Thursday, 19 October 2017

Magnitude 4.8 Earthquake off the coast of Nicaragua.

The United States Geological Survey recorded a Magnitude  4.8 Earthquake at a depth of 76.5 km, about 25 km offshore of the Padre Ramos estuary on the coast of Chinandega Department, Nicaragua, slightly after 5.00 pm local time (slightly after 11.00 pm GMT) on Tuesday 17 October 2017. There are no reports of any damage or casualties associated with this event, though it was felt in Nicaragua and El Salvador.

 The approximate location of the 17 October 2017 Padre Ramos Earthquake. USGS.

Nicaragua is located on the southern part of the Caribbean Plate, close to its boundary with the Cocos Plate, which underlies part of the east Pacific. The Cocos Plate is being pushed northwards by expansion of the crust along the East Pacific Rise, and is subducted beneath the Caribbean Plate along the Middle American Trench, which runs parallel to the south coast of Central America, passing under the peninsula  as it sinks into the Earth's interior. This is not a smooth process, the plates tend to stick together, breaking apart again once the pressure from the northward movement of the Cocos Plate builds up to much, triggering Earthquakes. 

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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Heavy rains bring flooding to south and central Trinidad.

Central and southern parts of the Caribbean island of Trinidad have suffered widespread flooding after a period of heavy rains and thunderstorms that lasted about 24 hours across Wednesday 18 and Thursday 19 October 2017. There are no reports of any casualties associated with this flooding, but transport networks have been severely disrupted and many homes inundated.

Flooding on Trinidad on Wednesday 18 October 2017. Loop.

Like other parts of the Caribbean, Trinidad has suffered a series of flooding events this summer, associated with a series of particularly severe hurricanes. However this weeks flooding is not associated with any hurricane, but rather appears to have been caused by the movement of the Inter-Tropical Convergence System, a permanent low pressure system that circles the globe approximately on the equator. 

This system is caused by heat from the Sun, which is greater at the equator then elsewhere, causing air over the equator to rise, and drawing in air currents from the Northern and Southern Hemispheres, forming the trade winds. This updraughts pull up water vapour from the sea surface high into the atmosphere, where it eventually precipitates out of the cooler, less dense atmosphere, falling back as rain. 

Flooding on Trinidad on Wednesday 18 October 2017. Loop.

Importantly, while the actual equator is fixed, the tilt of the Earth relative to the Sun means that the point at which the Sun is directly overhead moves northward in the northern summer and south in the southern summer, creating a thermal equator, which the Inter-Tropical Convergence System follows, moving north in the north and south with the seasons (and since  the sea heats and cools more slowly than the land, this movement is more pronounced over land than sea). The upshot of this is a system of storms which circulates on the equator at the equinoxes, but which moves north and south to the tropics around the solstices. Furthermore this system moves further away from the equator in warmer years, and is predicted as being likely to do so more with global warming. It is this  Inter-Tropical Convergence System which has passed over Trinidad this week, causing storms and flooding over the island.

The approximate position of the Inter-Tropical Convergence System in July and January.
Mats Halldin/

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Wednesday, 18 October 2017

Asteroid 2017 RV1 passes the Earth.

Asteroid 2017 RV1 passed by the Earth at a distance of about 6 820 000 km (17.7 times the average distance between the Earth and the Moon, or 4.58% of the distance between the Earth and the Sun), slightly before 4.45 am GMT on Thursday 12 October 2017. There was no danger of the asteroid hitting us, though were it to do so it would have presented a significant threat. 2017 RV1 has an estimated equivalent diameter of 180-570 m (i.e. it is estimated that a spherical object with the same volume would be 180-570 m in diameter), and an object of this size would be predicted to be capable of passing through the Earth's atmosphere relatively intact, impacting the ground directly with an explosion that would be 12 000-600 000 times as powerful as the Hiroshima bomb. Such an impact would result in an impact crater over 2-8 km in diameter and devastation on a global scale, as well as climatic effects that would last decades or even centuries.

The calculated orbit of 2017 RV1. Minor Planet Center.

2017 RV1 was discovered on 12 September 2017 (thirty days before its closest approach to the Earth) by the University of Hawaii's PANSTARRS telescope on Mount Haleakala on Maui. The designation 2017 RV1 implies that it was the 46th asteroid (asteroid V1) discovered in the first half of September 2017 (period 2017 R).

