Wednesday, 14 November 2018

The Leonid Meteor Shower.

Each year between 15 and 18 November (approximately), typically peaking between midnight and dawn on 17 November, the the Earth encounters the Leonid Meteors, one of the more spectacular of the annual meteor showers, though with the waxing quarter Moon falling on 15 November this year viewing will be slightly less than optimal. Unlike most such showers, which are essentially composed of dust particles, the Leonids comprise particles of up to 8 mm across and up to 85 g in mass, leading to some spectacular fireballs, and each year the shower is thought to deposit 12-13 tonnes of material on the Earth. The Leonid Meteor Shower is so called because the meteors they appear to originate in the constellation of Leo. (Note a meteor is a 'shooting star', a piece of material visibly burning up in the atmosphere and detectable via the light it produces when doing this; a meteorite is a piece of rock that has fallen from the sky and which a geologist can physically hold; and an asteroid is a chunk of rock in orbit about the Sun, to small to be regarded as a planet.

The radiant point (apparent point of origin) of the Leonid Meteors. Bronberg Weather Station.

The Leonid Meteors are thought to originate from the tail of Comet 55P/Tempel-Tuttle, which orbits the Sun every 33 years, on an orbit that brings it slightly within the orbit of the Earth then out to slightly beyond the orbit of Uranus. Comets are composed largely of ice (mostly water and carbon dioxide), and when they fall into the inner Solar System the outer layers of this boil away, forming a visible tail (which always points away from the Sun, not in the direction the comet is coming from, as our Earth-bound experience would lead us to expect). Particles of rock and dust from within the comet are freed by this melting (strictly sublimation) of the comet into the tail and continue to orbit in the same path as the comet, falling behind over time. 

 The orbit and current position of Comet 55P/Tempel-Tuttle. The Sky Live 3D Solar System Simulator.

The material in the meteor shower is densest close behind the comet, and, since Comet 55P/Tempel-Tuttle has a 33 year orbit, the Leonid Meteor Shower has a 33-year cycle, with a particularly spectacular display every thirty-third year, then a gradual decline in meteor number till the end of the cycle. The last such peak year was in 1998.

 Comet 55P/Tempel-Tuttle imaged on 26 January 1998. Image is a composite of several stacked images, with the dotted lines being stars that have moved between exposures. Nick James/The Astronomer.

Comet 55P/Tempel-Tuttle was discovered in December 1865 by German astronomer Wilhelm Tempel, and independently in January 1866 by the American Horace Parnell Tuttle. The designation 55/P implies that it is a Periodic Comet (comet with an orbital period of less than 200 years), and that it was the 55th such body discovered. As a Comet with a Period of less than 200 years and more than 20 years it is also regarded as a Halley-type Comet.

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Tuesday, 13 November 2018

Magnitude 2.3 Earthquake near Leominster in Herefordshire, England.

The British Geological Survey recorded a Magnitude 2.3 Earthquake at a depth of 14 km, about 2 km to the east of the town of Leominster in Herefordshire, England, slightly after 11.05 pm GMT on Monday 12 November 2018. This quake is not large enough to have caused any damage or injuries, but may have been felt locally.
The approximate location of the 12 November 2018 Leominster 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 pressures 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
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Raphia gabonica & Raphia zamiana: Two new species of Palms from Gabon and Cameroon.

Palms are an important component of modern tropical ecosystems, with the majority of species (~90%) restricted to tropical rainforests, where they are important understory plants. Palms reach their maximum diversity today in Asia (over 1200 species) and the Americas (about 730 species), but are much less diverse in Africa (about 65 species, less than Madagascar, which has about 200), with only one species native to Europe. Despite Palm Tree being the most familiar form of Palms, there are also climbing, shrubby, and stemless forms. The genus Raphia contains about 20 species of economically significant Palms, noted for their fibrous leaves (the largest leaves of any known Plant) used in making thatch, furniture and matting, and edible fruit. Almost all species of Raffia are found in Africa, with one species found in Central and South America, and one in Madagascar. Despite their economic significance, Raphia Palms have been little studied by botanists, largely due to their preference for swampy tropical environments.

