Tuesday, 10 December 2019

Indonesian authoriteis arrest five suspected Tiger poachers in Riau Province, Sumatra.

Five people have been arrested on suspicion of Tiger poaching in the Pelalawan Regency of Riau Province, Sumatra on Saturday 7 December 2019. Three people were initially arrested in a raid in Teluk Binjai village by personnel from the Environment and Forestry Ministry and the National Police, following a tip off they were trying to sell a Tiger skin. The three were found to be in possession of both the skin of a female Tiger, and a jar containing four Tiger foetuses; it is not clear if they come from the same animal. The three gave the names of two further people who were later arrested in Pangkalan Lesung subdistrict. It is thought that all of these individuals were part of a ring of poachers and smugglers that had targeted Tigers on several parts of the island of Sumatra.

Tiger body parts seized in a raid by authorities in Sumatra this week. AFP.

The Sumatran Tiger, Panthera tigris sondaica, is considered to be Critically Endangered under the terms of the International Union for the Conservation of Nature's Red List of Threatened Species, with less than 400 individuals surviving on the island of Sumatra; the subspecies was formerly also found on Java and Borneo, but is thought to be extinct there. Sumatran Tigers are threatened by habitat loos and poaching, with poaching thought to be resulting in the loss of about 40 animals per year.

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Monday, 9 December 2019

One person dead and up to twenty seven missing following eruption on White Island, New Zealand.

One person is known to have died and twenty seven more are missing, following an eruption on White Island, or Te Puia o Whakaari, an island volcano in New Zealand's Bay of Plenty, 48 km from the mainland of North Island. The island is uninhabited, but was being visited by several groups of tourists at the time of the eruption, with the largest group coming from the cruise ship Ovation of the Seas. The exact number of people on the island at the time of the eruption is unclear, but it is thought to have been less than 50, with 23 people having been evacuated by tour operators, seven of whom are described as being in a serious condition. The island is currently thought to be too dangerous for emergency services to approach,  and it is unclear if there are likely to be any more survivors. The eruption occurred slightly after 2.10 pm local time (slightly after 1.10 am GMT) on Monday 9 December 2019, producing an ash column that rose 4 km above the island.

Eruption on White Island, New Zealand, on 9 December 2019. Michael Schade/The Guardian.

White Island is the tip of a submerged stratovolcano (cone-shaped volcano made up of successive layers of ash and lava), reaching 321 m above sea-level and measuring 2 × 2.4 km. The volcano is highly active, having erupted numerous times since written records began in 1826, and with more eruptions mentioned in Maori oral traditions (the name Te Puia o Whakaari means 'The Dramatic Volcano'. The island is uninhabited, due to its small size and the presence of an active volcano (an attempt to mine sulphur on the island ended in disaster in 1914, when an eruption triggered a lahar - sudden flow of water, mud and ash - that killed all ten miners).

The approximate location of White Island. Google Maps.

The volcanoes of New Zealand are fed by the subduction of the Pacific Plate beneath the Islands, which sit on the eastern margins of the Australian Plate. As the Pacific Plate sinks into the Earth, a combination of heat from the friction and from the planet's interior partially melts the plate, and some of the melted material rises through the overlying Australian Plate, supplying the volcanoes of New Zealand with liquid magma.

 The subduction zone beneath New Zealand, and how if fuels Earthquakes and volcanos. Te Ara.

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Sunday, 8 December 2019

Magnitude 5.2 Earthquake off the coast of Costa Rica.

The United States Geological Survey recorded a Magnitude 5.2 Earthquake at a depth of 10 km,  roughly 10 km off the west coast of the Peninsula de Nicoya in Guanacaste Province on the Pacific Coast of Costa Rica, slightly after 12.30 pm local time  (slightly after 6.30 pm GMT) on Sunday 8 December 2019. There are no reports of any damage or casualties associated with this event, but it was felt across much of western Costa Rica.
The approximate location of the 8 December 2019 Costa Rica Earthquake. USGS.
Costa Rica lies on the southern margin of the Caribbean Plate; to the south of the country the Cocos Plate, which underlies part of the eastern Pacific Ocean) is being subducted under the Middle American Trench, passing under Central America as it sinks into the Earth's interior. This is not a smooth process, and the plates often stick together until the pressure builds up enough to force them to shift suddenly, causing Earthquakes. As the Cocos Plate sinks deeper if is partially melted by the friction and the heat of the Earth's interior. Some of the melted material then rises up through the overlying Caribbean Plate, fuelling the volcanoes of Central America.
 Diagram showing the passage of the Cocos Plate beneath Costa Rica (not to scale). Carleton College.
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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Flooding and landslides kill at least sixteen in Western Uganda.

