Sunday, 24 May 2015

Asteroid 2015 KG passes the Earth.

Asteroid 2015 KG passed by the Earth at a distance of 5 510 000 km (14.3 times the average distance between the Earth and the Moon, or 3.68% of the average distance between the Earth and the Sun), slightly before 4.55 am GMT on Monday 18 May 2015. There was no danger of the asteroid hitting us, though had it done so it would have presented only a minor threat. 2015 KG has an estimated equivalent diameter of 7-24 m (i.e. it is estimated that a spherical object with the same volume would be 7-24  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 36 and 20 km above the ground, with only fragmentary material reaching the Earth's surface.

 The calculated orbit of 2015 KG. JPL Small Body Database.

2015 KG was discovered on 18 May 2015 (the day of 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 2015 KG implies that it was the seventh asteroid (asteroid G) discovered in the second half of May 2015 (period 2015 K). 

While 2015 KG occasionally comes near to the Earth, it does not actually cross our orbital path. It has an elliptical 856 day orbit, at an angle of 0.57° to the plane of the Solar System, that takes it from 1.04 AU from the Sun (1.04 times the average distance at which the Earth orbits the Sun), slightly outside our orbit, to 2.48 AU from the Sun, (2.48 times the distance at which the Earth orbits the Sun and considerably more than the distance at which the planet Mars orbits the Sun). As a Near Earth Object that remains strictly outside the orbit of the Earth it is classed as an Amor Family Asteroid. This means that 2015KG has regular close encounters with the Earth, with the last calculated to have occurred in April 2008 and the next predicted for June 2022. 2015 KG also has occasional close encounters with the planet Mars, with the most recent having occurred in July 1923.

See also...

Asteroid 2015 KM18 passed by the Earth at a distance of 8 760 000 km (22.8 times the average distance between the Earth and the Moon, or 5.86% of the average distance between the Earth and the Sun), slightly before 7.55 am GMT on Sunday 17 May...


Asteroid 2015 JD passed by the Earth at a distance of 1 366 000 km (3.55 times the average distance between the Earth and the Moon, or 9.13% of the average distance between the Earth and the Sun), at about 11.25 pm GMT on Sunday 10 May 2015. There was...


Asteroid 2015 JC1 passed by the Earth at a distance of 1 360 000 km (3.54 times the average distance between the Earth and the Moon, or 9.09% of the average distance between the Earth and the Sun), slightly after 5.50 pm GMT on Friday 8 May 2015. There was no...


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Eruptions on Piton de la Fournaise.

The Observatoire Volcanologique du Piton de la Fournaise reported a sharp rise in sulphur dioxide emissions from Piton de la Fournaise, a shield volcano which forms much of the eastern part of Réunion Island, an island in the western Indian Ocean which forms a department of France, on 3 May 2015, followed by a similar rise in hydrogen sulphide emissions on 5 May. From 4 May onwards a rise in Earthquake activity beneath the mountain, which often signifies magma moving through chambers beneath a volcano, was detected, combined with inflation of the base of the summit cone. This seismic activity climbed steadily till 17 May, when about 200 events were recorded over a period of about 90 minutes, between 11.00 am local time and 12.30 pm. A second burst of intense seismic activity began at about 12.50 pm, followed by an eruption from a new fissure to the southeast of Dolomieu Crater. A total of three new fissures were detected in the area that afternoon, all producing lava fountains, and tw lava flows were also observed, and a gas plume which rose about 4 km over the summit of the volcano and drifted to the northwest. The most westerly of the new fissures stopped emitting lava before midnight, and by morning on 18 may only a single fissure was active, producing a lava fountain reaching 40-50 m in height and a flow that travelled 4 km from the opening, as well as a smaller gas plume, with a high hydrogen sulphide and carbon dioxide content. On 19 May the fissure activity had subsided, with fountains reaching at most 20-30 m in height, and the lava flow proceeding only another 750 m during the day.

Lava fountain and flow emerging from a new fissure on Piton de la Fournaise. Clicanoo.

Piton de la Fournaise is believed to have been active for about 530 000 years, though its geology is complicated to unravel as lava flows are interbedded with those from Piton des Neiges, a larger, older and now extinct volcano to the northwest, which is responsible for the formation of about two thirds of the island. The island sits on the Réunion Hotspot, a deep mantle plume which is thought to have been active for about 66 million years, originally forming under what is now northeastern India, where it was responsible for the Deccan Traps flood basalts, then moving southward across the Indian Ocean (or more precisely sitting still while the continental plate upon which India and the Indian Ocean sit moves to the north), over time forming the Laccadive Islands, the Maldives, the Seychelles, Rodrigues Island, Mauritius and Réunion.