In a paper published in the journal PhytoKeys on 6 November 2018, Suzanne Mogue Kamga of the Plant Systematic and Ecology Laboratory at the University of Yaoundé, Raoul Niangadouma of the National Herbarium of Gabon, Fred Stauffer of the Conservatoire et Jardin botaniques de la Ville de Genève and the Laboratoire de systématique végétale et biodiversité at the Université de Genève, Bonaventure Sonké, also of the Plant Systematic and Ecology Laboratory at the University of Yaoundé, and Thomas Couvreur of the Université de Montpellier and the Naturalis Biodiversity Centre, describe two new species of Raphia from Gabon and Cameroon.

The first new species described is named Raphia  gabonica, in reference to the country Gabon where it was discovered. The Palm forms a tree with a trunk 3-7 m in height and 20-30 cm in diameter, surmounted by 7-8 leaves, 8-13 m in length. Old leaf sheaths persist and hang down around the trunk, protecting and largely obscuring it. Flowers and fruit are born on pendulous rachillae up to 1.8 m in length. This Palm was found at only two locations, on hill slopes near streams in lowland rainforest in northern Ngounié Province, in Gabon, with a total known area occupied of less than 8 km². For this reason the species is considered to be Endangered under the terms of the International Union for the Conservation of Nature's Red List of Threatened Species

 Raphia gabonica in natural habitat (Alèmbé, Gabon). Notice dry land habitat, not growing in colonies, single stem with curly fibres and long pendulous inflorescences. Thomas Couvreur in Mogue Kamga et al. (2018).

The second new species described is named Raphia zamiana, where 'zamiana' derives from 'Zam' the name for these Palms in Beti, a language spoken in southern Cameroon and northern Gabon. This Palm forms trees with trunks 3-8 m high and 30-40 cm in diameter, surmounted by 10-12 leaves, 12-21 m in length. Again old leaf sheaths persist and hang down around the trunk, protecting and largely obscuring it. Flowers and fruit are born on pendulous rachillae up to 2.8 m in length. This Palm is found in the Atlantic rainforests of central and southern Cameroon, Gabon and probably Equatorial Guinea. The species is extremely abundant and widely used by local populations for its leaves which are used as a construction material, as thatch, and to make furniture, baskets and mats. Its fruit are also harvested and sold as a treatment for hypertension and diabetes. The sap of this species is collected for Palm wine, and edible Grubs are collected from it.

Raphia zamiana. Habitat along the road, with Raoul Niangadouma for scale (Oyem, Gabon). Thomas Couvreur in Mogue Kamga et al. (2018).

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Landslide kills at least ten in Rio de Janeiro State, Brazil.

Ten people, including a three-year-old boy have been confirmed dead following a landslide in the city of Niterói in Rio de Janeiro State, Brazil, on Saturday 10 November 2018. A further four people are missing following the event, with eleven having been rescued alive. The incident occurred after days of heavy rain in the area, when part of a muddy slope collapsed onto a group of residential properties, carrying with it several large boulders. andslides 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.

The scene of a landslide that killed at least ten people in Rio de Janeiro State, Brazil, on Saturday 10 November 2018. EPA.

November sees the start of the rainy season in southern Brazil, a country that has suffered a string of flood and landslide related disasters in recent years. The country has a rapidly growing population, with little effective urban planning, which has led to sprawling urban developments springing up with little thought to natural hazards, and in particular poorer neighbourhoods often expanding up unstable hillsides, with the result that when floods occur (which is not unusual) communities are often quickly overwhelmed. 

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Poacher sentenced to 33 years imprisonment in South Africa.

A poacher has been sentenced to a total of 33 years and 3 months imprisonment following a trial at the Skukuza Regional Court in Mpumalanga Province, South Afica. Patrick Nkuna was arrested in the Krugar National Park in 2015, after shooting at a helicopter belonging to the South African National Parks Service. Nkuma was found guilty of eleven of twelve charges, including four counts of attempted murder, possession of an illegal firearm, entering the park illegally and killing a Black Rhinoceros.

