Friday, 22 June 2018

Seven dead in Mexico flooding.

Seven people have died in flooding in Mexico this week. On Friday 15 June 2018 a fourteen-year-old boy was swept into a storm drain in Mexico City and drowned, On Tuesday 19 June a woman and a teenage girl died of carbon monoxide poisoning while trapped in a car caught in floodwaters in Aguascalientes, while a landslide killed a man in Guanajuato. Landslides 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.On Wednesday 20 June a forty-year-old man drowned in Mexico City, and two people were electrocuted when they touched power cables after climbing onto buildings to escape floodwaters, one in Mexico City and another in the city of Matamoros in Tamaulipas State. Flooding has also been reported in Texas as far north as Houston.

Cars caught in floodwater in Aguascalientes on Tuesday 19 June 2018. Mexico Daily News.

Rainfall in eastern Mexico an southern Texas is driven principally by evaporation of water from the Caribbean, an area which has been suffering exceptionally high temperatures this year. However the flooding has also been linked to rapid urban expansion in many area, which has led to building on areas of historic wetlands, reducing the ability of the ground to absorb water and leading to surface flooding.

Flooding in Weslaco, Texas, on 20 June 2018. Joel Martinez/The Monitor/AP.

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Wednesday, 20 June 2018

Warning issued after bloom of Lion's Mane Jellyfish wash up on Lancashire coast.

A warning has been issued by the Lytham and Blackpool Coastguard after dozens of Lion's Mane Jellyfish, Cyanea capillata, washed up on the coast between Fylde and Lytham St Annes this week. The Jellyfish are potentially dangerous if touched, as they can still sting when dead, though the stings are no worse than those of Bees or Wasps, and not generally dangerous unless people have an allergic reaction. The Jellyfish are far more dangerous when encountered in the water, as their tentacles can entangle swimmers, resulting in large numbers of stings, which can cause the swimmer to go into shock and drown.

A Lion's Mane Jellyfish, Cyaneae capillata, off the coast of Sweden in 2016. Wikimedia Commons.

The Lion's Mane Jellyfish is the largest known species of Jellyfish, reaching over 2 m in diameter and with tentacles that can be more than 30 m in length. They are exclusively found in cooler temperate waters around the North Atlantic, North Pacific, Arctic Ocean and Baltic Sea. They are pelagic, able to swim against currents under their own energy, rather than drifting as many Jellyfish do, and spend most of their lives in open water, but they move into coastal waters towards the end of their annual life-cycle, when the (sexual) medusae produce eggs, which in turn hatch into a polyp which attaches to the seafloor in shallow waters, from which new medusae bud off asexually.

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Suspected Foot-and-Mouth outbreak in Botswana.

Authorities in Botswana have issued a warning to trading partners after a possible Foot-and-Mouth outbreak in Ngamiland District, in the northwest of the country. As yet only five animals have shown symptoms of the disease, and these have yet to be confirmed by laboratory testing, but all slaughter and movement of animals from the Sehithwa, Toteng, Bodibeng, Kareng and Semboyo areas has been suspended as a precaution, as has all exportation of meat from animals in Ngamiland District, and a program of vaccinations begun as a precaution.

Cattle in Ngamiland. The Voice.

Foot-and-Mouth is caused by Aphthae epizooticae, a form of Picornavirus (single-stranded RNA virus with an icosahedral capsule but no lipid membrane), i.e. a member of the group that also causes Hepatitis A, which is generally transmitted through physical contact, though it can be passed on by aerosol, or by with inanimate objects that have been in contact with infected animals, notably Human clothing. The disease is seldom fatal in adult animals, but causes ulceration of the mouth and feet, which can lead to a long-term decline in the health of infected animals, including lameness and weight loss, for which reason many countries impose a complete ban on importing animals and products from areas where the disease is present, with severe economic consequences.

Cattle production is a mainstay of the Botswanan rural economy, with thousands of jobs dependent upon it, and significant exports of beef to Europe, as well as beef and livestock to other Southern African countries. This industry has repeatedly been struck by outbreaks of Foot-and-Mouth and other Cattle diseases endemic to the region, which, if not contained rapidly, tend to result in large scale culls of livestock (as in other Cattle-farming nations). In 1995 an outbreak of Cattle Lung Disease led to the slaughter of the entire herd of Ngamiland District.

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Flooding kills at least eighteen in Abidjan, Côte d'Ivoire.

At least eighteen people died in flooding in Abidjan, Côte d'Ivoire, on Monday 18-Tuesday 19 June 2018, with over a hundred needing to be rescued by emergency services and many more escaping on their own. The flooding was caused by torrential rain overnight, associated with the West African Rainy Season, which has been particularly severe this year due to high temperatures over the Gulf of Guinea, leading to more water evaporating from the sea surface, and therefore more falling on land. 

The aftermath of a flash flood in Abidjan on 19 June 2018. Luc Gnago/Reuters.

