Saturday, 24 March 2018

Magnitude 5.2 Earthquake in the Afar Region of Ethiopia.

The United States Geological Survey recorded a Magnitude 5.2 Earthquake at a depth of 10.0 km, in the northern part of the Afar Region of Ethiopia, slightly before 1.30 pm local time (slightly before 10.30 am GMT) on Saturday 24 March 2018. There are no reports of any damage or injuries arising from this quake, but it was feltlocally, and it is possible that some minor damage has occurred.

The approximate location of the 24 March 2018 Ethiopian Earthquake. USGS.

The deserts of Northern Ethiopia and Southern Eritrea are extremely volcanically active, with dozens of volcanoes fed by an emerging divergent margin along the East African Rift; Erta Ale is on the Ethiopian Rift, the boundary between the Nubian Plate and the Danakil Microplate. The African Plate is slowly splitting apart along the Ethiopian Rift and the East African Rift to the south (which is splitting the Nubian Plate to the West from the Somali Plate to the East). Arabia was a part of Africa till about thirty million years ago, when it was split away by the opening of the Red Sea Rift (part of the same rift system), and in time the Ethiopian and East African Rifts are likely to split Africa into a number of new landmasses. 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, creating shocks that we experience as Earthquakes.

Rifting in East Africa. The Danakil Microplate is the red triangle to the east of the Afar depression at the southern end of the Red Sea. Università degli Studi di Firenze.

Witness accounts of Earthquakes can help geologists to understand these events, and the structures that cause them. The international non-profit organisation Earthquake Report is interested in hearing from people who may have felt this event; if you felt this quake then you can report it to Earthquake Report here.
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Reconstructing the locomotion of the Triassic Archosauromorph Tanystropheus.

The Tanystropheidae are a curious group of Triassic Archosauromophs (animals more closely related to Dinosaurs and Crocodiles than to Lizards and Snakes), which had a sprawling gait similar to that of modern Lizards or Crocodiles, combined with a slender body and an exceptionally long neck. This neck was comprised of a low number of greatly elongated vertebrae, thirteen in members of the genus Tanystropheus, in a similar way to that of modern Giraffes, suggesting that they had rather limited neck movement, which has made it difficult to understand the living ecology of these animals.

In a paper published in the journal Rivista Italiana di Paleontologia e Stratigrafia on 14 March 2018, Silvio Renesto of the Dipartimento di Scienze Teoriche ed Applicate at the Università degli Studi dell’Insubria, and Franco Saller of Gargazzone in the South Tyrol, re-examine the skeletal morphology of Tanystropheus, with a view to understanding its movement and therefore potentially its ecology.

Reconstruction of the skeleton of a large specimen of Tanystropheus longobardicus in walking posture. Scale bar equals 1m. Renesto & Saller (2018).

A specimen of Tanystropheus with hooklets from Belemnoid Cephalopod was discovered in the 1970s, leading to speculation that the animal may have been a swimming predator, similar to the later Elasmosaurs, but Tanystropheus lacked the musculature for constant swimming, making such a lifestyle impossible. Another suggestion was that it may have hunted in a similar way to a Heron, remaining motionless on the shore or in shallow water, and striking at prey with its long neck, but the neck of the animal was apparently to inflexible to allow for such a mode of life.

Renesto and Saller re-examined the skeleton of Tanystropheus, and observed that the hindlegs were considerably longer than the hindlimbs, and that the hindquaters and tail appear to have been much more heavily muscled than the rest of the body, which they suggest implies that the hindlinbs and tail were the main drivers of locomotion in the living animal.

Tanystropheus longobardicus (A) transversal  section the base of  the tail with reconstruction of the pattern of the muscles; (B) transversal section at mid tail; (C) reconstruction of the development of the caudofemoralis longus in ventral view; (D) reconstruction of the caudofemoralis longus (dark grey) and ilioischioocaudalis (light grey) in lateral view; (E) path of the main leg muscles in Tanystropheus. Abbreviations in (E): cfb, caudofemoralis brevis, ft, femorotibialis, g, gastrocnemius, ife, iliofemoralis, ifi, iliofibularis, pife, puboischiofemoralis. Renesto & Saller (2018).

Due to the elongate body of Tanystropheus, any form of locomotion relying on alternate strokes of the hindlimbs would probably have been extremely unstable, however if the hindlimbs were pulled forward to their full extent and then pushed back simultaneously, then they could have delivered a powerful backward kick, enabling the animal to push off the shore or another vantage point, or drive a short burst of powerful swimming.

Sketch representing Tanystropheus diving quickly into water by symmetrical stroke of the hind limbs starting from resting position. Renesto & Saller (2018).

Renesto and Saller suggest that this motion would have made Tanystropheus an effective ambush predator, able to strike rapidly at aquatic prey from either the shore or a vantage point in the water, with its small head and slender neck disguising its true size from its prey until a stroke of the hindlimbs drove it forward rapidly in a striking motion.

Reconstruction of Tanystropheus swimming in shallow sea. Renesto & Saller (2018).

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Lepidochelys olivacea: Olive Ridley Turtles colonise Mumbai beach.

