Wednesday, 24 April 2019

Magnitude 5.9 Earthquake in Arunachal Pradesh, India.

The United States Geological Survey recorded a Magnitude 5.9 Earthquake at a depth of 14 km about 33 km to the north of the town of Aalo in West Siang District, Arunachal Pradesh, India, at about 1.45 am local time on Wednesday 24 April 2019 (about 8.15 pm on Tuesday 23 April GMT); the same Earthquake was measured by the China Seismological Network as a Magnitude 6.3 event at a depth of 10 km in Medong County, Tibet, which occured at a 4.15 am local time (this difference is caused by China and India both having a single standard time zone, with the effect that the focal points detected by the two agencies, while only a few km apart, are in time zones with a difference of three hours). The event was felt across northeastern India, as well as in China, Myanmar, Bangladesh, Bhutan, and Nepal, though there are no reports of any damage or casualties. 

The approximate location of the 6 December 2017 Tibet Earthquake. USGS.

Earthquake activity in the area is caused by the uplift of the Tibetan Plateau, due to the impact of India into Eurasia to the south. he Indian Plate is moving northwards at a rate of 5 cm per year, causing it to impact into Eurasia, which is also moving northward, but only at a rate of 2 cm per year. The collision of the Indian and Eurasian plates has lead to the formation of the Himalayan Mountains, the Tibetan Plateau, and the mountains of southwest China, Central Asia and the Hindu Kush.

 Block diagram showing how the impact of the Indian Plate into Eurasia is causing uplift on the Tibetan Plateau. Jayne Doucette/Woods Hole Oceanographic Institution.

Much of northern India and neighbouring areas of Central Asia and the Himalayas, are prone to Earthquakes caused by the impact of the Indian Plate into Eurasia from the south. When two tectonic plates collide in this way and one or both are oceanic then one will be subducted beneath the other (if one of the plates is continental then the other will be subducted), but if both plates are continental then subduction will not fully occur, but instead the plates will crumple, leading to folding and uplift (and quite a lot of Earthquakes). The collision of the Indian and Eurasian plates has lead to the formation of the Himalayan Mountains, the Tibetan Plateau, and the mountains of southwest China, Central Asia and the Hindu Kush.

 The movement of India into Eurasia over the last 71 million years. USGS.

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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Mudslide at Myanmar jade mine kills fifty seven.

Fifty seven workers are believed to have died following a mudslide at a jade mine in Kachin State, Myanmar on Monday 22 April 2019.  The incident happened close to the village of Maw Wun Kalay near Hpakant in Mohniyn District at about 11.30 pm local time, when part of a retaining wall around a filtration pond (pond in which soft sediments are washed in order to extract gemstones) collapsed, sending a surge of liquid mud and waste through a living quarters used by workers from two companies operating in the area, Myanmar Thura Gems and Shwe Nagar Koe Kaung. It is thought to be highly unlikely there will be any survivors.

Rescue workers at the scene of a mudslide that engulfed the living quarters of 57 workers near Maw Wan Kaley in Kachin State, Myanmar, this week. Myanmar Fire Services Department.

Myanmar is the world's largest producer of jade, though much of this is produced (along with other precious and semi-precious minerals such as amber) at unregulated (and often illegal) artisanal mines in the north of the country, from where it is smuggled into neighbouring China. Accidents at such mines are extremely common, due to the more-or-less total absence of any safety precautions at the site. At many sites this is made worse by the unregulated use of explosives to break up rocks, often leading to the weakening of rock faces, which can then collapse without warning. The majority of people in this industry are migrant workers from the surrounding countryside, not registered with any local authority, which can make it difficult for rescuers to identify victims following such events, or even gain accurate assessments of the number of people likely to have been involved in such accidents.

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Moros intrepidus: A small Tyrannosauroid Theropod from the early Late Cretaceous of Utah.

Tyrannosauroids were the top predators in latest Cretaceous ecosystems in Asia and North America, reaching sizes of up to nine metres and having adaptive features such as rapid growth, specialised bone-crushing jaws and apparently well-developed senses of smell and vision. However, their time as top predators appears to have been limited to the last 15 million years of the Cretaceous, with the group having a much longer history as smaller predators, first appearing in the Middle Jurassic but being overshadowed by larger groups such as the Allosaurs. How the Tyrannosauroids made this transition from small to large predators is difficult to understand, particularly as the transition appears to have happened in North America, where there is a long gap in the Tyrannosauroid fossil record, between the small species of the Jurassic and Early Cretaceous, and the large species that appeared at the End Cretaceous. 

In a paper published in the journal Communications Biology on 21 February 2019, Lindsay Zanno of Paleontology at the North Carolina Museum of Natural Sciences, the Department of Biological Sciences at North Carolina State University, and the Section of Earth Sciences at the Field Museum of Natural History, Ryan Tucker of the Department of Earth Sciences at Stellenbosch University, Aurore Canoville, Haviv Avrahami, and Terry Gates, also of Paleontology at the North Carolina Museum of Natural Sciences and the Department of Biological Sciences at North Carolina State University, and Peter Makovicky, also of the Section of Earth Sciences at the Field Museum of Natural History, describe a new species of small Tyrannosauroid from the earliest Late Cretaceous Cedar Mountains Formation of Utah. 

