Monday, 16 January 2017

Magnitude 5.7 Earthquake in North Sumatra.

The United States Geological Survey recorded a Magnitude 5.7 Earthquake at a depth of 10 km, about 18 km to the northeast of the town of Kabanjahe in North Sumatra Province, Indonesia slightly after 7.40 pm Western Indonesian Time (slightly after 12.40 pm GMT) on Monday 16 January 2017. There are no reports of any damage or casualties associated with this quake, but people have reported feeling it across North Sumatra and Peninsula Malaysia.

The approximate location of the 16 January 2017 Earthquake. USGS.

The Indo-Australian Plate, which underlies the Indian Ocean to the west of Sumatra, is being subducted beneath the Sunda Plate, a breakaway part of the Eurasian Plate which underlies Sumatra and neighbouring Java, along the Sunda Trench, passing under Sumatra, where friction between the two plates can cause Earthquakes. As the Indo-Australian Plate sinks further into the Earth it is partially melted and some of the melted material rises through the overlying Sunda Plate as magma, fuelling the volcanoes of Sumatra.

 The Subduction zone beneath Sumatra. NASA/Earth Observatory.

This does not happen at a 90° angle, as occurs in the subduction zones along the western margins of North and South America, but at a steeply oblique angle. This means that as well as the subduction of the Indo-Australian plate beneath the Sunda, the two plates are also moving past one-another. This causes rifting within the plates, as parts of each plate become stuck to the other, and are dragged along in the opposing plate's direction. The most obvious example of this is the Sumatran Fault, which runs the length of Sumatra, with the two halves of the island moving independently of one-another. This fault is the cause of most of the quakes on the island, and most of the island's volcanoes lie on it.

 The movement of the tectonic plates around Sumatra. NASA/Earth Observatory.

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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Sunday, 15 January 2017

Preserved Trilobte eggs from the Ordovician of New York State.

Trilobites are the most abundant Arthropods in Palaeozoic deposits, and have been extensively studied form many years. Much of their biology is now well understood, but their reproductive method remains mysterious, with historic claims of copulating Trilobites not taken seriously and claims that structures found unassociated with adult Trilobites are Trilobite eggs impossible to verify. This is a pity, since Trilobites were among the first Arthropods to appear, and an understanding of their reproductive biology could potentially help us to understand the ancestral state in all Arthropods.

In a paper published in the journal Geology on 9 January 2016, Thomas Hegna of the Department of Geology at Western Illinois University, Markus Martin of Watertown in New York and Simon Darroch of the Department of Earth and Environmental Sciences at Vanderbilt University describe in situ eggs associated with the Trilobite Triarthrus eatoni, from the Ordovician Whetstone Gulf Formation at Martin Quarry in New York State.

The eggs were found associated with two Trilobite specimens examined with the North Star Imaging micro-CT scanner housed at Vanderbilt University. This revealed the presence of a series of ovoid structures 159–177 μm in length located on the underside of cephala of the Trilobites. This is similar to the situation in Horseshoe Crabs, the closest living relatives of Trilobites, in which unfertilised eggs are released from a prosomal ovarian network within the head. Several alternative explanations for the objects were considered, however it was thought that they were too large to be preserved microbes, and are in an unlikely location for fecal pellets, small epibionts or localised pyrite growth.

Pyritized specimens of Triarthrus eatoni from the Ordovician Whetstone Gulf Formation (Lorraine Group), upstate New York (USA). (A) Ventrally preserved specimen (Yale Peabody Museum [YPM] 535703) showing nine eggs in the specimen’s left genal angle. (B) Ventrally preserved specimen (YPM 535704) showing four eggs in the specimen’s right genal angle. (C) Close-up of the egg-bearing region from the specimen in (B). (D) Close up of the egg-bearing region from the specimen in (A). (E) Scanning electron microscopy (SEM) image of the eggs from the specimen in (A) and (D). Note that the perspective is twisted ~180° from that in (D). (F) SEM image of an egg from (E). (G) Close-up SEM image of the egg surface from (F). Note the dominant framboids and rare euhedral crystals of pyrite. (H) Close-up of a limb from (A). Note the dominant framboids and rare euhedral crystals of pyrite. (I) SEM image of a disarticulated cranidium (YPM 238366) that was replaced with pyrite. (J) SEM image showing the replacement fabric from (I). Note the dominant euhedral crystals of pyrite. (K)–(M) Dorsal digital reconstruction of the specimen in (A) derived from microcomputed tomography scan data. (L) Ventral reconstruction. (M) Left-ventral reconstruction. Scale bars in (A) and (B) are 5 mm long; scale bars in (C) and (D) are 2 mm long. Hegna et al. (2016).

