Saturday, 25 March 2017

Eruption on Mount Kambalny, Kamchatka, for the first time in over 250 years.

The Kamtchatka Volcanic Eruption Response Team has issued a warning to aviation following an eruption on Mount Kambalny on the southern Kamchatka Peninsula on Friday 24 March 2017. The stratovolcano (cone-shaped volcano made up of successive layers of ash and lava) erupted suddenly for the first time since 1769, producing an ash column 7-8 km high that drifted around 255 km to the southwest. The eruption is not thought to present any immediate threat to Human life due to the remote location of the volcano. The area is occasionally visited by parties of tourists, but none are thought to have been in the vicinity at the time of the eruption.

MODIS/TERRA satellite image of ash from Mount Kambalny (dark grey) drifting to the southwest of the volcano. Kamchatka Volcanic Eruption Response Team.

Mount Kambalny is the southernmost active volcano on the Kamchata Peninsula, and rises 2156 m above sea level (1970 m above the surrounding plain). The volcano probably began erupting in the early Holocene (i.e. slightly less than 10 000 years ago), with much of the current structure formed in a series of large eruptions and collapses about 6300 years ago. The last major eruption on the volcano probably took place about 600 years ago, with all activity halting in the 1760s, though fumerole activity (emissions of volcanic gas) is frequently recorded on the related Pauzhetka volcanic field, a tectonic depression to the north of Mount Kambalny, thought to be a volcanic caldera and containing the 14 by 10 km Kurile Lake.

The Kamchatka Peninsula lies on the eastern edge of the Okhotsk Plate, close to its margin with the Pacific and North American Plates. The Pacific Plate is being subducted along the margin, and as it does so it passes under the southern part of the Kamchatka Peninsula, and as it does so is partially melted by the friction and the heat of the Earth's interior. Some of the melted material then rises through the overlying Okhotsk Plate as magma and fuelling the volcanoes of southern Kamchatka.

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Dinosaur phylogenetics, a radical new proposal.

Phylogenetics is the study of the relationships between organisms, as determined by examining similarities between species and reconstructing family trees. The early origins of the science relied very much on informed guesswork, but modern phylogenetics is a highly mathematical discipline, in which practitioners attempt to measure mathematically differences between the morphologies, or better still DNA, of different species, and allow computer models to estimate the most likely relationships between them. The phylogeny of the Dinosaurs, although it has changed a great deal in detail with the discovery of numerous new species, has remained essentially the same since 1887, with the earliest Dinosaurs appearing in the Middle-to-Late Triassic and rapidly diverging into two distinct groups the ‘Lizard-hipped’ Saurischians and the ‘Bird-hipped’ Ornithischians, and the Saurischians splitting shortly afterwards into the Sauropods and Theropods.

In a paper published in the journal Nature on 23 March 2017, Matthew Baron of the Department of Earth Sciences at the University of Cambridge and the Department of Earth Sciences at the Natural History Museum, David Norman also of the Department of Earth Sciences at the University of Cambridge and Paul Barrett also of the Department of Earth Sciences at the Natural History Museum describe a radically different phylogeny for the Dinosaurs, based upon a new study which incorporated data on 457 morphological characteristics of 74 taxa of Dinosaurs and Dinosauromorph Archosaurs (i.e. Archosaurs thought to be closely related to Dinosaurs). 

Remarkably Baron et al. did not recover the two ‘Saurischian’ Dinosaur groups as being one-another’s closest relatives to the exclusion of the Ornithischians; rather they produced a model in which the Dinosaurs split early into two groups, one comprising the Sauropods plus the Herrerasauridae (a group of early Dinosaurs generally thought to be primitive Theropods) and the other comprising the Ornithischians plus all other Theropods.

Phylogenetic relationships of early dinosaurs. Time-calibrated strict consensus of 94 trees from an analysis with 73 taxa and 457 characters. (A) the least inclusive clade that includes Passer domesticus, Triceratops horridus and Diplodocus carnegii — Dinosauria, as newly defined. (B) the least inclusive clade that includes Passer domesticus and Triceratops horridus — Ornithoscelida, as defined. (C) the most inclusive clade that contains Diplodocus carnegii, but not Triceratops horridus —Saurischia, as newly defined. All subdivisions of the time periods (white and grey bands) are scaled according to their relative lengths with the exception of the Olenekian (Early Triassic), which has been expanded relative to the other subdivisions to better show the resolution within Silesauridae and among other non-Dinosaurian Dinosauromorphs. Baron et al. (2017).

If this is correct, then it presents a number of serious challenges for our understanding of Dinosaur phylogeny. Firstly there is the definition of the term 'Dinosaur' itself. The current definition of Dinosaur is 'Passer domesticus, Triceratops horridus, their most recent common ancestor and everything descended from it'. This made sense because Passer domesticus, the modern House Sparrow, is a highly derived Theropod and Triceratops horridus, is a highly derived Ornithischian, so that a clade comprising all the descendants of their most recent common ancestor and everything descended from it, would, if Theropods and Ornithischians are the most distantly related Dinosaur groups, include everything we would consider to be a Dinosaur. However, if Ornithischians and Theropods are more closely related to one-another than either group is related to the Sauropods, then Sauropods can no longer be considered to be Dinosaurs. Since this goes completely against the common understanding of the term Dinosaur, Baron et al. suggest that rather than exclude the Sauropods from the Dinosaurs, the definition of the group should be amended to 'Passer domesticus, Triceratops horridus and Diplodocus carnegii, their most recent common ancestor and everything descended from it', thereby retaining everything that we would think of as being a Dinosaur within the group.

