Friday, 18 August 2017

Chilesaurus diegosuarezi: How an enigmatic Dinosaur sheds light on the evolution of the whole group.

Chilesaurus diegosuarezi is a Late Jurassic Dinosaur from the Toqui Formation of Chile first described in 2015. It shows an unusual combination of features, combining elements usually associated with Therapods, Protosauropods and Ornithischian Dinosaurs. At the time of its description it was considered that, on the balance of probability, it was a Tetanuran Theropod (the group that also includes Tyrannosaurids, Megalosaurids, Ornithomimids, Allosaurids, Maniraptorforms, and Birds), with a number of unTheropod-like features that derive from its adaptation to a herbivorous lifestyle, leading to convergent evolution of some features with the herbivorous Protosauropods and Ornithischians.

However, in a paper published in March this year (2017), a group of palaeontologists led by Matthew Baron of the Department of Earth Sciences at the University of Cambridge and the Department of Earth Sciences at the Natural History Museum, presented the results of a cladistic study of Dinosaur phylogenetics (computerised analysis of relationships within the group based entirely upon shared common features rather than assumed relationships), which appeared to overturn some long-held views on Dinosaur evolution, most notably that the Ornithischians had diverged from other Dinosaurs before the split between Theropods and Sauropods; Baron et al.'s analysis suggested that this was an inaccurate and antiquated view, based upon the value attributed to the structure of the hip joint by Victorian palaeontologists, and that in fact the Ornithischians were more closely related to the Theropods than the Sauropods, which were the first group to split away from other Dinosaurs, early in the history of the group.

In a new paper published in the journal Biology Letters on 15 August 2017, Mathew Baron and Paul Barrett, also of the Department of Earth Sciences at the Natural History Museum, re-investigate the phylogentic position of Chilesaurus diegosuarezi, with a view to using this enigmatic species to better understand the history of the whole group.

Using this methodology, Baron and Barrett conclude that Chilesaurus diegosuarezi is in fact an Ornithischian rather than a Tetanuran Theropod, although it is the closest known species to the base of this group, holding a sister-group relationship to the rest of the Ornithischia, which are all more closely related to one-another than to Chilesaurus diegosuarezi. This lends strong support to the theory that Theropods and Ornithischians are closely related, with the 'primitive' Chilesaurus diegosuarezi being an Ornithischian that retains a number of Theropod-like features,

 Simplified time-calibrated strict consensus tree in which Chilesaurus is recovered within Ornithischia. Silhouettes represent supraspecific taxa—from left to right: Sauropodomorpha, Heterodontosauridae, Genasauria and Neotheropoda. Baron & Barrett (2017).

Chilesaurus diegosuarezi lacks a number of features usually thought of as being diagnostic of Ornithischian Dinosaurs, such as the predentary bone at the anterior end of the lower jaw, which presumably precluded its inclusion in the Ornithischia in its original description. However under the new classification proposed by Baron and Barrett this is not a problem, as these features are presumed to have evolved after the ancestors of  Chilesaurus diegosuarezi split away from the rest of the group.

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Over 100 feared dead after landslide in Ituri Province, Democratic Republic of Congo.

Over a hundred people are feared to have died after a landslide swept through the village of Tora on the shores of Lake Albert in Ituri Province in the northeast of the Democratic Republic of Congo on Wednesday 16 August 2017. The event happened after several days of heavy rain in the area, when a section of hillside collapsed onto the village. Landslides are a common problem after severe weather, 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.

The approximate location of the 16 August 2017 Tora landslide. Google Maps.

Ituri Province lies slightly to the north of the Equator, and has a climate that is wet for most of the year, though August is the rainiest month, typically receiving about 400 mm of precipitation. Landslides are common in the area, due to a combination of high rainfall, soil with a high content of volcanic ash (which tends to make it more friable) and frequent seismic activity, with the situation made worse by unregulated mining and deforestation, both of which tend to destabilise hillslopes.

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Thursday, 17 August 2017

Flooding in Bihar State, India, kills at least 98.

At least 98 people have died and over seven million have been forced to flee their homes in flooding across the state of Bihar in India this week. Twenty people are known to have died in Araria District, fourteen in East Champaran, thirteen in West Champaran, twelve in Madhepura, eleven in Sitamarhi, eight in Kisanganj, five each in Purnea and Madhubani, four in Darbhanga, three in Saharsa, two in Sheohar and one in Supual. The flooding has left many more without access to food and clean water, and washed away many roads and railways, leading the Indian National Disaster Response Force to drop supplies by air in areas where local populations cannot be reached in any other way.

People affected by flooding in Bihar State, India, this week. Times Now.

The flooding has been triggered by heavy rainfall in Nepal, associated with the Asian Summer Monsoon, which has caused the Koshi, Mahananda, Gandak, Bagmati and Ganga rivers to swell and breach their banks in many places, and made worse by high rainfall across Bihar itself.

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. This situation is particularly intense in South Asia, due to the presence of the Himalayas. High mountain ranges tend to force winds hitting them upwards, which amplifies the South Asian Summer Monsoon, with higher winds leading to more upward air movement, thus drawing in further air from the sea. 

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

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Wednesday, 16 August 2017

Homes evacuated after sinkhole opens up in Wednesbury, England.

Several homes have been evacuated after a sinkhole opened up in the drive of a house in the Black Country town of Wednesbury, on Saturday13 August 2017.  The hole is about 3 m wide and 3.65 m deep, and has caused a wall to collapse and partially trapped a car that was parked on a neighbouring drive.

Parked car partially trapped by a sinkhole outside a house in Wednesbury, England. ITV News Central.

