Monday, 24 July 2017

Asteroid 2017 NS5 passes the Earth.

Asteroid 2017 NS5 passed by the Earth at a distance of about 5 136 000 km (13.4 times the average distance between the Earth and the Moon, or 3.43% of the distance between the Earth and the Sun), at about 8.10 am GMT on Monday 17 July 2017. There was no danger of the asteroid hitting us, though were it to do so it would have presented a considerable threat. 2017 NS5 has an estimated equivalent diameter of 138-410 m (i.e. it is estimated that a spherical object with the same volume would be 138-410 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 3000-165 000 times as powerful as the Hiroshima bomb. Such an impact would result in an impact crater 2-7 km in diameter and devastation on a global scale, as well as climatic effects that would last decades or even centuries.

 Image of 2017 NS5 taken with the iTelescope T17 Deep Field Research Telescope at Siding Spring Observatory in New South Wales on 11 July 2017. The image is a composite of six fifty second exposures, the dotted lines being stars which have moved over the course of the exposures and the asteroid the faint object inset indicated by the arrow. Marian Urbanik/iTelescope/Fotografický občasník.

2017 NS5 was discovered on 10 July 2017 (seven days before its closest approach to the Earth) by the University of Hawaii's PANSTARRS telescope on Mount Haleakala on Maui. The designation 2017 NS5 implies that it was the 143rd asteroid (asteroid S5) discovered in the first half of July 2017 (period 2017 N).

The calculated orbit of 2017 NS1. Minor Planet Center.

2017 NS1 has a 353 day orbital period, with an elliptical orbit tilted at an angle of 44.0° to the plain of the Solar System which takes in to 0.72 AU from the Sun (72% of the distance at which the Earth orbits the Sun; slightly inside the orbit of the planet Venus) and out to 1.23 AU (23% further away from the Sun than the Earth). This means that close encounters between the asteroid and Earth are fairly common, with the last thought to have happened in July 2016 and the next predicted in July 2018. 2017 NS1 also has occasional close encounters with the planet Venus, with the next predicted for February 2148. Although it does cross the Earth's orbit and is briefly further from the Sun on each cycle, 2017 NS1 spends most of its time closer to the Sun than we are, and is therefore classified as an Aten Group Asteroid. As an asteroid probably larger than 150 m in diameter that occasionally comes within 0.05 AU of the Earth, 2017 NS1 is also classified as a Potentially Hazardous Asteroid.

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Caliothrips chiapas: A new species of Thrips from Mexico.

Thrips are tiny (usually less than one millimetre) Insects with greatly reduced wings that resemble feathery stubs. They are plant-parasites, with some species being significant agricultural pests, but due to their small size are often overlooked, and apart from a few species with major economic impact, are not well studied. The genus Caliothrips is apparently one of the best known Thrips groups, with twenty-two described species from across the tropics, however almost nothing is known about most of these species beyond brief descriptions made when they were named.

In a paper published in the journal Zootaxa on 12 July 2017, Laurence Mound of the Australian National Insect Collection, and Francisco Infante of El Colegio de la Frontera Sur describe a new species of Caliothrips from Chiapas State in southern Mexico.

The new species is named Caliothrips chiapas in reference to the state where it was discovered. The species is brown and yellow in colour with females reaching slightly over a millimetre in length, and the males a little smaller. The species was found living on the leaves of the Little Sunflower (Girasolillo), Tithonia tubiformis, but, significantly, not on its flowers, nor on any other species of plant found nearby. Interestingly the flowers were home to a range of other Thrips, none of which were found on the leaves. This suggests that Thrips are particular, not just in what plants they live upon, but in what plant of the plant they inhabit. Such information is recorded for very few species of Thrips, with many species, particularly in the tropics, known only from individuals obtained by beating plants to see what drops out. 

Caliothrips chiapas, host-plant and immatures. (1) Tithonia tubiformis. (2) Caliothrips chiapas larvae on leaf. (3) Caliothrips chiapas slide-mounted second instar larva. Mounde & Infante (2017).
Caliothrips chiapas was found growing on plants around the edge of a Pineapple field in the municipality of Frontera Hidalgo in Chiapas State, close to the border with Guatemala.

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Sunday, 23 July 2017

Three miners confirmed dead and one still missing after Earthquake-induced collapse at South African gold mine.

Three workers have been confirmed dead and one is still missing following an Earthquake-induced collapse at the Tau Lekoa Gold Mine at Orkney in North West Province on Saturday 22 July 2017. The incident was triggered by a Magnitude 0.8 Earthquake, while the men were 1350 m below the ground. Rescue workers are continuing to search for the missing man.

The location of the Tau Lekoa Gold Mine. Google Maps.

Earthquakes are rare in South Africa. Because of this rarity it is hard to make precise judgements about the cause of quakes in South Africa, due to a paucity of data. Northwestern South Africa is close the southern end of the Great Rift Valley exits the continent and passes out under the Indian Ocean. The Great Rift Valley is slowly splitting the African Plate in two allow a line from the Red Sea through Ethiopia, and which includes the great lakes and volcanoes of east-central Africa. This has the potential to open into a new ocean over the next few tens of millions of years, splitting Africa into two new, smaller, continents; Nubia to the west and Somalia to the east.

Movement on the African Rift Valley, with associated volcanoes. Rob Gamesby/Cool Geography.

