Sunday, 17 June 2018

Landslide kills four artisanal gold miners in Honduras.

Four miners have died and another five have been injured in a landslide at an artisanal gold mine near El Retiro in Olancho Department, Honduras, on Saturday 16 June 2018. The incident reportedly happened at the end of the day, when the miners were cleaning ore extracted during the day. The miners have not been identified, but they have been described as two men and two women.

The approximate location of a Honduran mine where four workers were killed in a landslide on 16 June 2018. Google Maps.

Artisanal mining is widespread in Olancho Department, where subsistence farmers often supplement their income in one of the poorest countries in the world. Such mines are technically illegal, and are generally constructed without any consideration to health and safety measures.

It is unclear whether the landslide was triggered by the activities of the miners, or whether it was caused by rainfall. Landslides are a common problem after severe weather events, as excess pore water pressure overcomes the sediments cohesion and allows it to flow downhill. Approximately 90% of all landslides are caused by heavy rainfall. June falls in the rainy season in southern Honduras, which lasts from May to September.

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Magnitude 5.5 Earthquake off the coast of Zambales Province, The Philippines.

The United States Geological Survey recorded a Magnitude 5.5 Earthquake at a depth of 34.3 km roughly 37 km offshore of Zambales Province on southwestern Luzon Island, the Philippines, slightly after 5.45 pm local time (slightly after 9.45 am GMT) on Sunday 17 June 2018. There are no reports of any damage or injuries associated with this event, though it was felt across much of the southwestern part of Luzon. 
The approximate location of the 17 June 2018 Zambales Earthquake. USGS.
The geology of the Philippines is complex, with the majority of the islands located on the east of the Sunda Plate. To the east of this lies the Philippine Sea plate, which is being subducted beneath the Sunda Plate (a breakaway part of the Eurasian Plate); further east, in the Mariana Islands, the Pacific Plate is being subducted beneath the Philippine Sea Plate. This is not a smooth process, and the rocks of the tectonic plates frequently stick together before eventually being broken apart by the rising pressure, leading to Earthquakes in the process.
 Subduction beneath the Philippines. Yves Descatoire/Singapore Earth Observatory.
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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Evacuations ordered after eruption on Mount Mayon, Luzon Island.
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Saturday, 16 June 2018

Aurelia sp.: Over 800 bathers stung by Moon Jellyfish on central Florida coast in three days.

A bloom of Moon Jellyfish, Aurelia sp., on the central Florida coast has caused problems for bathers this week, with over 800 people stung in a three day period from Saturday 9 to Monday 11 June 2018. The problem first came to the attention of coast guards on Saturday 9 June, when 107 people reported being stung. This number rose sharply the following day, when 523 people were stung, with a further 180 people stung on Monday 11, bringing the total to 810. Fatalities from Moon Jellyfish are extremely rare, but the stings are painful and unpleasant, and can cause distress to those who suffer them.

A Moon Jellyfish, Aurelia sp.. Key West Aquarium.

Members of the genus Aurelia are inshore Jellyfish found in coastal waters in tropical, subtropical and temperate seas around the world. They are large Jellyfish, reaching a maximum size of about 40 cm in diameter, a slight purplish tinge and four large, horseshoe-shaped gonads. Moon Jellyfish often undergo major blooms in the summer months, due to their tolerance for low oxygen conditions, which are harmful to most of their competitors and predators (Fish and large invertebrates), enabling them to dominate environments where these animals are excluded. This tends to lead to summer blooms in enclosed areas (heat and lack of exchange with the open ocean can rapidly deplete oxygen levels), which can be worse in areas where pollution from agriculture or other Human activities leads to eutrophication (excess nutrients which can lead to eutrophication and the rapid growth of blooms of Algae, Bacteria or other micro-organisms, which absorb oxygen from the water leading Fish and other aquatic organisms to asphyxiate). 
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Eruption on Mount Kerinci, Sumatra.

The Darwin Volcanic Ash Advisory Centre reported an eruption on Mount Kerinci in West Sumatra, on Sunday 10 June 2018, which produced an ash column that rose to a height of 4 km and drifted to the west. Kerinci ia a stratovolcano (cone shaped volcano made up of layers of ash and lava), in the Barisan Mountains, which run along the western side of Sumatra. It reaches 3800 m above sealevel, making it the highest point on the island of Sumatra, the second highest point in Indonesia (after Puncak Jaya, a fold mountain in West Papua Province, which forms the highest point on any island in the world) and the second highest island volcano in the world (after Mauna Kea in Hawai'i). It is a fairly active volcano, with frequent small eruptions, though major eruptions are rare, located within the Kerinci National Park, and is a popular tourist attraction.