The location of Piton de la Fornaise on Réunion Island.  Google Maps.

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On Wednesday 4 February 2014 the Observatoire Volcanologique du Piton de la Fournaise recorded 180 Earthquakes between 4.00 and 9.00 am, on Piton de la Fournaise, a shield volcano which forms much of...


A report in the Times of India on 6 June 2014 has documented a possible volcanic eruption in the Kangra District of Himachal Pradesh State, India. The...


The Volcanic Observatory of Goma have issued a warning of a possible impending eruption on Mount Nyamulagira, an active volcano close to Mount Nyiragongo in the Virungu Mountains of eastern Democratic Republic of Congo, about 25 km to the north of Lake Kivu. Mount Nyamalugira is often considered...


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Magnitude 4.1 Earthquake in Napa County, California.

The United States Geological Survey recorded a Magnitude 4.1 Earthquake at a depth of about 13 km about 6 km to the east of Yountville in Napa County, California, slightly after 7.50 pm local time on Thursday 21 May 2015 (slightly after 2.50 am on Friday 22 May, GMT). There are no reports if any damage or injuries associated with this event, though it was felt across much of Napa and Sonoma counties.

The approximate location of the 22 May 2015 Napa County Earthquake. Google Maps.

California is extremely prone to Earthquakes due to the presence of the San Andreas Fault, a tectonic plate margin that effectively bisects the state. The west of California, including Santa Barbara and Los Angeles, is located on the Pacific Plate, and is moving to the northwest. The east of California, including Fresno and Bakersfield is on the North American Plate, and is moving to the southeast. The plates do not move smoothly past one-another, but constantly stick together then break apart as the pressure builds up. This has led to a network of smaller faults that criss-cross the state, so that Earthquakes can effectively occur anywhere.

The extent of and movement on the San Andreas Fault. Geology.

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The United States Geological Survey recorded a Magnitude 3.6 Earthquake to the north of San Ramon in Contra Costa County, California, slightly after...


A woman has died and her male companion has been severely injured following a cliff collapse at the Point Reyes National Seashore to the northwest of San...



The United States Geological Survey recorded a Magnitude 6.0 Earthquake at a depth of 11.3 km in southern Napa County, California, at about 3.20 am local time (bout 10.20 am GMT) on Sunday 24...


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Saturday, 23 May 2015

Giant sinkholes appear at Missouri golf course.

A pair of giant sinkholes have appeared at the Top of the Rock Golf Course in Taney County, Missouri, on Friday 22 May 2014. The larger of the two sinkholes measures 25 m across by 10 m deep, while the smaller is 8 m wide and 6 m deep. Nobody has been hurt by the appearance of the holes, but they have caused considerable damage to the course, which regularly hosts major tournaments.

One of the sinkholes at the Top of the Rock Golf Course on Friday 22 May 2015. NWA.

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.

Such sinkholes are quite common in the Top of the Rock area, which lies on karstic limestone (limestone in the process of being eroded away by water percolating through it); the golf course is actually part of a large leisure and tourism complex built around a system of limestone caves in the Ozark Mountains. The sinkholes are currently being investigated by geologists who believe they may be connected to a previously unknown cave or cave system.

The location of the Top of the Rock Golf Course. Google Maps.

See also...

Magnitude 3.6 Earthquake in Pemiscot County, southeast Missouri.
The United States Geological Survey recorded a Magnitude 3.6 Earthquake at a depth of 10 km, roughly 3 km to the south of the city of Steele in...

The United States Geological Survey recorded a Magnitude 2.8 Earthquake at a depth of 7.7 km, roughly 4 km to the west of the city of Malden in Dunklin...


Two workers have been killed at a lime mine in Ste Genevieve, Missouri, on Friday 11 April 2014. John Hahl (54) and Chris Rawson (29) were working in a suspended basket at the mine, collecting loose material from a rockface, when the basket was struck by a falling rock, detaching it and causing the men to fall...


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Asteroid 2015 KM18 passes the Earth.