2017 RV1 has a 1377 day orbital period and an eccentric orbit tilted at an angle of 2.04° to the plane of the Solar System, which takes it from 0.89 AU from the Sun (i.e. 89% of he average distance at which the Earth orbits the Sun) to 3.94 AU from the Sun (i.e. 394% 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 the asteroid has occasional close encounters with the planet Earth, with the last thought to have occurred in September 2002 next predicted to occur in September 2036. It is also calculated to have occasional close encounters with the planet Jupiter, with the last thought to have happened in October 1970 and the next predicted for February 2031. As an asteroid probably larger than 150 m in diameter that occasionally comes within 0.05 AU of the Earth, 2017 SN2 is also classified as a Potentially Hazardous Asteroid (it comes no closer to the Sun than 105% of the average distance at which the Earth orbit's the Sun, but the Earth's orbit is not completely circular).

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Atractus cerberus, Atractus esepe & Atractus pyroni: Three new species of Groundsnake from Ecuador.

Groundsnakes of the genus Atractus are found across Central and South America. These Snakes are Colubrids, the group that also includes Rat Snakes, King Snakes, Water Snakes, Keelbacks and Hognose Snakes, and currently form the most specious genus of Snakes, with over 140 described species. Groundsnakes are mostly small, dull coloured Snakes, making species difficult to tell apart, and the group probably includes numerous cryptic species (species which are impossible or nearly impossible to tell apart by physical examination, but are genetically distinct).

In a paper published in the journal ZooKeys on 15 March 2017, Alejandro Arteaga of Tropical Herping, Konrad Mebert of the Departamento de Ciências Biológicas at the Universidade Estadual de Santa Cruz, Jorge Valencia of the Fundación Herpetológica Gustavo Orcés, Diego Cisneros-Heredia of the Laboratorio de Biología Evolutiva and Laboratorio de Zoología Terrestre at the Universidad San Francisco de Quito, Nicolás Peñafiel of the Centro de Investigación de la Biodiversidad y Cambio Climático at the Universidad Tecnológica Indoamérica, Carolina Reyes-Puig of the División de Herpetología at the Museo Ecuatoriano de Ciencias Naturales, José Vieira-Fernandes, also of Tropical Herping, and Juan Guayasamin, also of the Laboratorio de Biología Evolutiva and Laboratorio de Zoología Terrestre at the Universidad San Francisco de Quito, and the Centro de Investigación de la Biodiversidad y Cambio Climático at the Universidad Tecnológica Indoamérica, describe three new species of Groundsnake, based upon a genetic survey of specimens in museum and university collections assigned to the genus. 

The first new species described is named Atractus cerberus, in reference to the Triple-headed Dog that guards the Gates of the Underworld in Greek mythology, as the species is described from two specimens collected from the gates of the Refinería del Pacífico, a large oil-processing plant and somewhat Underworld-like environment. The two specimens from with the species is described are both males, and are 235 and 345 mm in length. The Snakes are dark brown in colour, with five faint longitudinal darker stripes on their upper surface, and yellow beneath with brown speckles. The area where the specimens were found was in a deciduous lowland forest surrounded by dry shrubland, three kilometres from the sea. As the woodland where the species was found is highly fragmented and covers less than 50 square kilometres in the Refugio de Vida Silvestre Pacoche of Manabí Province, Arteaga et al. recomend that the species be considered Critically Endagered under the terms of the  International Union for the Conservation of Nature's Red List of Threatened Species.

The two known specimens of Atractus cerberus. Arteaga et al. (2017).

The second new species is named Atractus esepe, which derives from 'sp.' the abbreviation of species used by biologists, in reference to how unknown Groundsnkes are refered toin the field (i,e, Atractus sp.). The species is known from two specimens, one male and one female, collected from a secondary evergreen lowland forest from the Caimito area of Esmeraldas Province, roughly 1.3 km from the sea. The specimens are 364 and 294 mm in length, with a dark upper surface with six darker longitudinal lines, dark spots on their sides and white undersides with brown speckles. 

Atractus esepe, male specimen. Arteaga et al. (2017).

The final species described is named Atractus pyroni, in honour of the herpetologist Alexander Pyron, for his invaluable contribution to systematics and evolution of the world’s Reptiles. The species is described from a single female specimen, collected from a road between pasture and remnant montane cloudforest at an altitude of 2026 m, between Balzapamba and Bilován in Bolívar Province. The specimen is 477 mm in length, and black in  colour with a double row of yellow scales on its back. 

Atractus pyroni female specimen. Arteaga et al. (2017).