Then there is the problem of how to split the Dinosaurs into subgroups. The taxon Saurischia, which comprises the Theropods plus the Suaropods, and which has for over a hundred years been seen as one of the major Dinosaur divisions, is no longer valid under this hypothesis. Baron et al. suggest that instead the term Ornithoscelida, first proposed by Thomas Huxley in 1870 to describe a group comprising the Compsognatha (Theropods), Iguanodontidae (Ornithischians), Megalosauridae (Theropods) and Scelidosauridae (Ornithischians), i.e. a group of Dinosaur clades thought to be unrelated since the Ornithischian/Saurischian split was proposed in 1887, but which now appears valid. They retain the term Saurischia to describe the clade that includes the Sauropods and Herreosaurs, as these groups were both fall within the original definition of that group.
This hypothesis also has implications for the origins of the Dinosaurs, and the nature of the earliest members of the group. Since the earliest Therapods (the Herrerasauridae) and the earliest Ornithischians (the Heterodontosaurids) were both thought to have been carnivores, and the earliest members of the most closely related non-Dinosaurian group, the Silesauridae, were also thought to have been carnivores, it was presumed that the earliest Dinosaurs were probably carnovores, but it was unclear what they would have been like. However if the Herrerasauridae are outside the Theropods, then this balance changes. The earliest member of the Theropods become Eoraptor, a small omnivorous Dinosaur with heterodont dentition (i.e. different shaped teeth in different parts of the mouth) and grasping hands, while the earliest Ornithischians, the Heterodontosaurids, were also small with heterodont dentition and grasping hands, as were the Prosuaropods (earliest Suaropods). Only the Herrerosaurs differe from this pattern, being small with grasping hands but having serrated, recurved teeth reminiscent of later Theropods and indicatinve of a hypercarnivorous diet (diet in which little or no vegetable food is ingested), however, this group is not well known, and it is possible that early member of the group did have a different form of dentition. This points to a model where the earliest Dinosaur would have been a small, omnivorous animal with grasping hands and heterodont dentition, a versatile generalist lifestyle and anatomy that could explain how the Dinosaurs were able to diversify rapidly into so many different niches.

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Friday, 24 March 2017

London school closed by sinkholes linked to disused mine workings.

A school in northwest London has been forced to close after a series of sinkholes that opened up in its grounds were found to be linked to disused mineworkings running beneath the site. The first hole appeared in a car park at Pinner Wood School in Harrow appeared in the summer of 2015, prompting Harrow Council to commission an investigation into the site by geotechnical consultants Peter Brett Associates. This survey used laser survey borehole equipment to determine the structure of the ground beneath the school and discovered a series of tunnels, believed to be abandoned early nineteenth century mineworkings, running through a chalk layer 20 m below the surface. These tunnels appear to be beginning to collapse, raising concerns about the safety of structures above them, which has caused Harrow Council to close the school indefinitely while attempts are made to remedy the situation. Lessons will be held at other education facilities in the borough for the time being; it is not yet certain when (or if) it will be possible for the school to reopen.

Digital model of the tunnels below Pinner Wood School. Harow Council.

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.

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Thursday, 23 March 2017

Asteroid 2017 FD3 passes the Earth.

Asteroid 2017 FD3 passed by the Earth at a distance of 180 000 km (0.47 times the average distance between the Earth and the Moon, 0.12% of the average distance between the Earth and the Sun), slightly before 2.30 pm GMT on Friday 17 March 2017. There was no danger of the asteroid hitting us, though had it done so it would have presented no threat. 2017 FD3 has an estimated equivalent diameter of 5-17 m (i.e. it is estimated that a spherical object with the same volume would be 5-17 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 40 and 25 km above the ground, with only fragmentary material reaching the Earth's surface.

The calculated orbit of 2017 FD3. Minor Planet Center.

2017 FD3 was discovered on 19 March 2017 (two days after its closest encounter with the Earth) by the University of Arizona's Catalina Sky Survey, which is located in the Catalina Mountains north of Tucson. The designation 2017 FD3 implies that it was the 79th asteroid (asteroid D3) discovered in the second half of March 2017 (period 2017 F).
2017 FD3 is calculated to have a 1008 day orbital period and an elliptical orbit tilted at an angle of 2.12° to the plain of the Solar System that takes it from 0.87 AU from the Sun (i.e. 87% of the average distance at which the Earth orbits the Sun) to 3.05 AU from the Sun (i.e. 305% of the average distance at which the Earth orbits the Sun, 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 are extremely common, with the last having occurred in November 1969 and the next predicted in November 2019. 2017 FD3  also has frequent close encounters with the planet Mars, with the next predicted for April 2080.
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Wednesday, 22 March 2017

Magnitude 5.5 Earthquake beneath southern Bali.

The United States Geological Survey recorded a Magnitude 5.5 Earthquake at a depth of 118.5 km about 2 km to the northwest of Banjar Pasekan on Bali in Indonesia at about 7.10 am on Wednesday 22 March 2017 local time (about 11.10 pm on Tuesday 21 March GMT) . The event was felt across most of Bali, Lombok and East Java, but there are no reports of any damage or injuries.

The approximate location of the 22 March 2017 Bali Earthquake. USGS.

The Indo-Australian Plate, which underlies the Indian Ocean to the south of Java, Bali and Lombok, is being subducted beneath the Sunda Plate, a breakaway part of the Eurasian Plate which underlies the islands and neighbouring Sumatra, along the Sunda Trench, passing under the islands, 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 Java and neighbouring islands. 

Subduction along the Sunda Trench beneath Java, Bali and Lombok. Earth Observatory of Singapore.

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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