The new species is named Moros intrepidus, where ‘Moros’ means ‘impending doom’ and ‘intrepidus’ means ‘intrepid’. The species is described from a partial right hindlimb, comprising portions of the femur, tibia, fourth, and second metatarsals and phalanges of the fourth digit, excavated from the ‘Stormy Theropod’ exposure of the Cedar Mountains Formation in Emery County, Utah, the precise location of which is restricted by Utah state statute. Analysis of zircons from the same horizon suggests that the specimen is no more than 96.4 million years old. 

Right femur of Moros intrepidus. (a) Lateral, (b) cranial, (c) medial, (d) caudal, (e) proximal, and (f) distal views. Partial mid-diaphyseal cross-section of the femur shown in (g) polarized light with lambda filter, (h) natural light with numbered arrows and tracings indicating seven growth cycles, and (i) polarized light. Abbreviations: ar adductor ridge, at accessory trochanter, Ca caudal aspect, Cr cranial aspect, ft fourth trochanter, if intercondylar fossa, inf intertrochanteric nutrient foramen, L lateral aspect, L2 lobe on lesser trochanter, lic linea intermuscularis caudalis. lt lesser trochanter, M medial aspect, mdc mesiodistal crest, pf popliteal fossa, pld lateral depression, proximal. pnf principle nutrient foramen, sat semicircular accessory tuberosity, ts trochanteric shelf. Scale bars (a)–(e) 5 cm; (g)–(i) 1mm. Zanno et al. (2019). 

As well as the hindlimb, Zanno et al. describe two isolated premaxillary teeth from separate exposures of the Cedar Mountains Formation at Suicide Hill and the Cliffs of Insanity. These are flattened in aspect with one concave edge, interpreted as the inner surface, and distinct carinae (grooves) on their front and back surfaces, all features typical of Tyrannosauroids. 

 (c) Silhouette of Moros intrepidus showing recovered elements. Isolated indet. tyrannosauroid premaxillary tooth recovered from nearby strata in (d) occlusal, (e) mesiodistal, and (f) lingual views. Holotype specimen of Moros intrepidus composed of (g) femur, (h) tibia, (i) fourth metatarsal, (j) second metatarsal, and (k) pedal phalanges of the fourth digit. Scale bar (c) 1 m, (g)–(k) 5 mm. (d)–(f) Enlarged to show detail, not to scale. Zanno et al. (2019). 

Based upon the size of the known bones, Moros intrepidus is estimated to have had a mass of about 78 kg. Examination of the microstructure of the bones of the specimen suggests that it was at least six-to-seven years old when it died (Tyrannosauroids are known to have had seasonal growth, resulting in bands of denser material within their bones that form growth rings similar to those seen in trees; because bone is sometimes re-absorbed by the body during growth, this cannot provide as an absolute age, but counting the rings does give a rough minimum age for a specimen). This implies a growth rate similar to that seen in Jurassic Asian Tyrannosauroids such as Guanlong wucaii, a specimen of which with a similar size to Moros intrepidus has been estimated to have been about seven years old when it died, and is in marked contrast to later North American Tyrannosaurids such as Gorgosaurus ibratus, which would have been around three times as large at a similar age. This suggests that the emergence of large Tyrannosauroids really was restricted to the last few million years of the Cretaceous, and may have been closely linked to the disappearance of the earlier large Allosaurs.

Phylogenetic relationships, chronostratigraphic, and palaeoecological implications of Moros intrepidus. (a) Graphic illustrating temporal range of North American Tyrannosauroids including species-level range prior to the discovery of Moros intrepidus, extension of current range, and hypothesized range based on isolated teeth. The current gap in the North American Tyrannosauroid record spans from the Tithonian to the Aptian. Faunal composition of Late Cretaceous ecosystems was established between the Albian and Turonian, as recognized by the stratigraphic appearance of major clades. (b) generalized phylogenetic relationships of Tyrannosauroidea, showing the appearance of select traits related to cursoriality in Tyrannosaurs that are newly optimized as a result of the discovery of Moros intrepidus. (c) Stratigraphic distribution of Allosauria in North America (including Megaraptora) documents overlap with Moros intrepidus in early Late Cretaceous ecosystems leading to (d) refined calibration on the origin of late diverging Tyrannosauroids and clade-level faunal turnover within apex predator roles throughout the Late Jurassic–Late Cretaceous of North America. Coloured polygons are stylized call-outs and are not intended to reflect two dimensional data. Zanno et al. (2019). 

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Monday, 22 April 2019

Magnitude 6.1 Earthquake beneath Luzon Island kills at least eight.

The United States Geological Survey recorded a Magnitude 6.1 Earthquake at a depth of 20 km beneath central Luzon Island, the Philippines, slightly after 5.10 pm local time (slightly after 9.10 am GMT) on Monday 22 April 2019. The event is reported to have caused at least eight fatalities, with five people, including two children, killed in separate house collapses in the towns of Porac and Lubao Pampanga Province, and three more known to have died in a supermarket collapse in Porac, where about forty more are feared to be beneath the remains of the building (though some have been extracted alive).

