Aviation warning after eruption on Mount Bogoslof, Alaska.

The Alasaka Volcano Observatory issued a warning to aviation following an eruption on Bogoslof Island in the Aluetian Chain at about 2.15 pm local time on Sunday 28 May 2017. The eruption lasted for about 50 minutes, and produced an ash column which rose to between 10 000 and 12 000 m above the uninhabited island. 

Ash column over Mount Bogoslof on 28 May 2017. AP.

Bogoslof Island is uninhabited, and the islands around is are home to at most sparse Human populations, however it still presents a serious threat to air-traffic, as the Aleutian Islands lie in the path of a number of commercial aircraft routes, connecting the US to East Asia. Volcanic ash is extremely hazardous to aircraft in a number of ways. At its most obvious it is opaque, both visually and to radar. Then it is abrasive, ash particles physically scour aircraft, damaging components and frosting windows. However the ash is most dangerous when it is sucked into jet engines, here the high temperatures can melt the tiny silica particles, forming volcanic glass which then clogs engine. When this happens the only hope the aircraft has is to dive sharply, in the hope that cold air passing through the engine during the descent will cause the glass to shatter, allowing the engine to be restarted. Obviously this is a procedure that pilots try to avoid having to perform.

Bogoslof Island forms the tip of a submarine volcano that rises from the Bering Sea floor, 1.8 km below the surface. The island only rises 150 m above the surface, but is 1.76 km in length and 500 m wide, forming part of the rim of the caldera (crater) of the volcano; all eruptive activity occurs beneath the surface to the northeast of the island itself. The nature of the island means that it is frequently reshaped by eruptions.

 The approximate location of Bogoslof Island. Google Maps.

The volcanoes of the Alaskan Peninsula and Aleutian Islands are fed by magma rising from the Pacific Plate, which is being subducted beneath the North American Plate to the south along the Aleutian Trench. As the subducting plate sinks into the Earth it is subjected to enormous heat and pressure, causing more volatile minerals to melt. These then rise through the overlying North American plate as magma, fuelling the Alaskan volcanoes.

  How the subduction of the Pacific Plate beneath the North American Plate fuels the volcanoes of Alaska. Alaska Volcano Observatory.

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Asteroid 2017 KH5 passes the Earth.

Asteroid 2017 KH5 passed by the Earth at a distance of 509 200 km (1.32 times the average distance between the Earth and the Moon, 0.34% of the average distance between the Earth and the Sun), slightly before 4.25 pm GMT on Thursday 25 May 2017. There was no danger of the asteroid hitting us, though had it done so it would have presented no threat. 2017 KH5 has an estimated equivalent diameter of 5-19 m (i.e. it is estimated that a spherical object with the same volume would be 5-19 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 40 and 25 km above the ground, with only fragmentary material reaching the Earth's surface.

 The calculated orbit of 2017 KH5. Minor Planet Center.

2017 KH5 was discovered on 25 May 2017 (the day before 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 KH5 implies that the asteroid was the 133rd object (object H5) discovered in the second half of May 2017 (period 2017 K).

2017 KH5 has an 862 day orbital period and an eccentric orbit tilted at an angle of 7.85° to the plane of the Solar System, which takes it from 0.80 AU from the Sun (i.e. 80% of he average distance at which the Earth orbits the Sun) to 2.74 AU from the Sun (i.e. 274% of the average distance at which the Earth orbits the Sun, considerably over twice the distance at which the planet Mars orbits the Sun). 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 common, with the last having occurred in May 1981 and the next predicted for October 2064. 2017 KH5 also has occasional close encounters with the planet Mars, with the next predicted for September 2135. 

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Kidnapped mineworkers released in the Democratic Republic of Congo.

Four workers kidnapped from a mine in Maneima Province, Democratic Republic of Congo, on the first of March this year have been released following negotiations. The four men, three Congolese nationals and one from France, were kidnapped from the Namoya Gold Mine in Salamabila, along with a fifth man, from Tanzania, who was released a month ago.

The Namoya Gold Mine at Salamabila in Maneima Province, Democratic Republic of Congo. Banro Corporation.