Around eighty hatchling Olive Ridley Turtles, Lepidochelys olivacea, were observed crawling down Versova Beach in Mumbai on Thursday 22 March 2018, prompting a search by volunteers who found a nest site on Friday 23 March. The coast of Maharashtra State, India, is thought to provide nesting sites for about 600 Olive Ridleys, but they are not usually found on Mumbai's heavily polluted beaches. However Versova Beach has been the subject of a cleanup campaign by a the Versova Residents Volunteers, a community-led environmental group which has removed about 13 million kg of plastic and other materials since 2015. The last report of a Turtle nest in Mumbai was over 20 years ago, though this was not photographed or observed by scientists and is generally regarded as apocryphal. An injured Olive Ridley was found on Juhu Beach in Mumbai, and treated by a local vet, but it is not thought that this Turtle was nesting.

Hatchling Olive Ridley Turtles on Versova Beach, Mumbai, on 22 March 2018. Afroz Shah/Versova Residents Volunteers.

Olive Ridleys are the smallest, and most abundant, species of Sea Turtles, though they are still considered to be Vulnerable under the terms of the International Union for the Conservation of Nature's Red List of Threatened Species, due to the threat posed to their breeding grounds by Human activity, and the (now illegal) trade in meat, eggs and leather from these Turtles. The species is slow to colonise new nesting areas, as females usually return to the beaches where they were born to lay eggs. In India the species has been the subject of a deliberate re-introduction scheme in Orissa Stste, but the colonisation of a beach in Mumbai is both unexpected and welcomed by environmentalists.

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Charax awa: A new species of Charicid Fish from Maranhão State in northestern Brazil.

Charicids are freshwater Boney Fish related to Piranhas and Tetras that are found across South and Central America and as far north as Mexico and parts of Texas. Members of the genus Charax are medium sized members of this group, reaching a maximum of about 130 mm in length, most abundant in the Andean regions, but also found in southern and western Brazil and parts of the Guyanan Shield. No described member of this genus has a distribution that includes the coastal basins of northeastern Brazil, but there are several records of Fish apparently belonging to this group being found there. 

In a paper published in the journal Zoosystematics and Evolution on 1 February 2018, Erick Cristofore Guimarães of the Programa de Pós-Graduação em Biodiversidade e Conservação, and the Laboratório de Sistemática e Ecologia de Organismos Aquáticos at the Universidade Federal do Maranhão, Pâmella Silva De Brito of the Programa de Pós-Graduação em Biodiversidade e Biotecnologia da Amazônia and the Laboratório de Sistemática e Ecologia de Organismos Aquáticos at the Universidade Federal do Maranhão, Beldo Rywllon Abreu Ferreira, also of the Programa de Pós-Graduação em Biodiversidade e Conservação at the Universidade Federal do Maranhão, and Felipe Polivanov Ottoni, of the Programa de Pós-Graduação em Biodiversidade e Conservação, the Programa de Pós-Graduação em Biodiversidade e Biotecnologia da Amazônia, the Laboratório de Sistemática e Ecologia de Organismos Aquáticos, and the Programa de Pós-Graduação em Oceanografia at the Universidade Federal do Maranhão, describe a new species of Charax from the Rio Mearim, Rio Munim and Rio Turiaçu basins, of Maranhão State in northestern Brazil.

The new species is named Charax awa, where ‘awa’ is the name used by the Guajá people of Maranhão State to describe themselves. Adults of this species range from 40.2 to120.0 mm in length and are silvery in colour, darker on the upper surface and towards the front, and with blotchy markings on the fins. The upper part of the head is distinctly concave, and the eyes somewhat small. The upper and lower jaws both have enlarged canine teeth as well as rows of smaller, conical teeth. 

 Charax awa, live specimen from a stream at the Miranda do Norte, in the Mearim River Basin of Maranhão State, Brazil. Erick Guimarães in Guimarães et al. (2018).

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Asteroid 2018 FD2 passes the Earth.

Asteroid 2018 FD2 passed by the Earth at a distance of about 907 000 km (2.36 times the average distance between the Earth and the Moon, or 0.61% of the distance between the Earth and the Sun), slightly after 6.35 am GMT on Saturday 17 March 2018. There was no danger of the asteroid hitting us, though were it to do so it would not have presented a significant threat. 2018 FD2 has an estimated equivalent diameter of 8-26 m (i.e. it is estimated that a spherical object with the same volume would be 8-26 m in diameter), and an object of this size would be expected to explode in an airburst (an explosion caused by superheating from friction with the Earth's atmosphere, which is greater than that caused by simply falling, due to the orbital momentum of the asteroid) in the atmosphere between 35 and 25 km above the ground, with only fragmentary material reaching the Earth's surface.

The calculated orbit of 2018 FD2. Minor Planet Center.