Water from a roof-top swiming pool cascading down the side of the Anchor Skysuites building in Manila following a Magnitude 6.1 Earthquake on Luzon Island. Viral Press/YouTube.

The geology of the Philippines is complex, with the majority of the islands located on the east of the Sunda Plate. To the east of this lies the Philippine Sea plate, which is being subducted beneath the Sunda Plate (a breakaway part of the Eurasian Plate); further east, in the Mariana Islands, the Pacific Plate is being subducted beneath the Philippine Sea Plate. This is not a smooth process, and the rocks of the tectonic plates frequently stick together before eventually being broken apart by the rising pressure, leading to Earthquakes in the process.
 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.
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Sunday, 21 April 2019

Asteroid 2019 GS19 passes the Earth.

Asteroid 2019 GS19 passed by the Earth at a distance of about 743 000 km (1.93 times the average distance between the Earth and the Moon, or 0.50% of the distance between the Earth and the Sun), slightly before 7.35 am GMT on Thursday 11 April 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 GT19 has an estimated equivalent diameter of 14-45 m (i.e. it is estimated that a spherical object with the same volume would be 14-45 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 10 km above the ground, with only fragmentary material reaching the Earth's surface.

The calculated orbit of 2019 GS19. Minor Planet Center.

2019 GS19 was discovered on 11 April 2019 (the day of its closest approach to the Earth) by the Palomar Transient Factory at Palomar ObservatoryThe designation 2019 GS19 implies that it was the 474th asteroid (asteroid S19 - 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 T19 = 18 + (24 X 19) = 474) discovered in the first half of April 2019 (period 2019 G).

2019 GS19 is calculated to have an 1015 day orbital period and an eccentric orbit tilted at an angle of 6.59° to the plane of the Solar System, which takes it from 0.82 AU from the Sun (i.e. 82% of the the average distance at which the Earth orbits the Sun) to 3.14 AU from the Sun (i.e. 314% of the average distance at which the Earth orbits the Sun, more than twice the distance at which the planet Mars orbits). 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 the Earth occur occasionally, with the last calculated to have happened in April 1924 and the next predicted for May 2196. The asteroid also has occasional encounters with the planet Mars, with the last thought to have occurred in September 2007.

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Avalanche on Des Poilus Glacier kills one in British Columbia.

A man has died following an avalanche on the Des Poilus Glacier in Yoho National Park, British Columbia, according to Parks Canada. The man was one of three people on the glacier when the avalanche hit at about 1.00 pm on Saturday 20 April 2019, and the only one injured in the incident. He was airlifted to the Foothills Medical Centre in Calgary, but later died of his injuries.

The approximate location of the 20 April 2019 Des Poilus Glacier avalanche. Google Maps.

Avalanches are caused by the mechanical failure of snowpacks; essentially when the weight of the snow above a certain point exceeds the carrying capacity of the snow at that point to support its weight. This can happen for two reasons, because more snow falls upslope, causing the weight to rise, or because snow begins to melt downslope, causing the carrying capacity to fall. Avalanches may also be triggered by other events, such as Earthquakes or rockfalls. Contrary to what is often seen in films and on television, avalanches are not usually triggered by loud noises. Because snow forms layers, with each layer typically occurring due to a different snowfall, and having different physical properties, multiple avalanches can occur at the same spot, with the failure of a weaker layer losing to the loss of the snow above it, but other layers below left in place - to potentially fail later.

 Diagrammatic representation of an avalanche, showing how layering of snow contributes to these events. Expedition Earth.

Des Poilus Glacier is located on Mount Des Poilus, which rises to 3166 m above sealevel, and 466 m above the surrounding plain, in the Waputik Mountains (a subrange of the Rockies). The mountain has a subarctic climate with temperatures reaching as low as -30°C in winter, when significant snow can accumulate, feeding the glacier, as well as the Yoho, Amiskwi, and Kicking Horse rivers. In spring the the area encounters warmer weather, leading to significant melting and frequent avalanches. 

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Landslide kills at least fourteen in Valle del Cauca, Colombia.

Fourteen people have now been confirmed dead and another five injured following a landslide in the municipality of Rosas in the Valle del Cauca Department of Colombia. The incident happened early in the morning of Sunday 21 April 2018, following several weeks of heavy rain in the area. 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. The landslide is reported to have buried eight houses and a portion of the Pan-American Highway under several tonnes of mud, and rescue workers are still searching for more people potentially buried under the debris.

Rescue workers at the scene of the 21 April 2019 Rosas landslide. Camilo Fajardo/AFP.

Valle del Cauca area has a wet tropical climate with a double monsoon, which peaks in April and October. Such a double Monsoon Season is common close to the equator, where the Sun is highest overhead around the equinoxes and lowest on the horizons around the solstices, making the solstices the coolest part of the year and the equinoxes the hottest.

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

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.

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