Sunday, 15 December 2019

Magnitude 6.9 Earthquake in Davao del Sur Province, the Philippines.

The Philippine Institute of Volcanology and Seismology recorded a Magnitude 6.9 Earthquake at a depth of 3 km about 5 km to the west of the town of Matanao in Davao del Sur Province on Mindanao Island, Philippines, slightly after 2.10 pm local time (slightly after 6.10 am GMT) on Sunday 15 December 2019. The Earthquake is known to have killed at least four people, including a six-year-old girl, and injured many more, mostly in building collapses with the event being felt across the southern Philippines. 

 Vicitms of the 15 December 2019 Davao del Sur Earthquake, trapped beneath a wall in the town of Padada. Korte Supremo/Twitter.

The geology of the central Philippines is Complex. The west of Mindanao Island is located on the Banda (or Sunda) Microplate, and the east on the Philippine Plate, which is being subducted beneath the Sunda (or Banda) Microplate along the central part of the island. Immediately to the east of the Island the Pacific Plate is being subducted along the Philippine Trench, and passes beneath eastern Mindanao as it sinks into the Earth. This is not a smooth process, an the plates constantly stick together then break apart again as the pressure builds up, resulting in Earthquakes.

 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.

The location of the 15 December 2019 Davao del Sur Province Earthquake. Contour lines show rates of movement during the quake, the red line is a boundary between two tectonic plates, in this case the Pacific and Philippine plates. USGS.

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Saturday, 14 December 2019

Learthback Turtle found on beach in Essex, England.

A Leatherback Turtle, Dermochelys coriacea, has been discovered on a beach in Essex, southeast England, this week. The Turtle, which is estimated to weigh about 250 kg, was discovered by a Dog-walker on a beach on Mundon Creek, part of the Blackwater River Estuary System, on the morning of Wednesday 11 December 2019. The UK Cetacean Strandings Investigation Programme was called in to investigate the Turtle, and was able to work with the local Coastguard and landowners to recover the body of the animal, for examination at the Natural History Museum in London. Leatherback Turtles are occasionally washed up on the warmer beaches of southwest England and the south coast of Ireland, but have not previously been recorded on the east coast of England, or elsewhere on the North Sea.

The body of a Leatherback Turtle, Dermochelys coriacea, which was recovered on the Essex coast this week. South Woodham Coastguard Rescue Team.

Leatherback Turtles are the larges species of Chelonian (Turtles and Tortoises) alive today. and have a distinctive leathery shell which makes them easy to identify. They are placed in a separate family to all other Turtles, the Dermochelyidae, which has no other living species, but a fossil record dating back to the Late Cretaceous. Modern Leatherback Turtles are found in tropical and warm temperate waters in the Atlantic and Pacific Oceans, as well as in the southwest Indian Ocean. They are considered to be Vulnerable under the terms of the International Union for the Conservation of Nature's Red List of Threatened Species, mostly due to a loss of suitable breeding grounds due to Human encroachment; unlike other Turtle species their flesh is generally considered to oily for consumption by Humans, limiting the impact of hunting on the species, although they are vulnerable to being caught as bycatch in fishing nets and becoming entangled in abandoned fishing gear. Other marine plastics are also a significant risk to the species, as items such as plastic bags can resemble Jellyfish, the main diet of these Turtles.

Leatherback Turtle, Dermochelys coriacea, washed up on a beach in Essex, southeast England, earlier this week. Harwich and Manningtree Standard.

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The Geminid Meteor Shower.

The Geminid Meteor Shower is expected to peak at about 2.00 pm on Saturday 14 December this year (2019) with potentially up to 120 meteors per hour being visible in areas of the Northern Hemisphere with a clear sky. This year peak activity for the shower comes slightly after the Full Moon on Thursday 12 December, which may hamper viewing. The meteors appear to radiate from a point in the constellation of Gemini, hence their name.

The radiant point of the Gemenid Meteors (i.e. the point from which the meteors radiate). Gregg Dinderman/Sky & Telescope.
Oddly for a meteor shower, the Geminids do not appear to be related to a comet, but instead are associated with an object called 3200 Phaethon, which is classed as an Apollo Asteroid (an asteroid with an orbit that crosses that of the Earth). 3200 Phaethon has a highly elliptical orbit, which takes it in as close as 0.14 Au (14% of the distance between the Earth and the Sun, more than twice as close as Mercury) and out as far as 2.4 AU (2.4 times as far from the Sun as the Earth or 1.6 times as far as Mars). 3200 Phaethon does not appear to produce any sort of halo (a cloud of material produced by the evaporation of gas ice from the surface of a comet, thought to be the source of most meteor showers); rather it appears dark in colour an is classed as a B-type Carbonaceous Asteroid, thought to have a surface covering of  anhydrous silicates, hydrated clay minerals, organic polymers, magnetite, and sulphides.