2018 FD2 was discovered on 19 March 2018 (two days after its closest approach to the Earth) by the University of Arizona's Catalina Sky Survey, which is located in the Catalina Mountains north of Tucson. The designation 2018 FD2 implies that it was the 54th asteroid (asteroid D2) discovered in the second half of March 2018 (period 2018 F).
2018 FD2 has a 434 day orbital period and an eccentric orbit tilted at an angle of 14.8° to the plane of the Solar System, which takes it from 0.68 AU from the Sun (i.e. 68% of he average distance at which the Earth orbits the Sun, and inside the orbit of the planet Venus) to 1.59 AU from the Sun (i.e. 159% of the average distance at which the Earth orbits the Sun, and slightly outside the orbit of the the planet Mars). It is therefore classed as an Apollo Group Asteroid (an asteroid that is on average further from the Sun than the Earth, but which does get closer). This means that 2018 EB4 has occasional close encounters with the planet Earth, with the last thought to have occurred in September 2016.

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Stictosisyra pennyi: A new species of Sisyrid Lacewing from Cretaceous Burmese Amber.

Sisyrid Lacewings, Sisyridae, are a small group of Neuropteran Insects today, with about 70 living species in four genera, mostly living in tropical areas. Based upon their relationships to other Neuropterans, Sisyrids are thought likely to be an ancient group, but they have only a limited fossil record, with six described fossil species, all from Eurasia. The oldest of these fossil species, Paradoxosisyra groehni, comes from Middle-to-Late Cretaceous Burmese Amber, from Kachin State in Myanmar, and is considered to be sufficiently different from all other known Sisyrids, living and fossil, to place it in a separate subfamily, the Paradoxosisyrinae.

In a paper published in the journal ZooKeys on 23 February 2018, Qiang Yang of the State Key Laboratory of Biocontrol at Sun Yat-sen University, the College of Life Sciences at Capital Normal University, and the Geoscience Museum at Hebei GEO University, Chaofan Shi, also of the College of Life Sciences at Capital Normal University, and the School of Earth Sciences and Engineering at Sun Yat-sen University, Dong Ren and Yongjie Wang, again of the College of Life Sciences at Capital Normal University, and Hong Pang, also of the State Key Laboratory of Biocontrol at Sun Yat-sen University, describe a second species of Sisyrid from Cretaceous Burmese Amber.

Cretaceous ‘Burmese Amber’ has been extensively worked at several sites across northern Myanmar (though mostly in Kachin State) in the last 20 years. The amber is fairly clear, and often found in large chunks, providing an exceptional window into the Middle Cretaceous Insect fauna. This amber is thought to have started out as the resin of a Coniferous Tree, possibly a Cypress or an Araucaria, growing in a moist tropical forest. This amber has been dated to between 105 and 95 million years old, based upon pollen inclusions, and to about 98.8 million years by uranium/lead dating of ash inclusions in the amber. 

The new species is named Stictosisyra pennyi, where ‘Stictosisyra’ means ‘speckled Sisyrid’ in reference to a pattern of markings on its forewing, and ‘pennyi’ honours the late Norman Penny for his work on Lacewings and is kindness to Qiang Yang and Chaofan Shi during a visit to the California Academy of Sciences in 2016. The species is named from a single male specimen 2.9 mm in length. This specimen lacks the highly specialized mouthparts seen in Paradoxosisyra groehni, but is nevertheless thought to be more closely related to that species than to any other Sisyrid, living or fossil, and is therefore placed in the Paradoxosisyrinae.

Stictosisyra pennyi, male specimen, (A) photograph and (B) drawing. Scale bars are 1 mm. Yang et al. (2018). 

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Friday, 23 March 2018

Sinkholes swallow car and undermine building in the Centurian area of Gauteng Province, South Africa.

A series of sinkholes have opened up in the Centurian area of Gauteng Province, South Africa (between Pretoria and Midrand), following heavy rains in the area. In Valhala, on Friday 23 March 2017, Mpho Borodi, 30, drove into a sinkhole on an unlit road while on his way to work, while a second driver, had her car trapped as a sinkhole opened up beneath it. In Lyttelton a commercial building was partially undermined by another sinkhole, though the Tshwane Metro Geology Department had apparently previously warned that the building was at risk, while in Makause a number of families have been forced to evacuate their homes due to a nearby sinkhole which has put them at risk.

Car trapped in a sinkhole in Valhala, Gauteng, on 23 March 2018. Centurian Rekord.

Sinkholes are generally caused by water eroding soft limestone or unconsolidated deposits from beneath, causing a hole that works its way upwards and eventually opening spectacularly at the surface. Where there are unconsolidated deposits at the surface they can infill from the sides, apparently swallowing objects at the surface, including people, without trace.

 Building undermined by a sinkhole in Lyttleton, Gauteng, on 22 March 2018. Centurian Rekord.

On this occasion the sinkholes have been linked to heavy rains in the area, with over 120 mm of rain recorded in Pretoria in 24 hours, which has caused a series of flash floods in Centurian, Pretoria, Johannesburg and neighbouring parts of Gauteng‚ KwaZulu-Natal and the Free State Provinces. The immediate causes of the sinkholes have not yet been determined, but it is thought that in several cases soft sediment beneath roads has been swept away after storm drains became blocked by vegetation and other debris causing water to escape into the surrounding deposits.

Flash flood in Bryanston, Gauteng, on 23 March 2018. Eyewitness News.

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