At least sixteen people have died in a series of flooding and landslide events in the Bundibugyo District of Western Uganda this weekend, according to the Uganda Red Cross. The incidents happened after weeks of heavy rains left soil in many parts of the area waterlogged, so that when the rains intensified on Saturday 7 December 2019, the ground was unable to soak up the water, causing it to accumulate on the surface and leading to a series of flash floods and landslides. 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. Several more people are still missing in the area, with rescuers still searching the landslide sites for more bodies.

Flooding in Bundibugyo District, this weekend. Uganda Red Cross.

The incidents occurred after about a month of heavy rains, in one of the area's two annual rainy seasons. This two rainy seasons per year pattern is typical in equatorial countries, with rainy seasons around the equinoxes and dry seasons around the solstices. Upland areas of East Africa have always been prone to landslides, but the problem has become worse in recent years as a rising population has led to more agriculture on hill-slopes, in many areas replacing open woodland where tree roots served to stabilise slopes, and also to more people living in harms ways. This years rains have been exceptionally heavy, and fatalities due to similar events have also been reported in other parts of Kenya, Somalia, Ethiopian, South Sudan, Sudan, Tanzania, the Democratic Republic of Congo, the Republic of Congo, Burundi and the Central African Republic.

The rains this year are thought to have been made worse by the development of a meteorological phenomenon called a Negative Indian Ocean Dipole. Indian Ocean Dipole Phases are similar to the El Niño/La Niña climatic oscillation that affect the Pacific Ocean. Under normal circumstances equatorial waters off the east coast of Africa and west coast of Indonesia are roughly similar in temperature, however during a Negative Indian Ocean Dipole Phase the waters off the coast of Indonesia become significantly warmer. As the prevailing currents in the area flow west to east, this warm water is then pushed onto the shallower continental shelf of north Australia, where it warms the air over the sea more rapidly, leading to increased evaporation (which fuels rain) and a drop in air pressure over the east Indian Ocean and west Pacific. This in turn drives air currents over the Indian Ocean to flow more strongly west to east, leading to higher rates of  cooling off the coast of Africa (where more water is drawn up from the cool sea depths) and more warming off the coast of Indonesia, fuelling a feedback cycle that tends to remain through the winter season in any year when it forms. This leads to a particularly wet winter across much of Australia, as well as a potentially damaging heatwave in the north, while much of East Africa is at risk of drought (during a Positive Indian Ocean Dipole Phase the reverse happens, with drought in Australia and flooding in East Africa).

 Areas of warming and cooling and air flow during a Negative Indian Ocean Dipole Phase. Australian Bureau of Meteorology.

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Asteroid 2016 AF193 passes the Earth.

Asteroid 2016 AF193 passed by the Earth at a distance of about 15 977 000 km (41.6 times the average distance between the Earth and the Moon, or 10.7% of the distance between the Earth and the Sun), slightly after 9.35 am GMT on Monday 2 December 2019. There was no danger of the asteroid hitting us, though were it to do so it would have presented a significant threat. 2016 AF193 has an estimated equivalent diameter of 78-250 m (i.e. it is estimated that a spherical object with the same volume would be 78-250 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 4000 times as powerful as the Hiroshima bomb. Such an impact would result in an impact crater over 4 km in diameter and devastation on a global scale, as well as climatic effects that would last years or even decades.

The calculated orbit and current position of 2016 AF193. JPL Small Body Database Browser.

2016 AF193 was discovered on 14 January 2019 by the University of Hawaii's PANSTARRS telescope. The designation 2016 AF193 implies that it was the 4638th asteroid (asteroid F193 - in numbering asteroids the letters A-Y, excluding I, are assigned numbers from 1 to 24, with a number added to the end each time the alphabet is ended, so that A = 1, A1 = 25, A2 = 49, etc., which means that F193 = 6 + (24 X 193) = 4638) discovered in the first half of January 2016 (period 2016 A).
2016 AF193 has a 299 day orbital period, with an elliptical orbit tilted at an angle of 6.45° to the plain of the Solar System which takes in to 0.61 AU from the Sun (61% of the distance at which the Earth orbits the Sun, and less than the distance at which Venus orbits the Sun) and out to 1.13 AU (13% 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 February 2016 and the next predicted in June next year (2020). The asteroid also has frequent close encounters with the planet Venus, with the last though to have happened in March last year (2018) and the next predicted for August next year (2020). Although it does cross the Earth's orbit and is briefly further from the Sun on each cycle, 2016 AF193 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, 2016 AF193 is also classified as a Potentially Hazardous Asteroid.
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