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Tuesday, 17 October 2017

Elephants kill four Rohingya refugees in Cox's Bazar, Bangladesh.

A mother and her three children have died and several other people have been injured, including the children's father, after a herd of Elephants entered the Balukhali Refugee Camp in the Chittagong Hills near Ukhiya in the Cox's Bazar District of Bangladesh on Saturday 14 October 2017. This is the third such incident in recent weeks, with at least seven deaths having occurred in the previous incidents.

The Balukhali Refugee Camp in Cox's Bazar, Bangladesh. NPR.

Over half a million Rohingya Muslims have fled Myanmar in the last two months, the result of a (somewhat uneven) conflict with the Myanmar armed forces,which have targeted whole communities in response to alleged attacks on security posts, a conflict that has been widely condemned as ethnic cleansing. The majority of these refugees have arrived in Bangladesh, a country that has accepted them, but struggled to meet their needs. Thus many of the refugees have settled in makeshift camps in districts close to the border with Myanmar, many of which have been cleared from forest, thus both creating space for new homes and providing building materials. 

Such camps are not good for wildlife in the areas where they are built. Many animals will simply flee such incursions, or, if unable to, are likely to end up in the cooking pots of hungry migrants. Elephants, however, are a somewhat different proposition. They are large animals, not used to being challenged by other animals in their home ranges, and typically live in matriacrchal herds of up to a hundred, with herds holding large territories, criss-crossed by Elephant trails. A herd of Elephants encountering a new Human settlement, particularly a hurriedly-built, poorly defended structure, are unlikely to attempt to go round it, and are quite likely to maximise the damage they cause to show their displeasure.

Herd of Elephants in Assam State, India. Perfect World Foundation.

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Monday, 16 October 2017

The Orionid Meteor Shower.

The Orionid Meteors are a prolific meteor shower appearing in late October each year and peaking on the nights of 20-22 October, when the shower can produce 50-70 meteors per hour, originating in the constellation of Orion (above and to the right of Orion's right shoulder). This makes them both one of the more prolific meteor showers, and one of the easiest for an amateur enthusiast to locate the radiant of (apparent point of origin). This year's display promises to be particularly good, as the New Moon falls on 20 October 2017, so that there should be little moonlight to interfere with visibility.

 The radiant of the Orionid Meteors. Stary Night/

The shower is caused by the Earth passing through the trail of Halley's Comet (technically Comet P1/Halley), and encountering dust from the tail of this comet. The dust particles strike the atmosphere at speeds of over 200 000 km per hour, burning up in the upper atmosphere and producing a light show in the process. The Earth does not need to pass close to Halley's Comet for the meteor shower to occur, it simply passes through a trail of dust from the comet's tail that is following the same orbital path. Halley's Comet only visits the Inner Solar System once every 75 years, last doing so in 1986. 

The calculated orbit and position on 16 October 2017 of Comet P1/Halley. The Sky Live 3D Solar System Simulator.

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Orange cloud covers much of UK.

Much of the UK has been covered by a thick dust cloud today, reducing light levels and turning the sky an orange colour. The cloud was originally seen over the southwest of the country, and moved to the north and east.

Orange sky over London's Shard Building. Dominic Lipinski/PA.

The cloud is thought to have been caused by dust laden winds associated with former Hurricane Ophelia, a tropical storm over the Atlantic currently moving towards the UK. The dust is thought mostly to have originated from the Sahara; dust plumes from the Sahara frequently blow out over the Atlantic, and are a significant contributor to soils in the Amazon Basin, however these dust plumes are not generally blown back towards Europe unless an unusual wind pattern, such as that caused by Ophelia, crosses their path.

 The path and strength of Hurricane Ophelia. Thick line indicates the past path of the storm (till 3.00 pm GMT on Monday 16 October 2017), while the thin line indicates the predicted future path of the storm, and the dotted circles the margin of error at six and twelve hours ahead. Colour indicated the severity of the storm. Tropical Storm Risk.

Tropical storms are caused by the warming effect of the Sun over tropical seas. As the air warms it expands, causing a drop in air pressure, and rises, causing air from outside the area to rush in to replace it. If this happens over a sufficiently wide area then the inrushing winds will be affected by centrifugal forces caused by the Earth's rotation (the Coriolis effect). This means that winds will be deflected clockwise in the northern hemisphere and anti-clockwise in the southern hemisphere, eventually creating a large, rotating Tropical Storm. They have different names in different parts of the world, with those in the northwest Atlantic being referred to as hurricanes.

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