The rains began at about 11.00 pm, and persisted till about 6.00 am, causing a sting of flash floods that in places reached 2.5 m deep. Abidjan has become increasingly prone to flash flooding due to rapid urban expansion in the area (the population of Côte d'Ivoire has doubled since 1990), which is built on an area of historic coastal wetlands, preventing rainwater from draining into the soil and raising the dangers of flooding in the city.

June falls in the middle of the rainy season in Abidjan, with the city receiving an average of 568.1 mm of rain during the month. West Africa has a distinct two season climatic cycle, with a cool dry season during the northern winter when prevalent winds blow from the Sahara to the northeast, and a warm rainy season during the northern summer when prevalent winds blow from the Atlantic Ocean to the southwest. These warm winds from the Atlantic are laden with moisture, which can be lost rapidly when the air encounters cooler conditions, such as when it is pushed up to higher altitudes by the Ivorian plateaux.

 Rainfall and prevalent winds during the West African dry and rainy seasons. Encyclopedia Britanica.

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Asteroid 2018 LD1 passes the Earth.

Asteroid 2018 LD1 passed by the Earth at a distance of about 601 400 km (1.58 times the average  distance between the Earth and the Moon, or 0.02% of the distance between the Earth and the Sun), at about 4.00 pm GMT on Thursday 14 June 2018. There was no danger of the asteroid hitting us, though were it to do so it would not have presented a significant threat. 2018 LD1 has an estimated equivalent diameter of 11-34 m (i.e. it is estimated that a spherical object with the same volume would be 11-34 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 30 and 10 km above the ground, with only fragmentary material reaching the Earth's surface.

The calculated orbit of 2018 LD1. Minor Planet Center.

2018 LD1 was discovered on 5 June 2018 (nine days before its closest approach to the Earth) by the University of Hawaii's PANSTARRS telescope. The designation 2018 LD1 implies that the asteroid was the 29th object (object D1) discovered in the first half of June 2018 (period 2018 L).   

2019 LD1 has a 929 day orbital period and an eccentric orbit tilted at an angle of 0.35° to the plane of the Solar System, which takes it from 0.91 AU from the Sun (i.e. 91% of he average distance at which the Earth orbits the Sun) to 2.82 AU from the Sun (i.e. 282% of the average distance at which the Earth orbits the Sun, and further from the Sun than the planet Mars). 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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Magnitude 5.9 Earthquake in Osaka Prefecture results in three fatalities and over 200 injuries.

The Japan Meteorological Agency recorded a Magnitude 5.9 Earthquake at a depth of about 10 km, beneath Osaka Prefecture on Honshū Island, slightly before 8.00 am Japan Standard Time  on Monday 18 June 2018 (slightly before 11.00 pm on Sunday 17 June GMT). The Earthquake is known to have resulted in three fatalities, a nine year old girl and two men in their eighties, as well as at least 217 injuries, and left about 170 000 households without power, as well as causing severe disruption to public transport networks.

Damaged goods in a supermarket following the 18 June 2018 Osaka Earthquake. Reuters.

Japan has a complex tectonic situation, with parts of the country on four different tectonic plates. Eastern Honshū area lies on the boundary between the Pacific, Eurasian and Philippine Plates, where the Pacific Plate is passing beneath the Eurasian and Philippine Plates as it is subducted into the Earth. This is not a smooth process; the rocks of the two plates constantly stick together, only to break apart again as the pressure builds up, causing Earthquakes in the process.

The movement of the Pacific and Philippine Plates beneath eastern Honshū. Laurent Jolivet/Institut des Sciences de la Terre d'Orléans/Sciences de la Terre et de l'Environnement.

\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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Northern Solstice 2018.

The Northern) Solstice falls on Thursday 21 June in 2018, the day on which the Sun rises highest in the sky and the longest day of the year in the Northern Hemisphere (where it is the Summer Solstice) and the day on which the Sun rises lowest in the sky and the shortest day in the Southern Hemisphere (where it is the Winter Solstice). Up until this date the days have been growing longer in the Northern Hemisphere and shorter in the Southern Hemisphere since the Southern Solstice in December 2017 (which is the Winter Solstice in the Northern Hemisphere and Summer Solstice in the Southern Hemisphere), but after it the situation will be reversed, with days growing steadily shorter in the Northern Hemisphere and longer in the Southern Hemisphere until the next Southern Solstice in December this year..

The solstices are entirely a product of variation in the Earth's rotation on its axis, which is at an angle of 23.5° to the plain of the Earth's orbit about the Sun. This means that in December the Earth's Southern Pole is tilted towards the Sun, while the Northern Pole is tilted away from it. This means that around the Southern Solstice the Southern Hemisphere is receiving radiation from the Sun over a longer part of the than the Northern, and at a steeper angle (so that it to pass through less atmosphere to reach the planet), creating the southern summer and northern winter.
The tilt of the Earth at the Northern Solstice. Wikimedia Commons.

The solstices are fairly noticeable astronomical events, and tied to the seasons which govern the life cycles of life on Earth, and they have been celebrated under different names by cultures across the globe, but most notably by those at higher latitudes, who are more profoundly affected by the changes of the seasons.

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