Patrick Nkuna, sentenced to 33 years for crimes related to poaching in the Krugar Nationl Park. The Lowvelder.

Park authorities and private game reserves across Africa and Asia have been struggling with the problem of Rhino poaching for decades, but the problem has become more acute in recent years, with over a thousand killed in South Africa alone in 2017, and over 5500 in the past five years. The country is home to about 20 000 Rhinos, about 80% of the entire African population. The crime is extremely profitable, and widely believed to be controlled by organised crime syndicates, which are thought to have considerable influence over police and court officials in many areas, which results in suspected poachers often being released before they are brought to trial, often with only nominal bail payments.

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Monday, 12 November 2018

Magnitude 5.2 Earthquake in Chine State, Myanmar.

The United States Geological Survey recorded a Magnitude 5.2 Earthquake at a depth of 50.4 km in Chin State, Myanmar, about 47 km to the southwest Indian border, at about 11.45 pm local time (about 5.15 pm GMT) on Saturday 10 November 2018. There are no reports of any damage or injuries following this event, though a large number of people have reported feeling it across much of northeastern India and in parts of Bangladesh.

The approximate location of the 10 November 2018 Chin State Earthquake. USGS.

Myanmar is an area fairly prone to Earthquakes; much of the country lies on the Burma Plate, a small tectonic plate caught between  the Eurasian Plate to the northeast, the Indian Plate to the west and southwest and the Sunda Plate to the southeast. As these larger plates move together the Burma Plate is being squeezed and fractured, with a major fault line, the Kabaw Fault, having formed across much of the north of the country, along which the Burma Plate is slowly splitting. Most Earthquakes in the region are caused by movement on this fault.
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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British citizen dies after contracting Rabies in Morocco.

A British citizen has died of Rabies a few weeks after returning from a holiday in Morocco, according to Public Health England. The unidentified patient apparently sought treatment after being bitten by a Cat while in the North African country, but did not receive the appropriate medication in time, due to an unusually rapid onset of the disease, which typically takes several months to manifest.

Transmission electron microscope image with numerous Rabies virions (small, dark grey, rodlike particles) and Negri bodies (the larger pathognomonic cellular inclusions of rabies infection). Centers for Disease Control and Prevention/Wikimedia Commons.

Rabies is caused by Viruses of the genus Lyssavirus, a member of the Rhabdoviridae Family of negative-sense single-stranded RNA Viruses, which also includes pathogens attacking Fish, Insects and Plants. Rabies is spread through the saliva of infected animals, and causes hydrophobia (fear of water),  anxiety, insomnia, confusion, agitation, abnormal behaviour, paranoia, terror, and hallucinations, followed by paralysis, coma and death in Humans. Many animals (notably Dogs) become extremely aggressive at this stage and will bite anything that comes near them, helping to spread the disease. In Humans, the disease typically has a gestation period of about three months, during which time the disease can be treated by repeated vaccination and doses of human rabies immunoglobulin, though if treatment is not begun within ten days of infection it is less likely to be successful, and once the patient starts to develop symptoms the disease is almost invariably fatal. Any wound thought to have been caused by an infected animal should be washed thoroughly under running water for at least five minutes, before being treated with alcohol or iodine, and immediate medical attention sought.

This is the first case of a patient dying of Rabies in Britain since 2012, when a woman died after being bitten by a Dog in India. The last case of a person dying after catching the disease in the UK happened in 2002, when a Scottish Bat-handler died after being bitten by a Daubenton's Bat (the disease is still endemic in Bats in the UK and other parts of Europe, but being bitten by a Bat is somewhat unusual) the last case the disease in Britain in animal other than a Bat was recorded in 1922, and the last case of a person dying of the disease after contracting it in the UK from an animal other than a Bat occurred in 1902. However the disease is still endemic in many parts of the world, and this week's death is the 24th in Briton since 1946.

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