Thursday, 19 July 2018

Platythyrea janyai: A new species of Ant from southern Thailand and western Malaysia.

The genus Platythyrea currently contains 38 species of large stinging Ants from tropical regions of the Americas, Australia, Africa and East Asia, which nest in cavities in live or dead trees (or in the case of some African species, Termite mounds). In all species in this genus in which reproduction has been studied, the workers are able to reproduce parthogenically (i.e. workers can lay eggs which produce clones of themselves), with some species also producing sexual queens and males.

In a paper published in the journal ZooKeys on 16 January 2018, Natthaporn Phengsi of the Department of Biology at Burapha University, Weeyawat Jaitrong of the Natural History Museum in Khlong Luang, Jiraporn Ruangsittichai of the Department of Medical Entomology at Mahidol University, and Salinee Khachonpisitsak, also of the Department of Biology at Burapha University, describe a new species of Platythyrea from southern Thailand and western Malaysia.

The new species is named Platythyrea janyai, in honour of Janya Jareanrattawong of the Royal Forest Department of Thailand, for his help with collecting the specimens from which the species is described. The specie is described from four workers collected from dead wood on the forest floor in lowland rainforest in the Khao Pu Khao Ya National Park in Phatthalung Province in southern Thailand; the species was also observed in the Khao Chong Botanical Garden in Trang Province, also southern Thailand, and in the Ulu Gombak Forest Reserve in Selangor State, Malaysia. The described specimens are between 6.63 and 6.96 mm in length, and are dark brown in colour, with reddish and yellowish markings.

Platythyrea janyai, worker. (A) Body in profile view. (B) Head in full-face view. (C) Body in dorsal view. Phengsi et al. (2018).

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Magnitude 5.7 Earthquake in Oaxaca State, Mexico.

The United States Geological Survey recorded a Magnitude 5.7 Earthquake at a depth of 55.4 km, approximately 1 km to the northwest of the city of Huajuapan de Leon in Oaxaca State, Mexico, slightly after 8.30 am local time (slightly after 1.30 pm GMT) on Thursday 19 July 2018. This even was felt across much of southern and central Mexico, but there are no reports of any damage or casualties.

The approximate location of the 19 July 2018 Oaxaca Earthquake. USGS.

Mexico is located on the southernmost part of the North American Plate. To the south, along the Middle American Trench, which lies off the southern coast off Mexico, the Cocos Plate is being subducted under the North American Plate, passing under southern Mexico as it sinks into the Earth. This is not a smooth process, and the plates frequently stick together then break apart as the pressure builds up, causing Earthquakes on the process.

The Cocos Plate is thought to have formed about 23 million years ago, when the Farallon Plate, an ancient tectonic plate underlying the East Pacific, split in two, forming the Cocos Plate to the north and the Nazca Plate to the south. Then, roughly 10 million years ago, the northwesternmost part of the Cocos Plate split of to form the Rivera Plate, south of Beja California.

 The position of the Cocos, Nazca and Rivera Plates. MCEER/University at Buffalo.

In a paper published in the Journal of Geophysical Research, in 2012, a team led by Igor Stubailo of the Department of Earth and Space Sciences at the University of California Los Angeles, published a model of the subduction zone beneath Mexico using data from seismic monitoring stations belonging to the Mesoamerican Seismic Experiment, the Network of Autonomously Recording Seismographs, the USArray, Mapping the Rivera Subduction Zone and the Mexican Servicio Sismologico Nacional.
The seismic monitoring stations were able to monitor not just Earthquakes in Mexico, but also Earthquakes in other parts of the world, monitoring the rate at which compression waves from these quakes moved through the rocks beneath Mexico, and how the structure of the rocks altered the movement of these waves.
Based upon the results from these monitoring stations, Stubailo et al. came to the conclusion that the Cocos Plate was split into two beneath Mexico, and that the two plates are subducting at different angles, one steep and one shallow. Since the rate at which a plate melts reflects its depth within the Earth, the steeper angled plate melts much closer to the subduction zone than the shallower angled plate, splitting the Trans-Mexican Volcanic Belt into sections above the different segments of the Cocos Plate, and causing it to apparently curve away from the subduction zone.
 Top the new model of the Cocos Plate beneath Mexico, split into two sections (A & B) subducting at differing angles. (C) Represents the Rivera Plate, subducting at a steeper angle than either section of the Cocos Plate. The Split between the two has been named the Orozco Fracture Zone (OFZ) which is shown extended across the Cocos Plate; in theory this might in future split the Cocos Plate into two segments (though not on any human timescale). Bottom Left, the position of the segments on a map of Mexico. Darker area is the Trans-Mexican Volcanic Belt, orange circles are volcanoes, brown triangles are seismic monitoring stations, yellow stars are major cities. Bottom Right, an alternative model showing the subducting plate twisted but not split. This did not fit the data. Stubailo et al. (2012).
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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Wednesday, 18 July 2018

Astronomers discover twelve new moons orbiting Jupiter.

