Sunday, 27 September 2015

Eclipse of the Supermoon.

A total Lunar Eclipse will occur on 28 September 2015, starting at about ten minutes past midnight GMT. It will be visible across much of Western Europe and West Africa, as well as Eastern North America, and all of South America and the islands of the Atlantic and Caribean. Part of the eclipse will be visible from remaining areas of North America, Africa and Europe as well as western Asia and many islands in the Pacific and Indian Oceans, although in these areas the Moon will either rise part way through the eclipse, or set before it is complete.

Areas from which the 28 September 2015 Lunar Eclipse will be visible. In the white area the full extent of the eclipse will be visible, in the shaded areas it will either begin before the Moon rises or end after the Moon has set, while in the darkest area it will not be visible at all. HM Nautical Almanac Office.

The Moon produces no light of its own, but 'shines' with reflected light from the Sun. Thus at Full Moon the Moon is on the opposite side of the Earth to the Sun, and its illuminated side is turned towards us, but at New Moon the Moon is between the Earth and the Sun, so that its illuminated side is turned away from us.

Lunar eclipses occur when the Moon passes through the Earth's shadow. This can only happen at Full Moon (unlike Solar Eclipses, which happen only when the Moon passes between the Earth and the Sum, and therefore only occur at New Moon), but does not happen every Lunar Month as the Sun, Moon and Earth are not in a perfect, unwavering line, but rather both the Earth and the Moon wobble slightly as they orbit their parent bodies, rising above and sinking bellow the plane of the ecliptic (the plane upon which they would all be in line every month).

Because the Moon is passing through a shadow, rather than being blocked from our view, it does not completely disappear during an eclipse like the Sun, but rather goes through two distinct phases of dimming, the Penumbra, when it is still partially illuminated by the Sun, and the Umbra, when the Earth completely blocks direct sunlight from the Moon. This does not result in complete darkness, as the Moon is still partially lit by reflected Earthlight, but it does turn a deep, dark red colour.

Phases of the Lunar Eclipse that will be seen on 28 September 2015. The times are given in GMT, to the nearest 10th of a minute, thus 03.23.5 represents 30 seconds after 3.23 am GMT. HM Nautical Almanac Office.

This lunar eclipse promises to be particularly spectacular, as it occurs on the night of the lunar perigee, i.e. the night when the Moon is closest to the Earth in this lunar month making it appear larger in the sky, with the center of the Moon only 358 876 km from the center of the Earth. The Moon completes one orbit about the Earth every 27.5 days, and like most orbiting bodies, its orbit is not completely circular, but slightly elliptical, so that the distance between the two bodies varies by about 3% over the course of a month. This elliptical orbit is also not completely regular, it periodically elongates then returns to normal, making some perigees closer than others. This September's perigee will be the closest of the year, and the closest since 8 September 2015, when the center of the Moon was only 358 387 km from the Center of the Earth.

Simplified diagram of the Moon's orbit. NASA.

See also...

A partial Solar Eclipse will occur on Sunday 13 September 2015, visible from all of Namibia, Botswana, South Africa, Lesotho, Swaziland, Zimbabwe and Reunion Island and parts of Angola, Zambia, Mozambique, Madagascar and Antarctica. The eclipse will occur between 4.41 am and 9.06 am GMT.

A total Lunar Eclipse will occur on a April 2015, starting at about 9.00 am GMT. It will be visible across much of the Pacific, as well as most of Alaska, the Russian...

A total eclipse of the Sun will be visible from the Faroe Islands and Svalbard on Friday 20 March 2015, with a partial eclipse visible from the rest of Europe, West Asia, northern Arabia, North and West Africa, Iceland, Greenland and (briefly) Nova Scotia, Newfoundland and Labrador and parts of eastern Quebec. 

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Saturday, 26 September 2015

Magnitude 2.8 Earthquake in Rutland, England.

The British Geological Survey recorded a Magnitude 2.8 Earthquake at a depth of 2 km about 2 km to the east of the village of Ashwell in Rutland, England, at about 10.40 pm British Summertime (about 9.40 pm GMT) on Tuesday 22 September 2015. There are no reports of any damage or injuries associated with this event, though it was exceptionally large for an English Earthquake, and people have reported feeling it from as far away as Burton-upon-Trent and Northampton.

The approximate location of the 22 September 2015 Rutland Earthquake and locations where people have reported feeling the event. British Geological Survey.

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 2.2 Earthquake at a depth of 8 km about 10 km to the south of...