Mount Kerinci seen from the south in 2008. Wikimedia Commons.

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.

The two plates are not directly impacting one-another, 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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Siberian river turned red pollution following failure of mine tailings pond.

A river in Siberia has turned red after a mine tailings pond failed this week. The Daldykan River in the north of the Krasnoyarsk Krai (Republic) in Siberia was effected by runoff from the Nornickel operated Nadezhda Metallurgical Plant, which is a deep red colour due to a high iron salt content.

The River Daldykan in northern Krasnoyarsk, turned red by iron salts from a nickel plant tailings pond. Siberian Times.

The Nadezhda Metallurgical Plant is a Soviet era installation, which were largely constructed without consideration of environmental issues in a drive to industrialise rapidly. The plant was fined an undisclosed amount by environmental watchdog Rosprirodnadzor in 2016 following a similar incident, and has reportedly undergone some environmental remediation work since. However, while the size of the fine has not been revealed, the maximum fine that could have been imposed would have been 40 000 roubles (US$650), a fine of limited consequence to a company such as Nornickel, which has estimated about US$16 500 000 000, and it is unclear to what extent the environmental watchdog could genuinely sanction the company, which is 28% owned by Russian president Vladamir Putin.

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Asteroid 2015 DP155 passes the Earth.

Asteroid 2015 DP155 passed by the Earth at a distance of about 3 455 200 km (8.96 times the average distance between the Earth and the Moon, or 2.30% of the distance between the Earth and the Sun), slightly after 5.50 am GMT on Monday 11 June 2018. There was no danger of the asteroid hitting us, though were it to do so it would have presented a significant threat. 2015 DP155 has an estimated equivalent diameter of 94-300 m (i.e. it is estimated that a spherical object with the same volume would be 90-300 m in diameter), and an object at the upper end of this range 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 about 65 000 times as powerful as the Hiroshima bomb. Such an impact would result in an impact crater over 4.5 km in diameter and devastation on a global scale, as well as climatic effects that would last years or even decades.

The calculated orbit of 2015 DP155. Minor Planet Center.

2015 DP155 was discovered on 17 February 2015 by the University of Hawaii's PANSTARRS telescope. The designation 2015 DP155 implies that the asteroid was the 3890th object (object P155) discovered in the second half of February 2015 (period 2015 D).   

2015 DP155 has a 552 day orbital period and an eccentric orbit tilted at an angle of 5.38° to the plane of the Solar System, which takes it from 1.02 AU from the Sun (i.e. 102% of he average distance at which the Earth orbits the Sun) to 1.60 AU from the Sun (i.e. 160% 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). This means that close encounters between the asteroid and Earth are extremely common, with the last having occurred in April 2015 and the next predicted in June 2021. As an asteroid probably larger than 150 m in diameter that occasionally comes within 0.05 AU of the Earth, 2015 DP155 is also classified as a Potentially Hazardous Asteroid. 2015 DP155 also has occasional close encounters with the planet Mars, with the last having occurred in March 2004, and the next predicted for April 2026.

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Chinese city hit by rain of sea creatures.

The city of Qingdao in Shandong Province, China, was hit by a rain of sea creatures during a storm on Wednesday 13 June 2018. A variety of animals were observed to fall on the city, including Octopus, Starfish and Crustaceans. The creatures fell amid a storm which brought high winds and flooding to the city, knocking over a number of trees but which is not reported to have caused any serious damage or casualties.

An Octopus on the windscreen of a car following a rain of sea creatures during a storm in Qingdao, China, on 13 June 2018. Shanghailist/Weibo.

Rains of aquatic animals occur when tornadoes over bodies of water suck up volumes of water including the Fish. That this could lead to rains of Fish very far from the site seems counter intuitive, but tornadoes are capable of lifting heavy objects such as cars and even houses and throwing them considerable distances, and small animals such as Fish can be thrown kilometres into the air by such events, falling to Earth a long way from the site where they were picked up.

Flooding in Qingdao on 13 June 2018. News 163.

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