Friday 31 July 2015

Asteroid 2015 OQ21 passes the Earth.

Asteroid 2015 OQ21 passed by the Earth at a distance of 567 900 km (1.48 times the average distance between the Earth and the Moon, or 0.38% of the average distance between the Earth and the Sun), at about midnight GMT between Thursday 23 and Friday 24 July 2015. There was no danger of the asteroid hitting us, though had it done so it would have presented only a minor threat. 2015 OQ21 has an estimated equivalent diameter of 4-16 m (i.e. it is estimated that a spherical object with the same volume would be 4-16  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 43 and 25 km above the ground, with only fragmentary material reaching the Earth's surface.

The calculated orbit of 2015 OQ21. JPL Small Body Database.

2015 OQ21 was discovered on 19 July 2015 (four days before its closest approach to the Earth) by the University of Hawaii's PANSTARRS telescope on Mount Haleakala on Maui. The designation 2015 OC21 implies that it was the 528th asteroid (asteroid C21) discovered in the second half of July  2015 (period 2015 O).

2015 OQ21 has a 254 day orbital period, with an elliptical orbit tilted at an angle of 1.33° to the plain of the Solar System which takes in to 0.50 AU from the Sun (50% of the distance at which the Earth orbits the Sun, considerably inside the orbit of Venus) and out to 1.07 AU (7% 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 April this year and the next predicted in May 2017. Although it does cross the Earth's orbit and is briefly further from the Sun on each cycle, 2015 OQ21 spends most of its time closer to the Sun than we are, and is therefore classified as an Aten Group Asteroid. This also means that close encounters between 2015 OQ21 and Venus are quite common, with the last having occurred in February 2010 and the next predicted for August 2016.

See also...

Asteroid (242191) 2003 NZ6 passed by the Earth at a distance of 12 470 000 km (32.4 times the average distance between the Earth and the Moon, or 8.33% of the average distance between the Earth and the...


Asteroid (385186) 1994 AW1 passed by the Earth at a distance of 9 725 000 km (25.3 times the average distance between the Earth and the Moon, or 6.50% of the average distance between the Earth and the...


Asteroid 2011 YC29 passed by the Earth at a distance of 9 438 000 km (24.5 times the average distance between the Earth and the Moon, or 6.31% of the average distance between the Earth and the Sun), at about 10.10 am GMT on Wednesday 15 July...



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Magnitude 1.3 Earthquake near Glencoe, Scotland.

The British Geological Survey recorded a Magnitude 1.3 Earthquake at a depth of about 10 km about 5 km to the west of Glencoe in the district of Lochaber in Highland, Scotland, slightly after 9.25 pm British Summertime (slightly after 10.35 pm GMT) on Thursday 20 July 2015. This was not a major event, and presented no threat to human life or property, but was felt in the village of Ballachulish.

The approximate location of the 20 July 2015 Lochaber Earthquake. Google Maps.

Earthquakes become more common as you travel north and west in Great Britain, with the west coast of Scotland being the most quake-prone part of the island and the northwest of Wales being more prone  to quakes than the rest of Wales or most of England. 

The precise cause of Earthquakes in the UK can be hard to determine; the country is not close to any obvious single cause of such activity such as a plate margin, but is subject to tectonic pressures from several different sources, with most quakes probably being the result of the interplay between these forces.

Britain is being pushed to the east by the expansion of the Atlantic Ocean and to the north by the impact of Africa into Europe from the south. It is also affected by lesser areas of tectonic spreading beneath the North Sea, Rhine Valley and Bay of Biscay. Finally the country is subject to glacial rebound; until about 10 000 years ago much of the north of the country was covered by a thick layer of glacial ice (this is believed to have been thickest on the west coast of Scotland), pushing the rocks of the British lithosphere down into the underlying mantle. This ice is now gone, and the rocks are springing (slowly) back into their original position, causing the occasional Earthquake in the process. 

(Top) Simplified diagram showing principle of glacial rebound. Wikipedia. (Bottom) Map showing the rate of glacial rebound in various parts of the UK. Note that some parts of England and Wales show negative values, these areas are being pushed down slightly by uplift in Scotland, as the entire landmass is quite rigid and acts a bit like a see-saw. Climate North East.