The British Geological Survey recorded a Magnitude 1.4 Earthquake at a depth of 2 km about 10 km to the east of Loughborough in Leicestershire, England, slightly after 6.00 pm...

The British Geological Survey recorded a Magnitude 3.8 Earthquake at a depth of 8 km between the villages of Ashwell and Market Overton in Rutland, England, at about 10.25 pm GMT on Wednesday 28 January 2015. There are no reports of any damage or injuries associated with this event, though it was exceptionally large for an English Earthquake, and people have reported feeling it from as far away as Dudley in the West Midlands and...

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Heartland Virus found in wild Vertebrates in 13 US states.

The first known cases of Heartland Virus, a form of Phlebovirus in the Family Bunyaviridae, were reported in northwest Missouri in 2009, were two agricultural workers were struck down with an illness that causes fever, leukopenia (a decrease in the number of white blood cells in the blood) and thrombocytopenia (decrease in the number of platelets in the blood). The Virus which caused this disease was subsequently isolated from Lone Star Ticks, Amblyomma americanum, suggesting that this species acted as a vector for the disease, which presumably had a reservoir in some unknown wild (or possibly domestic) animal, however no such host species was located at the time. Further cases of the disease have subsequently been reported in Tennessee and Oklahoma, suggesting that the disease may present an emerging threat to Human health in parts of the US.

A Lone Star Ticks, Amblyomma americanum, the only known vector for the Heartland Virus. James Gathany/Centers for Disease Control/Wikimedia Commons.

In a paper published in the journal Emerging Infectious Diseases on 11 September 2015, Kasen  Riemersma of the Division of Vector-Borne Diseases at the Centers for Disease Control and Prevention in Fort Collins, Colorado and the University of California, Davis, and Nicholas Komar, also of the  Division of Vector-Borne Diseases at the Centers for Disease Control describe the results of a survey for antibodies to the Heartland Virus in wild animals from 19 US states (antibodies are produced by the body to help fight off diseases; an animal exposed to a disease retains the ability to produce antibodies against it for life).

Riemersma and Komar tested blood samples from White-tailed Deer, Odocoileus virginianus, and Racoons, Procyon lotor, two animals common in the area where Heartland Virus was first discovered and thought likely to be possible reservoirs for the Virus, as well as Moose, Alces alces and Coyote, Canis latrans, in Alabama, Florida, Georgia, Illinois, Indiana, Iowa, Kansas, Kentucky, Maine, Missouri, New Hampshire, North Carolina, Ohio, Pennsylvania, Tennessee, Texas, Vermont, Virginia and West Virginia.

State-level distribution of Heartland virus case reports in humans and seropositive wildlife, central and eastern United States, 2009–2014. Red indicates states with seropositive animals; gray indicates states with no seropositive animals. Year labels indicate the earliest year of detected HRTV activity. Earliest detection was determined by human case reports in Missouri (1 case) and Oklahoma (3 cases) and wildlife serologic data in all other states. Riemersma & Komar (2015).

The Virus was found in all four species of animals, and was detected in Florida, Georgia, Illinois, Indiana, Kansas, Kentucky, Maine, Missouri, New Hampshire, North Carolina, Tennessee, Texas, and Vermont. This includes Deer in several states in New England, an area where Lone Star Ticks are not found, and while Deer are capable of migrating long distances across state boundaries, these states were not contiguous with other states where Heartland Virus has been found.

However, at least one other member of the genus  Phlebovirus, Thrombocytopenia Syndrome Virus, which is found in eastern Asia, is known to be spread by several different species of Ticks, suggesting that this might also be the case for Heartland Virus.

See also...

Thrips (the word is both singular and plural),Thripidae, are very small Insects with wings reduced to feathery growths (though this is sufficient to support them in flying due to their small size). They feed by sucking fluids from plants, and as such are important agricultural pests, both for their ability to damage plants...

In late spring 2014 a previously healthy man in his 50s was admitted to a hospital in Bourbon County, Kansas, suffering from Tick bites and a fever. Despite intensive care and treatment with broad-spectrum anti-microbial drugs he died of cardiopulmonary arrest brought on by multiple organ failure eleven days after the onset of the illness. Tests for a wide variety...

In December 2013 cases of the haemorrhagic Virus Ebola began to be reported from the village of...

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Thursday, 24 September 2015

Stick Insects of the Mascarene Islands.

