Sunday, 19 November 2017

Significant spill from Keystone XL Pipeline in South Dakota.

Part of the Keystone XL Pipeline has been closed down after a leak was discovered about 35 km to the south of the Ludden Pump Station in Marshall County, South Dakota, on Thursday 13 November 2017. The spill was detected by pipeline operators TransCanada, who noticed a drop in pressure in the pipeline and shut down flow while the situation was investigated.  The leak was originally thought to have been quite small, with about 210 000 barrels (333 900 000 litres) of oil having been lost, however inspection of the site has suggested a much larger loss, with current estimates running at 600 000 barrels (953 900 000 litres) and environmental groups concerned that the real figure will eventually be found to be much higher. This discrepancy is thought to have been caused by the dense nature of the bituminous oil running through the pipeline, which will have resulted in a slower drop in pressure that would happen with a lighter oil fraction.

The November 2017 South Dakota spill. TransCanada.

The Keystone XL Pipeline is intended to carry crude oil from tar sands deposits in Alberta, Canada, to refineries in Illinois and Texas in the US. It been opposed at almost every stage by environmental groups concerned about the possibility of leaks such as this week's one in South Dakota, the environmentally destructive nature of extracting oil from tar sands, and the contribution of a major expansion in hydrocarbons production to atmospheric carbon dioxide and global warming. These concerns led former American President Barrack Obama to halt the construction of the pipeline in 2015, however this order was rescinded by incoming President Donald Trump in March 2017. The pipeline currently pumps oil from Alberta to a refinery in Patola, Illinois, with construction of the final leg to Texas underway.

Protests against the construction of the Keystone XL Pipeline in Washington DC in 2014. Kristina Banks/Huffington Post.

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Asteroid 2017 WD passes the Earth.

Asteroid 2017 WD passed by the Earth at a distance of about 715 200 km (1.86 times the average distance between the Earth and the Moon, 0.48% of the distance between the Earth and the Sun), slightly before 11.55 am GMT on Monday 13 November 2017. There was no danger of the asteroid hitting us, though were it to do so it would not have presented a significant threat. 2017 WD has an estimated equivalent diameter of 4-15 m (i.e. it is estimated that a spherical object with the same volume would be 4-15 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 2017 WD. Minor Planet Center.

2017 WD was discovered on 16 November 2017 (three days after its closest approach to the Earth) by the University of Arizona's Mt. Lemmon Survey at the Steward Observatory on Mount Lemmon in the Catalina Mountains north of Tucson. The designation 2017 WD implies that the asteroid was the forth object (object D) discovered in the second half of November 2017 (period 2017 W).  

2017 WD has a 1082 day orbital period and an eccentric orbit tilted at an angle of 3.79° to the plane of the Solar System, which takes it from 0.92 AU from the Sun (i.e. 92% of he average distance at which the Earth orbits the Sun) to 3.20 AU from the Sun (i.e. 320% of the average distance at which the Earth orbits the Sun, slightly more than twice the distance at which the planet Mars orbits). 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).

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Saturday, 18 November 2017

Flooding and landslide kill nineteen in the Attica Region of Greece.

Nineteen people have died and a further three are missing following a series of flash floods and landslides in the Attica Region of Greece since Tuesday 14 November 2017. Many houses and businesses have been inundated in the towns of Mandra, Nea Peramos and Megara, and part of the Athens-Corinth highway has been washed away near Athens.

Flash flood in Mandora earlier this week. Valarie Gache/APP/Getty Images.

Storm systems form due to heating of air over the sea, usually in tropical zones, though Herwart formed off the coast of southern Scandinavia. As the air is heated the the air pressure drops and the air rises, causing new air to rush in from outside the forming storm zone. If this zone is sufficiently large, then it will be influenced by the Coriolis Effect, which loosely speaking means the winds closer to the equator will be faster than those further away, causing the storm to rotate, clockwise in the northern hemisphere and anticlockwise in the southern hemisphere.

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Magnitude 5.4 Earthquake in North Gyeongsang Province, South Korea.

The United States Geological Survey reported a Magnitude 5.4 Earthquake at a depth of 10.0 km about 10 km northwest of the city of Pohang in North Gyeongsang Province, South Korea, slightly before 2.30 pm, local time (slightly before 5.30 am GMT) on Wednesday 15 November 2017. The quake caused extensive damage to buildings in and around Pohang, with over a thousand buildings destroyed or damaged and more than 1500 people made homeless and 57 reported injuries, with ten people hospitalised and two described as being in critical conditions. People have reported feeling the event across South Korea, and it is likely that it was also felt in North Korea. The event was followed by at least 45 aftershocks.