The presence of eggs in the cephala of Trilobites suggests a similat method of reproduction to that in Horseshoe Crabs, with males clustering around the females as they secrete eggs in order to fertilise them externally. This is consistent with the known anatomy of Trilobites and other Palaeozoic Arthropods in which (with the exception of Eurypterids) in which external genitalia have never been found. Hegna et al. note that a number of recent finds of Palaeozoic Arthropods have shown external brooding of the young. This has led to suggestions that this may have been the most common form of reproduction in early Arthropods, and even the original breeding strategy in the group. However they observe that almost all Palaeozoic Arthropods are preserved by pyritization, which preserves only the external form of the specimens, and is subsequently unlikely to preserve other reproductive strategies such as internal brooding.

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Magnitude 5.2 Earthquake off the west coast of Colombia.

The United States Geological Survey recorded a Magnitude 5.2 Earthquake at a depth of 6 km approximately 60 km off the west coast of Colombia, at slightly after 4.05 -m local time (slightly after 11.05 am GMT) on Thursday 12 January 2017. There are no reports of any damage or casualties associated with this event, but people reported feeling the event in parts of Panama.

The approximate location of the 12 January 2016 Colombia Earthquake. USGS.

Colombia is on the west coast of South America and the western margin of the South American Plate, close to where the Nazca Plate, which underlies part of the east Pacific, is being subducted along the Peru-Chile Trench. The Nazca Plate passes under the South American Plate as it sinks into the Earth, this is not a smooth process and the plates repeatedly stick together then break apart as the pressure builds up, causing Earthquakes. As the Nazca Plate sinks further it is partially melted by the friction and the heat of the Earth's interior. Some of this melted material then rises through the overlying South American Plate, fuelling the volcanoes of Colombia and neighbouring countries.

The subduction of the Nazca Plate beneath the South American Plate, and how it causes Earthquakes and volcanoes. SIO SEARCH.

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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Collapse at illegal coal mine kills at least four in West Bengal.

At least four miners are reported to have died and several more are reportedly missing, following a collapse at an illegal coal mine in West Bengal, India. The incident happened at a mine in the village of Kalikapur in Bankura District on Thursday 12 January 2017, though details of the incident are unclear, as the mine's owners are reportedly refusing to co-operate with authorities. 

The approximate location of the Kalikapur mine. Google Maps.

Illegal mining (mining without due licenses and adherence to mining regulations) is a significant problem in India, where output from legal mines often fails to meet the demand of the countries burgeoning industrial and construction sectors. As well as small artisanal mines (mines operated by small individual miners or groups using traditional methods) these illegal mines can include quite large operations run by criminal organisations or semi-legal businesses. Such operators can sometimes gain political capitol from the claim that mining regulations are a colonial imposition, even where the regulations being flouted are post-colonial rules on human rights, health and safety and environmental protection.

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Asteroid 2017 AS4 passes the Earth.

Asteroid 2017 AS4 passed by the Earth at a distance of 561 900 km (1.46 times the average distance between the Earth and the Moon, 0.38% of the average distance between the Earth and the Sun), at about 5.05 pm GMT on Sunday 8 January 2017. There was no danger of the asteroid hitting us, though had it done so it would have presented no threat. 2017 AS4 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 37 and 20 km above the ground, with only fragmentary material reaching the Earth's surface. 

The calculated orbit of 2017 AS4. Minor Planet Center.

2017 AS4 was discovered on 5 January 2017 (three days before its closest approach to the Earth) by the University of Arizona's Mt. Lemmon Survey at the Steward Observatory on Mount Lemmon in the Catalina Mountains north of Tucson. The designation 2017 AS4 implies that the asteroid was the 118th object (object S4) discovered in the first half of January 2017 (period 2017 A).

2017 AS4 is calculated to have a 1184 day orbital period and an elliptical orbit tilted at an angle of 1.95° to the plain of the Solar System that takes it from 0.69 AU from the Sun (i.e. 90% of the average distance at which the Earth orbits the Sun, slightly inside the orbit if the planet Venus) to 3.68 AU from the Sun (i.e. 368% of the average distance at which the Earth orbits the Sun, considerably more than twice the distance at which the planet Mars orbits the Sun). 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 close encounters between the asteroid and Earth do happen occasionally, with the next predicted in January 2068.

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Saturday, 14 January 2017

Hoolock tianxing: A new species of Hoolock Gibbon from China and Myanmar.