Gold has been mined comercially at Namoya since the 1930s, in what was then the Belgian Congo., though production ceased in 1961 during the civil war that followed Congolese independence. The site was purchased from the Congolese Government by the Canadian mining giant Banro in 2013, with comercial production resuming in January 2016. However this has brought the company into conflict with local artisanal miners who had operated small scale mining on the site during the 50 years of inactivity, and who claim they were promised employment at the new mine inreturn for abandoning their activity, work which has not been forthcoming.

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Magnitude 5.0 Earthquake in Izmir Province, Turkey.

The United States Geological Survey recorded a Magnitude 5.0 Earthquake at a depth of 10 km, about 7 km to the west of the  town of Gölmarmara in Izmir Province, southwest Turkey, slightly after 6.50 pm local time (slightly after 3.50 pm GMT) on Saturday 27 May 2017. There are no reports of any fatalities associated with this event, but at least one person injured and a number of buildings destroyed. The event was felt across much of western Turkey. 

Damage following the 27 May 2017 Izmir Earthquake. Daily Sabah.

The majority of Asian Turkey lies on the Anatolian Plate, which is being pushed to the west by the northward movement of the Arabian Plate, which is in turn being pushed by the African Plate, further to the south. This creates as 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.

The approximate location of the 27 May 2017 Izmir Province Earthquake. USGS.

This northward movement of the African and Arabian Plates also causes folding and uplift in the Caucasus Mountains, which separate Georgia from Russia. Again this is not a smooth process, with the rocks sticking together, then moving sharply as the pressure builds up enough to break them appart, which can also lead to Earthquakes in the region.

Plate movements and fault zones around the Anatolian Plate. Mike Norton/Wikimedia Commons.

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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Garbage truck falls into sinkhole in Augusta, Georgia.

A garbage truck became trapped in a sinkhole in Augusta, Georgia, after a section of road collapsed beneath it at about 8.00 am local time on Thursday 25 May 2017. Nobody was hurt in the incident and the vehicle has subsequently been removed, but the section of road where it occurred is likely to remain closed for some time while engineers assess the situation and repairs are carried out.

The scene of the 25 May 2017 Augusta sinkhole. Doug Stutsman/The Augusta Chronicle.

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.

However on this occasion the sinkhole is believed to have been caused by a damaged sewer or storm drain, which leaded water that washed away soft sediments beneath the road until it collapsed. A number of houses in the area have been left without water following the event.  

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Asteroid 2017 KY4 passes the Earth.

Asteroid 2017 KY4 passed by the Earth at a distance of  948 300 km (2.47 times the average distance between the Earth and the Moon, 0.63% of the average distance between the Earth and the Sun), slightly before 3.50 pm GMT on Saturday 20 May 2017. There was no danger of the asteroid hitting us, though had it done so it would have presented no threat. 2017 KY4 has an estimated equivalent diameter of 22-68 m (i.e. it is estimated that a spherical object with the same volume would be 22-68 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 20 and 3 km above the ground, with only fragmentary material reaching the Earth's surface.

 

The calculated orbit of 2017 KY4. Minor Planet Center.

2017 KY4 was discovered on 22 May 2017 (two 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 KY4 implies that the asteroid was the 124th object (object Y4) discovered in the second half of May 2017 (period 2017 K).

2017 KY4 has an 406 day orbital period and an eccentric orbit tilted at an angle of 17.5° to the plane of the Solar System, which takes it from 1.002 AU from the Sun (i.e. 100.2% of he average distance at which the Earth orbits the Sun) to 1.15 AU from the Sun (i.e. 115% of the average distance at which the Earth orbits the Sun). It is therefore classed as an Amor Group Asteroid (an asteroid which comes close to the Earth, but which is always outside the Earth's orbit). This means that close encounters between the asteroid and Earth are fairly common, with the most recent having occurred in November 2007 next predicted in November this year.

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Sinkhole swallows car in Denver, Colorado.

A taxi was swallowed by a sinkhole in Denver, Colorado, in the early hours of Friday 26 May 2017, after the driver mistook the hole for a puddle caused by overnight rain, and drove into it. The driver was unhurt, and no passengers were in the vehicle at the time, but the taxi is thought likely to be written off after falling into the two meter hole.

Taxi trapped in a sinkhole in Denver, Colorado, on 26 May 2017. CBS News.

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.

However on this occasion the sinkhole is believed to have been caused by a burst water main, which washed away soft sediments beneath the road until it collapsed. A number of houses in the area have been left without water following the event.

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