Damage in Pohang, South Korea, following the 15 November 2017 Earthquake. Min Kyung-suck/Newsis/AP.

Korea lies on the southern part of the Amurian Plate, a breakaway section of the Eurasian Plate that also underlies parts of China, Japan, and the Russian Far East. The border with the Eurasian Plate lies to the east of the Korean Peninsula; this is a divergent margin along which new seafloor is being created, pushing the Eurasian and Amurian Plates apart. The Amurian Plate is also moving south relative to the Eurasian Plate, creating extra stresses along the margin between the two plates. Despite this significant Earthquakes in South Korea are not common events, and this is the second largest ever recorded there.

 Map of Plate Framework in the Northeast Asia. Study area is depicted by open red box. Boundaries of the Okhotsk (OK) and Amur (AM) plates are shown. Surrounding plates include Eurasia (EU), North America (NA), Pacific (PA), Philippine Sea (PS), and Yangtze (YA). Black vectors give model velocities (with numbers in mm/a) relative to plate whose identifier is underlined. Black circles are locations of Euler poles. Akira Takeuchi (2013).

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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Thursday, 16 November 2017

Eruption on Mount Dempo, Sumatra.

The Badan Nasional Penangulanggan Bencana (Indonesia's Disaster Mitigation Agency)has reported an eruption on Mount Dempo, a 3173 m stratovolcano (cone shaped volcano made up of layers of ash and lava) in South Sumatra, on Thursday 9 November 2017. The eruption began slightly after 4.50 pm local time, and produced a dense ash plume that rose about a kilometre above the summit of the volcano and drifted to the south.

Ash column over Mount Dempo, Sumatra, on 9 November 2017. Detik News.

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

  The Subduction zone beneath Sumatra. NASA/Earth Observatory.

This does not happen at a 90° angle, as occurs in the subduction zones along the western margins of North and South America, but at a steeply oblique angle. This means that as well as the subduction of the Indo-Australian plate beneath the Sunda, the two plates are also moving past one-another. This causes rifting within the plates, as parts of each plate become stuck to the other, and are dragged along in the opposing plate's direction. The most obvious example of this is the Sumatran Fault, which runs the length of Sumatra, with the two halves of the island moving independently of one-another. This fault is the cause of most of the quakes on the island, and most of the island's volcanoes lie on it.

 The movement of the tectonic plates around Sumatra. NASA/Earth Observatory.

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Wednesday, 15 November 2017

The Leonid Meteors.

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, and viewing could be good this year as the shower peaks just before the New Moon on 18 November. 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.

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. 

 Image of Comet 55P/Tempel-Tuttle taken in February 1998 from the National Astronomical Observatory of Japan. Cometography.

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 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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Ocyale ghost: A new species of Wolf Spider from Madagascar.

Wolf Spiders, Lycosidae, are large, active Spiders that do not build webs, ambushing animals that passes close to their burrows or actively seeking out and chasing down prey. They have large prominent eyes, and a habit of carrying their eggs in a sack on their abdomens. Members of the genus Ocyale are found in Africa, Asia and the America's though it is thought likely that all American and possibly Asian species may have been placed in this genus erroneously.

In a paper published in the European Journal of Taxonomy on 3 October 2017, Merlijn Jocque of the Biodiversity Inventory for Conservation, Operation Wallacea, and Aquatic and Terrestrial Ecology at the Royal Belgian Institute of Natural Sciences, Siel Wellens, also of Biodiversity Inventory for Conservation and Operation Wallacea, J Andianarivosoa and Felix Rakotondraparany of Mention Zoologie et Biologie Animale at the Université d’Antananarivo, Sam The Seing of Development and Biodiversity Conservation Action for Madagascar, and Rudy Jocqué of the Royal Museum for Central Africa, describe a new species of Ocyale from Mahajanga Province in Madagascar.

The new species is named Ocyale ghost, in reference to its white colour and in addition the white Wolf 'Ghost in the book Game of Thrones by George R.R. Martin. It is a moderately large Spider, with males reaching 16.76–19.45 mm and females 16.47–22.01 mm, creamy white in colour with darker spots and yellow rings around the eyes. The species was found only on the white sandy beaches surrounding Lake Matsedroy.

Ocyale ghost, female photographed at type locality. Jocque et al. (2017).

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