Until this month Jupiter was known to have sixty seven moons, split into three separate groups. Firstly their are the four large Galilean Moons  discovered by Galileo Galilei in January 1610, which are larger than both Earth's Moon and the planet Mercury, and which orbit in the same direction and plane as the planet rotates. Secondly their are the smaller prograde moons, which also orbit in the same plane and direction as the rotation of the planet; these are split into two groups, the four Inner Moons, which orbit inside the orbits of the Galilean Moons, and the larger group of Himalian Moons, which orbit outside (and take their name from the moon Himalia, the largest member of the group). Finally there are the retrograde moons, which orbit some way outside the prograde moons, in roughly the same plane but in the oposite direction, split into three distinct families, Carme, Ananke, and Pasiphae, which are thought to have derived from three separate parent moons which broke up at some time in the remote past.

On 16 June 2018 a team led by Scott Shepard of the Carnegie Institution for Science, announced the discovery of twelve new moons of Jupiter, discovered by the Cerro Tololo Inter-American Observatory on Chile between 2016 and 2018. 

Two of these moons,  S/2017 J4 and S/2018 J1 (designations which imply the forth Jovian Moon discovered in 2017 and the first discovered in 2018) are placed within the Himalian Group. Four, S/2017 J7, S/2016 J1, S/2017 J3, and S/2017 J9, are placed within the Anake Group, two, S/2017 J6 and S/2017 J1, are placed within the Pasiphae Group, while three more, S/2017 J5, S/2017 J8 and S/2017 J2, are placed within the Carne Group. The final new discovery, S/2016 J2, however, is distinct from any previously discovered population of Jovian Moons, with a prograde orbit tilted at an angle of 34° to the plane of the Jovian system, and outside the orbit of the Himalia Group, on an orbit that overlaps that of the Retrograde Moons. This orbit is so distinctive that the moon has been given a provisional formal name, Valetudo (after a great grandaughter of the Roman god Jupiter).

Illustration showing the newly discovered moon (in green). Roberto Molar Candanosa/Carnegie Institute.

S/2016 J2 Valetudo orbits Jupiter at an average distance of 18 938 000 km (roughly fifty times the distance at which our Moon orbits the Earth), and is about a kilometre in diameter.

Recovery images of Valetudo from the Magellan Telescope in May 2018.  The moon can be seen moving relative to the steady state background of distant stars.  Jupiter is not in the field but off to the upper left. Carnegie Institute.

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Tourists injured after lava bomb strikes boat by coast of Hawai'i.

Twenty three people have been injured, three of them seriously, after a lava bomb (chunk of lava thrown from a volcano, in either liquid or solid form) from Mount Kilauea struck a tour boat of the coast of Hawai'i on Monday 16 July 2018. The volcano began erupting from a new fissure on its eastern flank on 3 May 2018, since when a series of fissures have opened up, producing several major lava flows, which have destroyed many homes and other properties, and at least one of which has reached the sea, producing a laze (toxic haze resulting from hot lava hitting water, producing chemical-laden steam, which had led to the U.S. Coast Guard imposing a 50 m exclusion zone around areas of the coast that were being reached by the lava, though the boat struck by the lava bomb despite being outside this zone.

Damage to a tourist boat struckby a lava bomb off the coast of Hawai'i on 16 July 2018. Hawai'i Department of Land and Natural Resources.

The islands of Hawai'i have formed as a result of hotspot volcanism, with a mantle plume hotspot currently located under Big Island, Hawai'i, and each of the other islands being the result of previous activity from the same hotspot, with the oldest Islands in the northwest and newest in the southeast. A volcanic hotspot is an area where magma from deep inside the Earth is welling up through the overlying plate (in this case the Pacific) to create volcanism at the surface. Volcanoes move as they erupt, swelling as magma enters their chambers from bellow, then shrinking as that magma is vented as lava.

 The position of the Hawai'i Hotspot relative to the islands of Hawai'i. Joel Robinson/USGS/Wikimedia Commons.

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Tuesday, 17 July 2018

Micromammals from Byzantine agricultural sites in the Negev Desert.

The Negav Desert, in fact a mixture of desert and semi-desert terrains, covers an area of about 13 000 km² in southern Israel. The area has an agricultural economy today, reliant on extensive irrigation projects and modern industrial farming methods, but for most the history of Human settlement in the area has been considered to arid for extensive farming. However, during the Byzantine Period, roughly 300-700 AD, an extensive system of terraced farming, and accompanying irrigation systems was present in the area, probably associated with a slightly wetter climate. Such an agricultural system is likely to have had a profound effect on local landscapes and ecosystems, though relatively little is understood about this.

In a paper published in the journal Royal Society Open Science on 10 January 2018, Tal Fried, Lior Weissbrod, Yotam Tepper and Guy Bar-Oz of the Zinman Institute of Archaeology at the University of Haifa describe the results of a series of excavations at dovecotes at Byzantine settlements in the Negev, in which sediments were sifted for micromammal remains, in order to understand the nature of small Mammal communities in the area during this period.