Witness accounts of Earthquakes can help geologists to understand these events, and the structures that cause them. If you felt this quake, or were in the area but did not (which is also useful information) then you can report it to the British Geological Survey here.

See also...

The British Geological Survey recorded a Magnitude 1.4 Earthquake at a depth of about 2 km off the south coast of the Isle of Mull, in Argyll and Bute, Scotland...


The British Geological Survey recorded a Magnitude 1.3 Earthquake at a depth of about 3 kmto the west of Loch Rannoch in Perth and Kinross, Scotland, slightly...


The British Geological Survey recorded a Magnitude 2.2 Earthquake at a depth of about 11 km to the south of Loch Shiel in...

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Thursday 30 July 2015

Babibasiliscus alxi: A Casquehead Lizard from the Early Eocene of Wyoming.


Casquehead Lizards, Corytophanidae, are a group of Iguanid Lizards found from the tropical forests of southern Mexico, through Central America to the northwest of South America. They belong to a group of Iguanians, the Pleurodonta, found today almost exclusively in the Americas, with non-American members of the group known only from the islands of Madagascar and Fiji, and studies of the group taking into account relationships between modern species and their biogeographical distribution suggest that they probably originated in the American tropics. However a single fossil specimen of a Casquehead Lizard is known from the Early Eocene of Central Europe, suggesting that their ancient distribution might have been somewhat different from that seen today.

In a paper published in the journal PLoS One on 1 July 2015, Jack Conrad of the Department of Anatomy at the New York Institute of Technology College of Osteopathic Medicine and the Department of Vertebrate Paleontology at the American Museum of Natural History describes a new species of Casquehead Lizard from the late Early Eocene Bridger Formation of Uinta County in Wyoming (about 48 million years old).

The new species is named Babibasiliscus alxi, where ‘Babi-’ means ‘older male cousin’ in the language of the Shoshone people who inhabited the region where the fossil was discovered, and ‘-basiliscus’ (Basiliscus) is the name of a modern genus of Casquehead Lizards, while ‘alxi’ honours John Alexander, who discovered the specimen from which the species was described. The single known specimen comprises a nearly complete skull with articulated jaws plus the first two vertebrae, undistorted or compacted, but with the premaxilla, posterior half of the frontal, parietal, postfrontals, postorbitals, squamosals, supratemporals, supraoccipital, dorsal half of each quadrate, and the anterior tips of both dentaries lost to erosion.

Babibasiliscus alxi: Photographs in (A) right lateral, (B) dorsal, and (C) ventral views. Digital reconstructions derived from High Resolution X-ray Computerised Tomography in (D) left lateral view and (E) transverse section. The vertical red line in (D) indicates the plane of section in (E). Conrad (2015).

A phylogenetic analysis of Casquehead Lizards including Babibasiliscus alxi places it firmly within the modern group, closely related to the living genus Laemanctus. Wyoming is considerably outside the range of modern Casquehead Lizards, with a strongly seasonal climate, typically including heavy winter snowfall. However during the Eocene global climates are known to have been considerably warmer than today, and both Babibasiliscus alxi from Wyoming and Geiseltaliellus maarius from the Eocene of Central Europe are interpreted as having lived in tropical forests not dissimilar from those inhabited by modern Casquehead Lizards.

Phylogeny of Corytophanids and distribution of the group. (A) Time-calibrated phylogeny of the Corytophanid genera with representative illustrations of their skull morphologies. Conrad (2015).

Modern Iguanians are divided into two groups, the Chamaeleontiformes, comprising the Chameleons, Agamas, and their relatives, which are found in the Old World, and the Pleurodonta, comprising the Iguanas, Basilisks, Anoles, Fence Lizards, and their relatives, which are found in the Americas (with the exception of the Opluridae which are found in Madagascar and the genus Brachylophus from Fiji). However the earliest Iguanians are found in Cretaceous deposits dating to before the separation of North America and Eurasia, with the majority of species found in Asia, suggesting this is where the group originated. By the Eocene Iguanians were divided into the modern groups Chamaeleontiformes and Pleurodonta, though with specimens from both groups found on both sides of the Atlantic, and in particular many species of Pleurodonts found in the Old World. It is therefore thought that the modern distribution of the groups reflects a relict distribution shaped by post-Eocene cooling rather than the modern groups having derived from isolated populations after the separation of the continents. Conrad suggests that this interpretation can also be applied to the modern Casquehead Lizards, with the group distributed across tropical forests in what is now the Northern Hemisphere temperate zone during the Eocene (when they were probably excluded from the far hotter tropics), and subsequently having withdrawn to the Neotropics during later Cainozoic cooling.