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Sinkhole swallows car in El Paso, Texas.

A female driver had to be rescued after her car was swallowed by a sinkhole in El Paso, Texas, on Saturday 22 July 2017. The woman was manoeuvring in the vehicle when the road began to collapse beneath it. She exited the car and was pulled out of the hole by passers by with only minor injuries, with the subsidence continuing and dragging the vehicle some way further into the ground.

Sinkhole in El Paso, Texas, on 22 July 2017. KFOX 14.

Sinkholes are generally caused by water eroding soft limestone or unconsolidated deposits from beneath, causing a hole that works its way upwards and eventually opening spectacularly at the surface. Where there are unconsolidated deposits at the surface they can infill from the sides, apparently swallowing objects at the surface, including people, without trace.

 The approximate location of the 22 July 2017 El Paso sinkhole. Google Maps.

On this occasion the sinkhole was caused by the collapse of an overloaded storm drain beneath the road, releasing water that washed away soft sediments under the road. The incident happened amid heavy rains that caused several flash flooding incidents in the area. 

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Student killed by landslide at Himcchahari in Cox's Bazar District of Bangladesh.

A second year student at Dhaka University was killed and two others injured after a landslide close to a waterfall at Himchhari in the Cox's Bazar District of Chittagong, Bangladesh, on Saturday 22 July 2017. Sabbir Alam Ridwan was hit by a collapsing hillside at about 4.30 pm local time, and reportedly died instantly of head injuries. The two other students were treated for injuries in a local hospital. The incident happened after two days of heavy rain associated with the Asian summer monsoon. Landslides are a common problem after severe weather, 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.

Sabbir Alam Ridwan of Dhaka University, killed by a landslide at Himchhari in Cox's Bazar on 22 July 2017. The Daily Star.

Monsoons are tropical sea breezes triggered by heating of the land during the warmer part of the year (summer). Both the land and sea are warmed by the Sun, but the land has a lower ability to absorb heat, radiating it back so that the air above landmasses becomes significantly warmer than that over the sea, causing the air above the land to rise and drawing in water from over the sea; since this has also been warmed it carries a high evaporated water content, and brings with it heavy rainfall. In the tropical dry season the situation is reversed, as the air over the land cools more rapidly with the seasons, leading to warmer air over the sea, and thus breezes moving from the shore to the sea (where air is rising more rapidly) and a drying of the climate. This situation is particularly intense in South Asia, due to the presence of the Himalayas. High mountain ranges tend to force winds hitting them upwards, which amplifies the South Asian Summer Monsoon, with higher winds leading to more upward air movement, thus drawing in further air from the sea. 

Diagrammatic representation of wind and rainfall patterns in a tropical monsoon climate. Geosciences/University of Arizona.

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Magnitude 6.7 Earthquake between Kos and the Bodrum Peninsula kills two.

The United States Geological Survey reported a Magnitude 6.7 Earthquake at a depth of 10 km between the Greek island of Kos and the Bodrum Peninsula, Turkey, slightly after 1.30 am local time on Friday 21 July 2017 (slightly after 10.30 pm on Thursday 20 July, GMT). Two people have been reported dead on Kos following the event, both of whom have been identified as tourists, one being from Sweden and the other from Turkey, though they have not yet been named. About 430 people have been injured on Kos and Bodrum, with both having suffered extensive damage to buildings and infrastructure,and many tourists trapped in the area. A small tsunami was reported on Kos, and people have reported feeling the event as far away as Crete.

Damaged buildings on Kos following the 21 July 2017 Earthquake. Louisa Gouliamaki/Getty Images.

The island of Kos lies on the boundary between the Anatolian Plate, to the north, the Aegean Sea Plate (underlying the Peloponnese, Attica, The Cyclades Islands, Crete, the Dodecanese Islands and Turkey to the southeast of the Taurus Mountains) to the west and the African Plate to the south. Northern Greece and the north coast of Turkey lie on the Eurasian Plate. Both countries are highly prone to earthquakes because of this.

 The approximate location of the 21 July 2017 Kos Earthquake. USGS.

To the east the Arabian Plate  is being pushed north and west by the movement of the African Plate, further to the south. This leads to a zone of tectonic activity within the province, as the Arabian and Anatolian plates are pushed together, along the East Anatolian Fault, and past one-another, along the Dead Sea Transform.

 Damaged buildings on Kos following the 21 July 2017 Earthquake. Sky News.

This movement also leads to a zone of faulting along the northern part of Turkey, the North Anatolian Fault Zone, as the Anatolian Plate is pushed past the Eurasian Plate, which underlies the Black Sea and Crimean Peninsula  (transform faulting). This is not a simple process, as the two plates constantly stick together, then break apart as the pressure builds up, leading to Earthquakes, which can be some distance from the actual fault zone.

 Damage to boats at Bodrum following the 21 July 2017 Earthquake. Anadolu Agency.

The Aegean Sea Plate is moving southwest with regard to the Eurasian and Anatolian Plates, and being subducted beneath the African Plate to the south. Its margin with the Eurasian Plate is a divergent and a transform margin at different points. This is not a smooth process, with rocks tending to stick together, then being forced to move as the pressure builds up, typically in stops and starts that lead to Earthquakes.

 Simplified map of the plate movements of the eastern Mediterranean. Univeriteit Utrecht.

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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