Asteroid 2015 KM18 passed by the Earth at a distance of 8 760 000 km (22.8 times the average distance between the Earth and the Moon, or 5.86% of the average distance between the Earth and the Sun), slightly before 7.55 am GMT on Sunday 17 May 2015. There was no danger of the asteroid hitting us, though had it done so it would have presented only a minor threat. 2015 KM18 has an estimated equivalent diameter of 24-75 m (i.e. it is estimated that a spherical object with the same volume would be 24-75 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 2 km above the ground, with only fragmentary material reaching the Earth's surface, although since an object at the upper end of this range would be expected to release an amount of energy equivalent to about 20 megatons of TNT (roughly 1200 times the energy released by the Hiroshima bomb), then being directly underneath it might be fairly unpleasant.

 The calculated orbit of 2015 KM18. JPL Small Body Database.

2015 KM18 was discovered on 19 May 2015 (two days after its closest approach to the Earth) by the University of Arizona's Catalina Sky Survey, which is located in the Catalina Mountains north of Tucson. The designation 2015 KM18 implies that it was the 462nd asteroid (asteroid M18) discovered in the second half of May 2015 (period 2015 K).

While 2015 KM18 occasionally comes near to the Earth, it does not actually cross our orbital path. It has an elliptical 635 day orbit, at an angle of 18.0° to the plane of the Solar System, that takes it from 1.08 AU from the Sun (1.06 times the average distance at which the Earth orbits the Sun), slightly outside our orbit, to 1.83 AU from the Sun, (1.83 times the distance at which the Earth orbits the Sun and considerably more than the distance at which the planet Mars orbits the Sun). As a Near Earth Object that remains strictly outside the orbit of the Earth it is classed as an Amor Family Asteroid.

See also...

Asteroid 2015 JD passed by the Earth at a distance of 1 366 000 km (3.55 times the average distance between the Earth and the Moon, or 9.13% of the average distance between the Earth and the Sun), at about 11.25 pm GMT on Sunday 10 May 2015. There was...


Asteroid 2015 JC1 passed by the Earth at a distance of 1 360 000 km (3.54 times the average distance between the Earth and the Moon, or 9.09% of the average distance between the Earth and the Sun), slightly after 5.50 pm GMT on Friday 8 May 2015. There was no...


Asteroid 2015 HQ171 passed by the Earth at a distance of 446 400 km (1.16 times the average distance between the Earth and the Moon, or 2.98% of the average distance between the Earth and the Sun), slightly after 3.50 am GMT on Saturday 2 May 2015. There was no danger of the asteroid hitting us...



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Volcanic activity on Mount Etna.

The Osservatorio Etneo at the Istituto Nazionale di Geofisica e Vulcanologia reported the beggining of a new phase of volcanic activity on Mount Etna, an active volcano on the island of Sicily beginning on Tuesday 12 May 2015 with a series of Earth tremors beneath the mountain. At about 4.10 am local time on Wednesday 13 May an east-west fracture appeared beneath the east rim of the volcano's New Southeast Crater, revealing a series of vents, one of which produced a small lava flow. At about 8.00 am the fracture began to spead again, reaching about 200 m from the rim of the cone in under 10 minutes. This was accompanied by further rim collapses and the ejection of a quantity of incandescent ash around the summit of the volcano and down its southern flank.This activity continued till 16 May, though it began to die of on the 15th. Further small lava eruptions ashfalls occured around the south and northeast of the volcano; a lava flow was reported which trended northeast then split in two flowing to the west and east, the western flow reaching 5 km from the vent.

 Flow of lava issuing from Mount Etna on 16 May 2015. Marco Restivo/Barcroft Media.

Etna first erupted about half a million years ago, beneath the sea off the east coast of Sicily, and has been going strong ever since. It now stands 3330 m above sea level, and covers 1200 km³. It is responsible for fertile soils across eastern Sicily. Records of eruptions on Etna go back to 1500 BC. It is Europe's second largest volcano, after Teide in the Canary Islands, and is one of the most active volcanoes in the world.

 The location of Mount Etna. Google Maps.