See also…

Anles are small Iguanid Lizards found in the Southern United States, Mexico, Central America and the Caribbean. Twig Anoles, Norops spp., form a distinct cluster of medium sized Anole Lizard species within the genus Norops. There are currently eight...


Treerunners of the genus Plica are Iguanid Lizards found in South America east of the Andes. They are medium sized, conspicuous Lizards that are active...


Western Europe is thought to have had a diverse Squamate (Snake and Lizard) fauna during the Miocene, but to have largely lost this during the cooling climate of the Plio-Pleistocene, during which...


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Saturday 25 July 2015

Zhenyuanlong suni: A large feathered Dromaeosaur from the Jehol Biota.


Dromaeosaurid Dinosaurs are among the closest non-Avian relatives of the Birds and show many similarities to the earliest members of that group, making understanding Dromaeosaurs important for understanding the origin of Birds. In particular many Dromaeosaur specimens from the Early Cretaceous of Liaoning Province, China, have been shown to possess extremely Bird-like feather coats, and in several cases feathered wings which may have allowed them to fly. This is particularly interesting as the Liaoning specimens are not thought to represent a tight monophyletic group (i.e. a group of species more closely related to one-another than anything else), but rather a diverse group of Dromaeosaurs with exceptional preservation, part of the Jehol Biota of exceptionally well preserved Early Cretaceous fossils, suggesting that feathers were also present in Dromaeosaurs from other locations even if they have not been preserved. The smallest and most numerous Liaoning Dromaeosaurs are placed in the genus Microraptor and may (or may not) represent several species of small (cat-sized) Dinosaurs fully capable of flight, while the largest, Tianyuraptor, is a much larger animal with reduced fore-limbs highly unlikely to have been capable of supporting it in flight. Unfortunately Tianyuraptor is known only from a single specimen lacking feathers; it is impossible to determine whether this species was truly featherless from a single specimen, nor to speculate about what sort of feathers it may have possessed.

In a paper published in the journal Nature Scientific Reports on 16 July 2015, Junchang Lü of the Institute of Geology of the Chinese Academy of Geological Sciences and the Key Laboratory of Stratigraphy and Paleontology of the Ministry of Land and Resources of China and Stephen Brusatte of the School of GeoSciences at the University of Edinburgh, describe a new species of Dromaeosaur from the Yixian Formation of Jianchang County in Liaoning Province.

The new species is named Zhenyuanlong suni, honouring Zhenyuan Sun who discovered the specimen; the suffix ‘-long’ means ‘Dragon’ in Chinese, making ‘Zhenyuanlong suni’ ‘Zhenyuan Sun’s Dragon’. The specimen comprises an almost complete specimen preserved on in two dimensions on three separate blocks, with only the end part of the tail missing. The specimen is 126.6 cm in length, but it is thought to have been about 165 cm long in life. Not all of the vertebrae fused in adult Dinosaurs are fully fused in this specimen, leading Lü and Brusatte to conclude it was a subadult at the time when it died.

The holotype of the large-bodied Liaoning Dromaeosaurid Zhenyuanlong suni. Lü & Brusatte (2015).

Like Tianyuraptor, Zhenyuanlong suni has relatively small forelimbs for the size of its body, however unlike Tianyuraptor an extensive feather coating is preserved on all of Zhenyuanlong suni except its hindlimbs (these are preserved on a separate block which does not contain any feathers, making it hard to assess whether feathers were originally present on the hindlimbs; feathered hindlimbs are common in both smaller Dromaeosaurs and early Birds). Notably these show layered feathers similar to those seen in modern Birds and Microraptor.

The integument of the large-bodied, short-armed Liaoning Dromaeosaurid Zhenyuanlong suni. (A) Overview of the skeleton with regions of integument indicated with grey highlight; (B) proximal tail; (C) left forearm; (D) right forearm; (E) closeup of coverts on right forearm. Lü & Brusatte (2015).

