Archipelago. Wagner (2015).

The fifth Coral species recorded is Stichopathes? sp. (an unidentified species of Coral which probably belongs to the genus Stichopathes) which was found from Hawai‘i to French Frigate Shoals at depths of 9-58 m, though it was never abundant. This species also forms unbranching wire colonies, though insufficient data was available to determine its temperature preferences.

(Left) Growing colonies of Stichopathes? sp. (Right) The known distribution of the species within the Hawaiian Archipelago. Wagner (2015).

The sixth Coral species recorded is Aphanipathes verticillata, which has been found only in the Keyhole Pinnacle area of the Au‘au Channel, at depths of 88-130 m. This species forms flat branching colonies and is found at a temperature range of 19.88-22.96˚C. The Hawaiian population of Aphanipathes verticillata was only discovered in 2008, and is thought to be a distinct subspecies, Aphanipathes verticillata mauiensis, though it closely resembles the related Antipathes griggi, and cannot be differentiated without close examination of the polyps, making it likely that many older surveys have failed to identify this species, and that it is more widely distributed within the Hawaiian Archipelago than is currently appreciated. Other populations of Aphanipathes verticillata are known from Mauritius and Okinawa, which supports the idea of this species being more widely distributed.

(Left) Growing colonies of Aphanipathes verticillata mauiensis. (Right) The known distribution of the species within the Hawaiian Archipelago. Wagner (2015).

The seventh species of Coral recorded is Acanthopathes undulata, which is found across the archipelago from Hawai‘i to Laysan at depths of 32-150 m, although it is more common below 100 m. Acanthopathes undulata forms branching colonies. It was not possible to establish a range of temperature preferences for this study.

(Left) Growing colonies of Acanthopathes undulata. (Right) The known distribution of the species within the Hawaiian Archipelago. Wagner (2015).

The final species recorded was Myriopathes cf. ulex, which is a commercially exploited species found across the archipelago from 30-150 m; it is more commonly recorded at depths of 60 m or shallower, though this may reflect the limit of harvesting potential rather than the true distribution of colonies, and the species may also be present deeper than 150 m, the limit of the survey. Myriopathes cf. ulex forms densely branching fan-shaped colonies, and has a temperature range of 20.52-26.99˚C.

(Left) Growing colonies of Myriopathes cf. ulex. (Right) The known distribution of the species within the Hawaiian Archipelago. Wagner (2015).

All of the Coral species examined in this study had depth and temperature ranges which overlapped with other species. Nevertheless there was clear separation in the habitat preferences of these species, particularly in mean temperature (the average temperature at which colonies were found), with Antipathes griggi colonies found in waters with an average temperature of 26.25˚C, Cirrhipathes cf. anguina having a mean temperature of 26.27˚C, Antipathes grandis 24.25˚C, Myriopathes cf. ulex 22.56˚C, Aphanipathes verticillata 21.19˚C and Stichopathes echinulata 21.08 ˚C. Furthermore, where species pairs had close mean temperature preferences, such as Antipathes griggi and Cirrhipathes cf. anguina or Aphanipathes verticillata and Stichopathes echinulata, they quite often had very different polyp sizes, suggesting that they were exploiting different resources. It is very likely that the distribution of these Corals is affected by other factors, such as current speeds and food supply (i.e. the amount of edible food in the water passing over them), but these were beyond the scope of the current study.

See also…

A new species of Soft Coral from the Republic of Congo.

Soft Corals (Octocorals) of the genus Alcyonium form encrusting, lobed colonies on shallow rocky surfaces in tropical waters. These Corals typically have...

The Abrolhos Bank is an area of the Brazilian continental shelf to the south of Bahia State, noted for its large and rich coral reef fauna and unique geochemical nature, with high levels of siliclastic material...

Zoanthids are unusual Corals with similarities to both the reef-forming calcareous skeleton excreting Scleractinian Corals and the larger, free living Sea Anemones. Most species are colonial, with individual polyps connected by tissue as in the Scleractinians...

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Death toll from Indian heat wave exceeds 2000.

The death toll from the heat wave that has hit India in May 2015 passed the 2000 mark on Friday 29 May 2015, with the majority of the casualties recorded in Andhra Pradesh and Telangana States, and loss of life attributed directly to the heat also recorded in Odisha, West Bengal, Gujarat, Delhi, Madhya Pradesh, Maharashtra, Rajasthan, Chhattisgarh, Punjab, Uttar Pradesh and Bihar. Temperatures began to soar on Thursday 21 May, when a temperature of 45.4°C was recorded in Jharsuguda in Odisha State and the first twelve deaths associated with the heat wave were recorded. On the same day a temperature of 42.6°C was recorded in Delhi, where several instances of roads asphalt roads melting were also observed and a temperature of 46°C was recorded in Hyderbad.