Gibbons, Hylobatidae, are small Apes found across East, South and Southeast Asia. There are currently 19 species of Gibbons divided into four genera. Hoolock Gibbons, Hoolock spp., also known as Hoolocks or White-browed Gibbons, are found in the northwestern part of this total range, across parts of northeast India, Bangladesh, Myanmar and Yunnan Province, China. They are distinguished from other Gibbons by a number of genetic and morphological features, but most obviously by the presence of the distinctive white eyebrows that give the group its common name. The genus is currently split into two species, living on either side of the Chindwin River in Myanmar. Major rivers commonly provide barriers between Gibbon species, not simply because Gibbons cannot swim, but because the type of trees in river basins are not suitable environments for Gibbons. This has led to speculation that other river valleys may form barriers between undetected Gibbon species.

In a paper published in the American Journal of Primatology on 10 January 2016, a team of scientists led by Peng-Fei Fan of the School of Life Sciences at Sun Yat-sen University and Institute of Eastern-Himalaya Biodiversity Research at Dali University, describe a new species of Hoolock Gibbon from eastern Myanmar and southwestern China.

The new species is named Hoolock tianxing, where 'tianxing' means 'Skywalker' in Chinese, in reference to the unique brachiating motion of Gibbons. It was identified by morphological and genetic examination of museum specimens and living animals bred in Zoos and confiscated from smugglers, as well as photographs of wild animals and genetic material from stool specimens collected from the wild. In keeping with current Chinese law and the ethical guidelines of the American Society of Primatologists, no live animals were killed or collected during the study.

The new species can be distinguished on a number of morphological characteristics, but most obviously their fur, which is brown in the males and yellow in the females, with the white eyebrows of the males thinner and more widely spaced than in any other species and that of the females downturned and with more white between the eyes than any other species.

Male Hoolock tianxing. Fan et al. (2016).

The species was found in the areas between the Nmai Hka and Salween rivers (tributaries of the Irawady) in parts of Shan, Kayah and Kayin states in Myanmar and Yunnan Province in China. This area around Mount Gaoligong in the westernmost part of the Hengduan Mountain Chain, an extension of the Himalayas. This population has previously been thought to belong to the species Hoolok leuconedys, (the Eastern Horlook), which is considered to be Vulnerable under the terms of the International Union for the Conservation of Nature's Red List of Threatened Species, with an estimated population of 310 000–370 000 individuals. However the new species has a much more limited range and consequently a lower population. In addition it is subject to illegal hunting and destruction, degradation and fragmentation of its habitat throughout its range. It is estimated that about 200 of these Gibbons survive in China, with around 50 000 in Shan State in Myanmar and about 16 000 in Kayah and Kayin States. For this reason the new species is assessed to be Endangered under the terms of the Red List.

Female Hoolock tianxing. Fan et al. (2016).

Fan et al. also developed a genetic phylogeny for the new species, using mitochondrial genetic samples from 10 Gibbon species, two Gorilla species, two Chimpanzee species, two Orangutan species, three Macaque species, and Humans. This was given a chronological framework by the inclusion of fossil species thought to have been close to the branching points between modern lineages, namely Rukwapithecus fleaglei from the Miocene Nsungwe Formation of Tanzania, thought to be the oldest Great Ape fossil known, and the oldest Caterrhine (the group that includes Old World Monkeys and Great Apes) that can be placed in any modern group, Sivapithecus indicus from the Miocene Chinji Formation of Pakistan, which has been identified as a member of the Ponginae (the group that includes modern Orangutans), and Sahelanthropus tchadensis from the Late Miocene Nawata Formation of Toros Menalla in northern Chad, thought to be an Hominin (the group that includes modern Humans) that lived shortly after the split with the Chimpanzees. No fossil Gibbons were included in the study, as the relationships of the few fossil Gibbons known to modern Gibbons are far from clear. This study suggests that Hoolock tianxing split from its closest related species (Hoolok leuconedys) about 1.14 million years ago, in the Middle Pleistocene.

A juvenile male of Hoolock tianxing from Mt. Gaoligong jumping across trees. Lei Dong in Fan et al. (2016).

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Landslide kills 78-year-old man on Cebu Island, The Philippines.

A landslide has killed a 78-year-old man in the village of Kalunasan near the city of Cebu on Cebu Island on Saturday 14 January 2017. The incident happened at about 10.00 am local time, when the victim, identified as Calixto Taburnal, was attempting to clear away some debris in his garden left by an earlier event, apparently unaware that such small landslips can precede larger earth movements.

The approximate location of the 14 January 2017 Cebu Landslide. Google Maps.

The incident is reported to have happened following heavy rainfall 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. Cebu has a wet and dry tropical climate, with a long rainy season that lasts from May to January. The worst of the rains are usually over by January, making this sort of even rare at this time of the year, but like other areas of Southeast Asia the Philippines has suffered a longer and wetter rainy season than usual this year, leading to extreme weather related events later than would usually be expected.

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