Without a full biomechanical analysis (which has not been carried out for Zhenyuanlong suni at the time of writing) it is impossible to say whether or not it was capable of flying or gliding, but the combination of a large body size and small forelimbs makes this seem somewhat unlikely, leading to support for the alternative theory that feathered wings were first developed for some other purpose in Bird-like Dinosaurs and later co-opted for flight in Birds and possibly some small Dromaeosaurs. This is not uncommon as evolution does not plan ahead, and major biological revolutions often come about when organs or metabolic pathways adapted to one purpose are then used for another.

See also…

The Dromaeosaurid (a type of small Theropod Dinosaur closely related to Birds and Troodontids) Saurornitholestes langstoni was first...


In December 2000 Xing Xu, Zonghe Zhou and Xioalin Wang of the Institute of Vertebrate Paleontologyand Paleoanthropology of the Chinese Academy of...


Dromaeosaurs were small Therapod Dinosaurs, thought to have been the group most closely related to...

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Thursday 23 July 2015

Asteroid (242191) 2003 NZ6 passes the Earth.

Asteroid (242191) 2003 NZ6 passed by the Earth at a distance of 12 470 000 km (32.4 times the average distance between the Earth and the Moon, or 8.33% of the average distance between the Earth and the Sun), at about 5.55 pm GMT on Saturday 18 July 2015. There was no danger of the asteroid hitting us, though had it done so it would have presented a considerable threat. (242191) 2003 NZ6 has an estimated equivalent diameter of 300-940 m (i.e. it is estimated that a spherical object with the same volume would be 300-940  m in diameter), and an object of this size would pass through the atmosphere and directly impact the ground with a force of about 1110-1 45 000 megatons (roughly 65 300 to 2 650 000 times the explosive energy of the Hiroshima bomb), causing devastation over a wide area and creating a crater about 4.5-13 kilometers across, and resulting in global climatic problems that could last for decades or even centuries.

The calculated orbit of (242191) 2003 NZ6. JPL Small Body Database.

(242191) 2003 NZ6 was discovered on 9 July 2003 by the Massachusetts Institute of Technology's Lincoln Near Earth Asteroid Research Laboratory in Socorro, New Mexico. The designation 2003 NZ6 implies that it was the 175th asteroid (asteroid Z6) discovered in the first half of July 2003 (period 2003 Z), while the designation 242191 implies that it was 242 191st asteroid ever discovered (asteroids are not given this longer designation immediately to avoid naming double or false sightings).

(242191) 2003 NZ6 has a 258 day orbital period, with an elliptical orbit tilted at an angle of 18.2° to the plain of the Solar System which takes in to 0.43 AU from the Sun (43% of the distance at which the Earth orbits the Sun, slightly outside the orbit of Mecury) and out to 1.18 AU (18% 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 May 2012 and the next predicted in April 2017. Although it does cross the Earth's orbit and is briefly further from the Sun on each cycle, (242191) 2003 NZ6 spends most of its time closer to the Sun than we are, and is therefore classified as an Aten Group Asteroid. This also means that close encounters between (242191) 2003 NZ6 and Venus are also quite common, with the last having occurred in April 2012 and the next predicted for August this year.

See also...

Asteroid (385186) 1994 AW1 passed by the Earth at a distance of 9 725 000 km (25.3 times the average distance between the Earth and the Moon, or 6.50% of the average distance between the Earth and the...


Asteroid 2011 YC29 passed by the Earth at a distance of 9 438 000 km (24.5 times the average distance between the Earth and the Moon, or 6.31% of the average distance between the Earth and the Sun), at about 10.10 am GMT on Wednesday 15 July...


Asteroid 2015 JH2 passed by the Earth at a distance of 11 830 000 km (30.8 times the average distance between the Earth and the Moon, or 7.91 % of the average distance between the Earth and the Sun), slightly before 2.40 am GMT on Thursday 9 July...



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Eruptions on Nevado del Ruiz.

The Instituto Colombiano de Geología y Minería (INGEOMINAS) reported an increase in seismic activity (earthquakes) beneath Nevado del Ruiz, a 5231 m stratovolcano (cone shaped volcano made up of layers of lava and ash) in the Los Nevados National Natural Park, at the northern end of the Ruiz-Tolima Volcanic Massif in Columbia on Monday 13 July 2015. Such Earthquakes are significant as they are often caused by magma moving in chambers beneath the volcano, and can be indicative of forthcoming eruptions. This was followed by a series of small ash eruptions which lead to ashfalls in villages up to 30 km from the volcano. This activity continued till Saturday 18 July, when the Washington Volcanic Ash Advisory Center reported a large eruption at about 5.30 am which produced an ash column rising 6.1 km above the mountain. A second smaller eruption was reported on 19 July, this time producing an ash column about 1 km in height.