Animation made from images of 3200 Phaeton captured on 17 December 2017, when it was at the closest point of its orbit to Earth, from the Arecibo Observatory in Puerto Rico. National Science Foundation/NASA/Wikimedia Commons.

Asteroid 3200 Phaethon is a 5 km body with a highly eccentric orbit similar to that of a comet, which takes it closer to the Sun than any other named Asteroid. It appears to be the parent body of the Geminid Meteors, which share essentially the same orbit as it, as well as a group of larger bodies known as the Phaethon-Geminid Complex. Such meteor showers typically form from the tail of a comet; as the comet approaches its perihelion (the closest point in its orbit to the Sun), ice at the surface sublimates away (turns directly from a solid to a gas - liquids do not form in a vacuum), releasing particles of silica trapped in the ice, which continue to follow essentially the same path as the comet, creating a meteor shower every time the Earth passes through this stream. However, 3200 Phaethon, which has a 1.43 year orbital period in which it reaches 0.14 AU from the Sun (14% of the distance between the Earth and the Sun, or less than half the distance at which Mercury orbits) is thought to regularly suffer surface temperatures in excess of 1000K, making it highly unlikely that it has ice on its surface, which calls its potential role as the parent body to the Geminid Meteors into question. 3200 Phaethon is classed as an Apollo Group Asteroid (an asteroid that is on average further from the Sun than the Earth, but which does get closer). As an asteroid probably larger than 150 m in diameter that occasionally comes within 0.05 AU of the Earth, it is also classified as a Potentially Hazardous Asteroid.

 The orbit and current position of 3200 Phaethon. The Sky Live 3D Solar System Simulator.

In a paper published on the arXiv online database at Cornell University Library on 17 June 2013, David Jewitt of the Department of Earth and Space Sciences and Department of Physics and Astronomy at the University of California Los AngelesJing Li of the Department of Earth and Space Sciences at the University of California Los Angeles, and Jessica Agarwal of the Max Planck Institute for Solar System Research, describe the results of a study of 3200 Phaeton using the NASA STEREO Spacecraft.

Jewitt et al. observed two successive perihelions of 3200 Phaeton, in June 2009 and May 2012. On both occasions they were able to observe a faint comet-like dust tail emerging from the body, even though it was apparently reaching temperatures that would rapidly destroy an icy comet. This tail grew rapidly, reaching a length of over 250 000 km within a day of first appearing, and appeared to represent material being lost from the parent body at a rate of about 3 kg per second.

Composite images of 3200 Phaethon in 2009 (top row) and 2012 (bottom row) compared with the projected sun- comet line (white). The Sun is to the upper right in each panel. Insets are 49000 square and show eld stars near to Phaethon to demonstrate the point spread function of the data. Each panel has North to the top, East to the left and shows the median of 30 images taken over a 1 day period. Jewitt et al. (2013).

Jewitt et al. suggest that at it's perihelion 3200 Phaethon is being heated to such a degree that hydrated minerals at its surface could be thermally fractured and desiccated, leading to the ejection of dust particles.

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Friday, 13 December 2019

Urechis caupo: Thousands of Fat Innkeeper Worms wash up on Point Reyes National Seashore. California.

Thousands of Fat Innkeeper Worms, Urechis caupo, have been found washed up on beaches in the Drakes Bay area of the Point Reyes National Seashore in northern California. The Worms, which are also known as 'Penis Fish', due to their somewhat distinctive appearance, appeared on he morning of Wednesday 11 December 2019, having apparently been scoured from burrows in the intertidal zone by a strong storm. This is a common phenomenon in the area during El Niño years, when packages of warm, wet air bring stormy conditions to the east coast of North America, but not other wise, with the effect that large numbers of Worms will appear on beaches mysteriously after several years of not being seen at all.

Thousands of Fat Innkeeper Worms, Urechis caupo, washed up on a beach in the Drake's Bay area of northern California this week. David Ford/Bay Nature.