Despite all this Etna has only ever caused 77 recorded deaths (the most recent being two tourists caught in a summit explosion in 1987) and relatively little destruction. In 1928 it destroyed the village of Mascali on its northeastern flank, though there were no reported casualties, the village being slowly overrun by a lava flow. In 1669 a much larger lava flow destroyed at least 10 villages, reaching the walls of the city of Catania, 40 km to the south, but again without loss of life. In 122 BC a heavy ash fall covered much of the region, causing several buildings to collapse in Catania. The destruction was deemed so severe by the Roman authorities that they granted the city a 10 year tax holiday. In about 6000 BC a landslide on the eastern flank of the volcano is thought to have caused a tsunami that caused destruction around much of the eastern Mediterranean.

Etna is located on the border of the African and European Plates, specifically where Africa is being subducted beneath the European Plate. As it is drawn into the Earth's interior material from the African Plate melts, and the lighter portions rise up through the overlying European Plate, causing a number of volcanoes including Etna and Vesuvius.
 
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Mount Etna, Europe's most active volcano, located on the east of the island of Sicily, underwent a series of large eruptions overnight on Saturday 16-Sunday 17 November 2013, throwing lava and iridescent rocks...
 
Mount Etna, a 3320 m active stratovolcano on eastern Sicily, erupted on Saturday 26 October 2013, producing an ash column which briefly closed airspace over the island and and throwing hot ash and lava out of its crater. This follows a series of small...
 
On the 4th of July 2011 loud explosions were heard from a pit crater on the eastern flank of Mount Etna's southeastern cone (Etna has four cones, the southeast cone in the newest having only formed in 1978). That evening the cone was seen to be glowing, and over...
 
 
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Friday, 22 May 2015

Magnitude 4.2 Earthquake off the coast of Sandwich Bay, Kent.

The British Geological Survey recorded a Magnitude 4.2 Earthquake at a depth of 13 km off the coast of Sandwich Bay, Kent, in the southeast of England slightly after 2.50 am British Summertime (slightly after 1.50 am GMT) on Monday 11 May 2015. There are no reports of any injuries associated with this event, though there are unconfirmed reports of houses being damaged in the village off Flete, to the north of the epicenter of the quake, and people have reported feeling the event across all of Kent and as far away as Oxfordshire and Norfolk.

Map showing the epicenter of the 22 May 2015 East Kent Earthquake, and the areas where it was felt. BGS.

Earthquakes become more common as you travel north and west in Great Britain, with the west coast of Scotland being the most quake-prone part of the island and the northwest of Wales being more prone  to quakes than the rest of Wales or most of England. However, while quakes in southern England are less frequent, they are often larger than events in the north, as tectonic presures tend to build up for longer periods of time between events, so that when they occur more pressure is released.


The precise cause of Earthquakes in the UK can be hard to determine; the country is not close to any obvious single cause of such activity such as a plate margin, but is subject to tectonic pressures from several different sources, with most quakes probably being the result of the interplay between these forces.

Britain is being pushed to the east by the expansion of the Atlantic Ocean and to the north by the impact of Africa into Europe from the south. It is also affected by lesser areas of tectonic spreading beneath the North Sea, Rhine Valley and Bay of Biscay. Finally the country is subject to glacial rebound; until about 10 000 years ago much of the north of the country was covered by a thick layer of glacial ice (this is believed to have been thickest on the west coast of Scotland), pushing the rocks of the British lithosphere down into the underlying mantle. This ice is now gone, and the rocks are springing (slowly) back into their original position, causing the occasional Earthquake in the process.

(Top) Simplified diagram showing principle of glacial rebound. Wikipedia. (Bottom) Map showing the rate of glacial rebound in various parts of the UK. Note that some parts of England and Wales show negative values, these areas are being pushed down slightly by uplift in Scotland, as the entire landmass is quite rigid and acts a bit like a see-saw. Climate North East.

Witness accounts of Earthquakes can help geologists to understand these events, and the structures that cause them. If you felt this quake, or were in the area but did not (which is also useful information) then you can report it to the British Geological Survey here.

See also...

The British Geological Survey recorded a Magnitude 1.9 Earthquake at a depth of 6 km slightly to the northeast of the village of North Fambridge in Essex...

Homes evacuated after sinkhole opens up in Swanley, southeast England.
Two homes have been evacuated in the town of Swanley in Kent, southeast England after a sinkhole opened up on Thursday 26 March 2015 swallowing...

Second Hampshire Earthquake in three days.
The British Geological Survey recorded a Magnitude 1.8 Earthquake at a depth of 4 km, roughly 3 km to the northeast of Winchester in Hampshire, England, at about 4.25 pm GMT on...


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