Dovecotes are a common feature in Byzantine settlements in the Negev, and are thought to have been used to produce not just Pigeon, Columba livia, meat and eggs, but also fertiliser for fields in areas where the soil was often very poor. The structures excavated were identified as dovecotes by the large amounts of both Pigeon bones and dung present, and were from two separate settlements, Shivta and Sa’adon.

Fried et al. found the micromammal communities of the Byzantine Period in the Negev Desert were dominated by Gerbils, Gerbillus spp., and Jirds, Meriones spp , (together Gerbilids), with a variety of other species present, including Lesser Egyptian Jerboa, Jaculus jaculus, House Mouse, Mus musculus domesticus, Asian Garden Dormouse, Eliomys melanurus, Black Rat, Rattus rattus, Mole Rat, Spalax ehrenbergi, Sand Rat, Psammomys obesus, White Toothed Shrew, Crocidura sp., and Etruscan Shrew, Suncus etruscus. All of these bones were from juvenile or young adult individuals, and many showed signs of acid digestion, consistent with having spent time in the stomach of an Owl of other Bird of Prey, suggesting that they had not actually been living in the Dovecotes but in the surrounding area.

Typical digestion marks on skeletal remains of micromammals from the structure A dovecote in Sa’adon on elements of the femur (a,b,d,e), mandible (c) and tibia (f ). Fried et al. (2018).

All of these species are present in the Negev today, but with rather different distributions. Modem micromammal communities around agricultural settlements are dominated by Mice and Rats, whereas both Gerbils and Jirds are found in more arid areas away from Human settlements, with Gerbils favouring sandy soils and Jirds favouring loess soils. 

Fried et al.'s data seems to suggest that Byzantine agriculture provided a more suitable environment for Gerbilids than modern farms (probably suggesting that they were on the whole drier than the modern farms). However the population size of Rats and Mice does appear to have been slightly larger than that in the same area both before and after the settlements were present, indicating the presence of these farms did make the desert more suitable for these species than it was in its untamed state.

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Sunday, 15 July 2018

Fifteen confirmed deaths following landslide at Myanmar jade mine.

Fifteen people are known to have died and at least 45 more have been injured following a landslide at a jade mine near Hpakant in Kachin State, Myanmar, on Saturday 14 July 2018. The incident occurred on a spoil heap, where people were scavenging for any jade that may have been missed by the mine-operators, and it is feared that others may be unaccounted for in this incident as spoil-heap workers, known as Yay Ma Say, are often reluctant to discuss their activities with outsiders, even rescue workers, due to the legally dubious nature of the work.

A jade mining area near Hpakant in Kachin State, Myanmar. The mining is an open cast process, which results in numerous spoil heaps, which are searched by informal workers hoping to find fragments of jade. Reuters.

Myanmar is the world's largest producer of jade, though much of this is produced (along with other precious and semi-precious minerals such as amber) at unregulated (and often illegal) artisanal mines in the north of the country, from where it is smuggled into neighbouring China. Accidents at such mines are extremely common, due to the more-or-less total absence of any safety precautions at the site. At many sites this is made worse by the unregulated use of explosives to break up rocks, often leading to the weakening of rock faces, which can then collapse without warning. The majority of people in this industry are migrant workers from the surrounding countryside, not registered with any local authority, which can make it difficult for rescuers to identify victims following such events, or even gain accurate assessments of the number of people likely to have been involved in such accidents.

The incident occurred following several hours of rain in the area associated with the Southeast Asian Southwest Monsoon, which has also caused a series of landslips and flash floods in the area. Landslides are a common problem after severe weather events, as excess pore water pressure can overcome cohesion in soil and sediments, allowing them to flow like liquids. Approximately 90% of all landslides are caused by heavy rainfall. This year's monsoon has been particularly severe, with floods and landslips occurring across Myanmar.

The approximate location of the town of Hpakant. Google Maps.

 Monsoons are tropical sea breezes triggered by heating of the land during the warmer part of the year (summer). Both the land and sea are warmed by the Sun, but the land has a lower ability to absorb heat, radiating it back so that the air above landmasses becomes significantly warmer than that over the sea, causing the air above the land to rise and drawing in water from over the sea; since this has also been warmed it carries a high evaporated water content, and brings with it heavy rainfall. In the tropical dry season the situation is reversed, as the air over the land cools more rapidly with the seasons, leading to warmer air over the sea, and thus breezes moving from the shore to the sea (where air is rising more rapidly) and a drying of the climate.

 Diagrammatic representation of wind and rainfall patterns in a tropical monsoon climate. Geosciences/University of Arizona.

Much of Southeast Asia has two distinct Monsoon Seasons, with a Northeast Monsoon driven by winds from  the South China Sea that lasts from November to February and a Southwest Monsoon driven by winds from the southern Indian Ocean from March to October. Such a double Monsoon Season is common close to the equator, where the Sun is highest overhead around the equinoxes and lowest on the horizons around the solstices, making the solstices the coolest part of the year and the equinoxes the hottest. However Myanmar is largely protected from the Northeast Monsoon by the mountains separating the country from Yunnan Province in China.
 The winds that drive the Northeast and Southwest Monsoons in Southeast Asia. Mynewshub.
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