Ash column over Nevado del Ruiz on 19 July 2015. Volcano Discovery.

The Ruiz-Tolima Volcanic Massif runs north-to-south parallel to the Parallel to the Pacific Coast of Columbia. It is fed by the subduction of the Nazca Plate beneath the South American Plate along the Peru-Chile Tench, which runs approximately parallel to the entire western coast of South America. As the Nazca Plate it sinks into the Earth's interior it is heated by the planet's interior heat. This melts minerals within the subducting plate, some of which then rise through the overlying South American Plate as magma, fueling volcanoes in the Andes along the full extent of the South American west coast.

The approximate location of Nevado del RuizGoogle Maps.

See also...

Concern is rising in Colombia and Ecuador following a rise in seismic activity beneath Cerro Negro de Mayasquer, a volcano in the Andes straddling...


The United States Geological Survey recorded a Magnitude 5.0 Earthquake at a depth of 28.4 km in southern Tolima Department, Columbia, at about...


The Observatorio Vulcanológico and Sismológico de Popayán reported a sharp rise in seismic activity under Mount Sotará in southeast Columbia this month, with 110 Earth tremors of magnitudes between 0.2 and 1.6 at depths of 2-6 km, within 5 km of the summit between... 


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Monday 20 July 2015

Magnitude 1.6 Earthquake in Cumbria, England.

The British Geological Survey recorded a Magnitude 1.6 Earthquake at a depth of about 5 km about five kilometers to the south of the village of Caldbeck in Cumbria, England, slightly before 11.00 pm British Summertime (slightly before 10.00 pm GMT) on Friday 17 July 2015. There are no reports of any injuries associated with this event, though it may have been felt locally.

The approximate location of the 17 July 2015 Cumbria Earthquake. Google Maps.

Earthquakes become more common as you travel north and west in Great Britain, with the west coast of Scotland being the most quake-prone part of the island and the northwest of Wales being more prone  to quakes than the rest of Wales or most of England. However, while quakes in southern England are less frequent, they are often larger than events in the north, as tectonic presures tend to build up for longer periods of time between events, so that when they occur more pressure is released.

The precise cause of Earthquakes in the UK can be hard to determine; the country is not close to any obvious single cause of such activity such as a plate margin, but is subject to tectonic pressures from several different sources, with most quakes probably being the result of the interplay between these forces.

Britain is being pushed to the east by the expansion of the Atlantic Ocean and to the north by the impact of Africa into Europe from the south. It is also affected by lesser areas of tectonic spreading beneath the North Sea, Rhine Valley and Bay of Biscay. Finally the country is subject to glacial rebound; until about 10 000 years ago much of the north of the country was covered by a thick layer of glacial ice (this is believed to have been thickest on the west coast of Scotland), pushing the rocks of the British lithosphere down into the underlying mantle. This ice is now gone, and the rocks are springing (slowly) back into their original position, causing the occasional Earthquake in the process.

(Top) Simplified diagram showing principle of glacial rebound. Wikipedia. (Bottom) Map showing the rate of glacial rebound in various parts of the UK. Note that some parts of England and Wales show negative values, these areas are being pushed down slightly by uplift in Scotland, as the entire landmass is quite rigid and acts a bit like a see-saw. Climate North East.

Witness accounts of Earthquakes can help geologists to understand these events, and the structures that cause them. If you felt this quake, or were in the area but did not (which is also useful information) then you can report it to the British Geological Survey here.

See also...

The British Geological Survey recorded a Magnitude 1.7 Earthquake at a depth of 4 km in the Kents Bank area of Morcambe Bay, northwest England, at about 5.55...


The British Geological Survey recorded a Magnitude 1.9 Earthquake at a depth of 10 km about 7 km to the northwest of the town of Ulverston...


The British Geological Survey recorded a Magnitude 2.0 Earthquake at a depth of 12 km about 20 km to the southeast of the town of Kendle in Cumbria...


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