Sinkholes are typically caused by the erosion of soft sediments or limestone beneath the surface, creating voids that can open up unexpectedly. On this occasion the hole appears to have been triggered by the collapse of a sewer main, which lead to the washing away sediments beneath the road, and triggering the collapse of a water main, leading to further water loss and further erosion, eventually causing the overlying road to collapse.

The approximate location of the August 2017 Wednesbury sinkhole. Google Maps. 

The origin of this particular sinkhole is yet to be determined. It is likely to be related to old coal mineworkings in the area, which was the site of extensive coal mining from the mode nineteenth century onwards, with not all former mines properly recorded, and such mines are prone to collapses, particularly after periods of wet weather. However Wednesbury is also situated on soft limestone, which is eroded over time by acid in rainwater (most rainwater is slightly acidic, though pollution can make this worse), and can collapse suddenly, causing overlying sediments to collapse into the hole and a sinkhole to open up. This can be triggered by human activity, such as pumping water out (which causes the water to flow, facilitating acid dissolution of the limestone), but is essentially a natural process.

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Magnitude 4.7 Earthquake in Batna Province, Algeria.

The United States Geological Survey recorded a Magnitude 4.7 Earthquake at a depth of 10 km, about 11 km to the northwest of the city of Merouana in Batna Province, Algeria, at about 3.50 pm local time (about 2.50 pm GMT) on Tuesday 15 August 2017. There are no reports of any damage or injuries associated with this event, though people have reported feeling it in Merouana and N'gaous.

The approximate location of the 15 August 2017 Merouana Earthquake. USGS.

Algeria lies on the northernmost part of the African Plate, while southern Europe to the north is part of Eurasia. Africa is pushing into Europe from the south, which causes Earthquakes around the Mediterranean Basin. These are most common in southeast Europe, but those in northwest Africa, while less frequent, are often larger and more deadly.

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Total Solar Eclipse to be visible from United States, 21 August 2017.

A total eclipse of the Sun will be visible from parts of the United States on Monday 21 August 2017, with a partial eclipse visible from the rest of North and Central America, as well as the Islands of the Caribbean, Colombia, Ecuador, Venezuela, Guyana, Suriname, French Guiana, Iceland, Ireland, Scotland, southern Scandinavia and parts of Brazil, Peru and Bolivia and (briefly) England, western Iberia, parts of West Africa and northwest Brazil. 

The path of the 21 August 2017 Solar Eclipse. The total eclipse will be visible along the central dark grey path. A partial eclipse will be visible from the shaded areas; in the lighters area the full eclipse will not be visible as it will have started before dawn (west) or will continue after sunset (east). The red lines are the Equator and the Greenwich Meridian. HM Nautical Almanac Office.

Eclipses are a product of the way the Earth, Moon and Sun move about one-another. The Moon orbits the Earth every 28 days, while the Earth orbits the Sun every 365 days, and because the two Sun and Moon appear roughly the same size when seen from Earth, it is quite possible for the Moon to block out the light of the Sun. At first sight this would seem likely to happen every month at the New Moon, when the Moon is on the same side of the Earth as the Sun, and therefore invisible (the Moon produced no light of its own, when we see the Moon we are seeing reflected sunlight, but this can only happen when we can see parts of the Moon illuminated by the Sun). 

The relative positions of the Sun, Moon and Earth during a Solar eclipse. Starry Night.

However the Moon does not orbit in quite the same plane as the Earth orbits the Sun, so the Eclipses only occur when the two orbital planes cross one-another; this typically happens two or three times a year, and always at the New Moon. During Total Eclipses the Moon entirely blocks the light of the Sun, however most Eclipses are Partial, the Moon only partially blocks the light of the Sun.

How the differing inclinations of the Earth and Moon's orbits prevent us having an eclipse every 28 days. Starry Skies.

Although the light of the Sun is reduced during an Eclipse, it is still extremely dangerous to look directly at the Sun, and viewing eclipses should not be undertaken without appropriate equipment.

 Animation showing the shadow of the Moon at five minute intervals on Friday 20 March 2015. Andrew Sinclair/HM Nautical Almanac.

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Monday, 14 August 2017

Asteroid 2017 PK25 passes the Earth.

Asteroid 2017 PK25 passed by the Earth at a distance of  853 900 km (2.22 times the average distance between the Earth and the Moon, or 0.57% of the average distance between the Earth and the Sun), slightly before 2.10 am GMT on Monday 14 August 2017. There was no danger of the asteroid hitting us, though had it done so it would have presented no threat. 2017 PK25 has an estimated equivalent diameter of 16-52 m (i.e. it is estimated that a spherical object with the same volume would be 16-52 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 26 and 9 km above the ground, with only fragmentary material reaching the Earth's surface.

The calculated orbit of 2017 PK25 Minor Planet Center.

2017 PK25 was discovered on 12 August 2017 (two days before its closest approach to the Earth) by the Atlas MLO Telescope at Mauna Loa Observatory in Hawaii. The designation 2017 PK25 implies that the asteroid was the 635th object (object K25) discovered in the first half of August 2017 (period 2017 P). 

2017 PK25 has a 268 day orbital period, with an elliptical orbit tilted at an angle of 25.9° to the plain of the Solar System which takes in to 0.46 AU from the Sun (46% of the distance at which the Earth orbits the Sun; slightly outside the orbit of the planet Mercury) and out to 1.17 AU (17% further away from the Sun than the Earth). This means that close encounters between the asteroid and Earth are fairly common, with the last thought to have happened in February this year and the next predicted in August 2020. Although it does cross the Earth's orbit and is briefly further from the Sun on each cycle, 2017 NS1 spends most of its time closer to the Sun than we are, and is therefore classified as an Aten Group Asteroid.

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