Fat Innkeeper Worms, Urechis caupo, are a type of Spoon Worm, Echiura, a form of unsegmented marine Worm formerly thought to have been a separate phylum, but which have now been shown to be a type of Polychaete Annelid that have lost their segmentation. These Worms have a large fleshy proboscis which can be flattened into a scoop when burrowing, giving them the name 'Spoon Worms', and in the case of the large Fat Innkeeper, a rather phallic appearance.

A Fat Innkeeper Worm, Urechis caupo, found on a beach in the Bodega Bay  area of northern California in June 2019. Kate Montana/iNaturalist.

Most Spoon Worms are confined to deepwater environments, predominantly in the Atlantic Ocean. Only two species are known from the West Coast of North America, the Fat Innkeeper, and the smaller Listriolobus pelodes, which is found in deeper environments (18-155 m) off the coast of California and Baja California. The Fat Innkeeper is found in intertidal waters between Oregon and Baja California , and is an important part of the local ecology, excavating large, u-shaped burrows around a meter in length. which are shared by many other species, including the Clam, Cryptomya californica, the Sequined Scale-worm, Hesperonoe advento, the Pea Craba, Scleroplax granulata and Pinnixa franciscana, the Hooded Shrimp, Betaeus longidactylus, and the Arrow Goby, Clevelandia ios. It is the provision of large burrows shared with a community of other animals which gives the worm the common name Fat Innkeeper/ The Worms are also an important prey species for many other animals, including Sea Otters, Enhydra lutris, a wide range of Fish, Sharks, and Rays, and Humans.

The El Niño is the warm phase of a long-term climatic oscillation affecting the southern Pacific, which can influence the climate around the world. The onset of El Niño conditions is marked by a sharp rise in temperature and pressure over the southern Indian Ocean, which then moves eastward over the southern Pacific. This pulls rainfall with it, leading to higher rainfall over the Pacific and lower rainfall over South Asia. This reduced rainfall during the already hot and dry summer leads to soaring temperatures in southern Asia, followed by a rise in rainfall that often causes flooding in the Americas and sometimes Africa. Worryingly climatic predictions for the next century suggest that global warming could lead to more frequent and severe El Niño conditions, extreme weather conditions a common occurrence.

Predicted changes to North American weather patterns during an El Niño event. NWS/NCEP Climate Prediction Center/NOAA.

The relationship between storm conditions and inshore sedimentary environments is complicated, as such events can scour sediments from shallow environments and shift them into deeper ones, move large volumes of sediment from terrestrial environments to shallow marine ones, or simply move sediments from beach to beach. For smaller infaunal species with shorter life-spans, such changes are not a problem, but for long-lived species such as Fat Innkeepers, which can live for around 25 years, this is a major problem as it means fewer Worms live out their full life-cycle, and that each worm therefore produced fewer offspring during its life. Even if the Worms are able to maintain a population during such a crisis, with Worms producing enough larvae during their shorter lives to keep colonising new suitable sites as they appear, this would be a major problem for the species that share the Worms' burrows, as fewer Worms would reach their full potential size, leading to fewer, and smaller burrows being available.

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Thursday, 12 December 2019

Asteroid 2019 XM2 passes the Earth.

Asteroid 2019 XM2 passed by the Earth at a distance of about 879 900 km (2.29 times the average  distance between the Earth and the Moon, or 0.59% of the distance between the Earth and the Sun), slightly after 5.50 pm GMT on Thursday 5 December 2019. There was no danger of the asteroid hitting us, though were it to do so it would not have presented a significant threat. 2019 XM2 has an estimated equivalent diameter of 10-32 m (i.e. it is estimated that a spherical object with the same volume would be 10-32 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 31 and 15 km above the ground, with only fragmentary material reaching the Earth's surface.

 The calculated orbit of 2019 XM2. JPL Small Body Database.

2019 XM2 was discovered on 5 December 2019 (the day of closest encounter with the Earth) by the University of Tokyo's Kiso Observatory. The designation 2019 WM2 implies that the asteroid was the sixtieth object (asteroid D - 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 M2 = (24 x 2) + 12 = 60) discovered in the first half of December 2019 (period 2019 X).

2019 XM2 has a 479 day orbital period and an eccentric orbit tilted at an angle of 32.8° to the plane of the Solar System, which takes it from 0.96 AU from the Sun (i.e. 96% of he average distance at which the Earth orbits the Sun) to 1.43 AU from the Sun (i.e. 1.43% of the average distance at which the Earth 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 2019 XM2 occasionally comes close to the Earth, with  the last such lose encounter having happened in June this year (2019) and the next predicted for November 2023.
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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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