Woman carrying water in southern India. AAP.

On Saturday 23 May a temperature of 47°C was recorded in Allahabad in Uttar Pradesh, while 44.5°C was recorded in Delhi, 36°C in Kolkata and 43.6°C in Hyderbad, and a total of 246 heat-related deaths were recorded in Andhra Pradesh and 23 in Odisha. On 24 May a temperature of 48°C was recorded at Khammam in Telangana State.

People sleeping on the roofs of houses in New Delhi on 29 May to escape heat trapped within the buildings. Tsering Topgyal/AP.

High temperatures are normal in India, and Indian Summer heat waves that claim many lives have been recorded on previous years. Prior to 2015 the highest number of casualties were recorded in 1997, when 1677 heat-related deaths were recorded, and the number of such deaths passed 1200 in 2012 and 2013. However the 2015 heat wave is exceptional not just in the number of deaths recorded but in how early in the year it has struck; the Indian Summer typically lasts from March to July, with temperatures climbing steadily across this period, and relief arriving with the onset of the Monsoon Season. The record-breaking temperatures and high number of casualties recorded in May is alarming as the temperature could potentially continue to rise for another two months, leading to many further casualties and severely stretching the Indian infrastructure, which is already suffering water shortages in many places, as well as power outages caused by a sharp rise in demand for air conditioning.

Distorted road makings caused by melting of an asphalt road in New Delhi. Harish Tyagi/EPA.

Heat stroke typically occurs when the human body is heated to over 40°C; such temperatures the body rapidly becomes too dehydrated to allow further sweating and the body looses its ability to thermoregulate, leading to disorientation and occasionally seizures, followed by  unconsciousness and eventual death. The best way to avoid this is to remain indoors during the hottest parts of the day, and to cover up with loose-fitting lightweight clothing and a hat when forced to venture outside. The worst affected people in all areas affected by the Indian heat wave have been the poorest members of society, particularly in urban areas where a large number of homeless people typically sleep in the open and have no access to shelter from the heat, and poor workers who cannot afford to take time off from jobs which require hard physical exertion in the direct sun.

A man being treated for heat stroke in an Indian hospital. EPA.

The severity of the 2015 Indian heat wave appears to be related to a strong El Niño affect recorded over the southern Pacific Ocean this year. The El Niño is the warm phase of a long-term climatic oscillation affecting the southern Pacific, which can influence the climate around the world. The onset of El Niño conditions is marked by a sharp rise in temperature and pressure over the southern Indian Ocean, which then moves eastward over the southern Pacific. This pulls rainfall with it, leading to higher rainfall over the Pacific and lower rainfall over (amongst other places) India. This reduced rainfall during the already hot and dry Indian Summer leads to soaring temperatures, particularly over the eastern part of the country. Worryingly climatic predictions for the next century suggest that global warming could lead to more frequent and severe El Niño conditions, making such Indian heat waves a common occurrence.

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At keast six dead as Cyclone Huhud hits Indian east coast.
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Two killed by dust storms in Uttar Pradesh, India.
Two people have died in separate incidents in the Barabanki District of Uttar Pradesh, India, after the area was struck by severe dust storms on 28 June...

At least seven dead following heavy rains in Guwahati, Assam.
At least seven people have died following torrential rainfall overnight in the city of Guwahati in Assam State, northeast India. Three people from one family were killed and another injured when a...

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Friday 29 May 2015

Magnitude 3.0 Earthquake off the coast of Caernarfon, North Wales.

The British Geological Survey recorded a Magnitude 3.0 Earthquake at a depth of 9 km, off the east coast of Caernarfon in Gwynedd, North Wales, slightly after 2.40 pm British Summertime (slightly after 3.40 9m GMT) on Tuesday 26 May 2015. An Earthquake of this size is not dangerous, and is highly unlikely to have caused any damage or injuries, but on this occasion was felt across Anglesey, on the Lleyn Peninsula and parts of Conwy.

The approximate location of the 26 May 2015 Caernarfon 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.

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. 

(Top) Simplified diagram showing principle of glacial rebound. Wikipedia. (Bottom) Map showing the rate of glacial rebound in various parts of the UK. Note that some parts of England and Wales show negative values, these areas are being pushed down slightly by uplift in Scotland, as the entire landmass is quite rigid and acts a bit like a see-saw. Climate North East.

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.

See also...

The British Geological Survey recorded a Magnitude 1.5 Earthquake at a depth of 10 km, about 2 km to the west of...

The British Geological Survey recorded a Magnitude 1.0 Earthquake at a depth of 12 km in northeast Gwynedd, North Wales, slightly after 10.30 pm British...

The British Geological Survey recorded a Magnitude 0.9 Earthquake at a depth of 11 km in eastern Gwynedd County, North Wales, slightly before 1.25 am GMT on Thursday 26 December...

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