The Mascarene Islands, Mauritius, Réunion and Rodrigues, lie in the western Indian Ocean, to the east of Madagascar and to the south of the Seychelles. They form part of a chain of biodiversity hotspots across the eastern Indian Ocean, where many islands and island groups have developed unique faunas and floras seen nowhere else. However, while Madagascar and the Seychelles are continental fragments left over from the breakup of Gondwana and started as islands with some unique fauna, the Mascarene Islands are of volcanic origin, formed by hotspot volcanism in a similar way to Hawaii or the Canary Islands, and all of the flora and fauna there must have reached the islands since they first rose above the waves, about 8-10 million years ago in the case of Mauritius, the oldest and largest of the islands.

Much of the fauna of the Mascarenes, shows a close affinity with that of Madagascar, the largest landmass in the southeast Indian Ocean and only 700 km from Mauritius. Mascarene Groups such as Day Geckos, Slit Eared Skinks, Giant Tortoises, Land Snails and Orb Spiders have all been shown to have originated from Madagascar. Other animals have been shown to be of Indo-Pacific origin, having apparently descended from animals that crossed the 5600 km of open-ocean from Australia or 7000 km from New Guinea. This group includes the famous but extinct Dodos and Solitaires, Skinks of the genus Leilopisma and Geckos of the genus Nactus.

The Stick Insects, Phasmatodea, of the Mascarenes present a unique problem to biogeographers, as they include members of four different subfamilies and one species of uncertain origin, apparently implying repeated colonization of the islands by members of different Stick Insects from different areas. Given the remoteness of the Mascarene Islands, this would be implausible for a group of flying, wide-ranging Insects, and is highly unlikely for Stick Insects, which have only very weak flying abilities, being able to slow their descent when falling from a tree, but not to make long, trans-oceanic migrations.

In a paper published in the journal BMC Evolutionary Biology on 16 September 2015, Sven Bradler of the Johann-Friedrich-Blumenbach-Institute of Zoology andAnthropology at the Georg-August-University Göttingen, Nicolas Cliquennois of the Collège français in Antsirabe, Madagascar and Thomas Buckley of Landcare Research, the School of BiologicalSciences at The University of Auckland and the Allan Wilson Centre, describe the results of a genetic study of the origin of Mascarene Stick Insects, which included data from 120 species of Stick Insects from around the globe, including seven species from Mauritius and three from Réunion (the single described Stick Insect species from Rodrigues, Xenomaches incommodus, is thought to be extinct, and no material was available for inclusion in the study).

Mascarene stick insects. (a) Couple of Apterograeffea reunionensis (Platycraninae) from Réunion. (b) Male of Epicharmus marchali (Xeroderinae) from Mauritius. (c) Female of Rhaphiderus spiniger (Tropidoderinae) from Réunion. Bradler et al. (2015).

Bradler et al. found that, contrary to expectations, all of the Mascarene Stick Insects belonged to a single lineage within the Lanceocercata, an Australasian group, having split from their closest Australian relatives about 27.15 million years ago, and with all the Mascarene Island Stick Insects having shared a last common ancestor that lived about 22.03 million years ago. The group has subsequently diversified into a number of forms that closely resemble members of other groups through convergent evolution, i.e. evolving the same traits to deal with similar ecological problems. For example, the Mascarene genus Apterograeffea has been considered to be a member of the Platycraninae (Coconut Stick Insects), closely resembling members of this group due to also having greatly enlarged cheeks, which support extra muscles which support the mandibles when chewing on tough foliage, while the Mauritian Epicharmus has been assigned to the Xeroderinae, resembling several members of this group with which it shares the habit of living on tree bark.

Chronogram of the sampled stick insect specimens with taxa distributed across the Indian Ocean highlighted in tones of red. Numbers at nodes indicate bootstrap values (left) and clade posterior probabilities (right); grey bars show 95 % highest probability density. Circled numbers refer to fossil calibration points: (1) Renphasma, (2) Eophasma, (3) fossil Malacomorpha, (4) fossil Clonistria. Abbreviations: Pl, Pliocene; Qu, Quaternary. Bradler et al. (2015).

This timescale is slightly problematic for the colonisation of the Mascarene Islands, as it requires the Stick Insects to have separated from their Australian relatives and begun diversifying into newly available niches considerably before the origin of the islands.

However, the Mascarene islands are of volcanic origin, the latest in a chain of islands formed by the movement of a volcanic hotspot, the Réunion Hot Spot, moving southwards across the Indian Ocean. Volcanic hot spots are formed where deep plumes of hot magma rising up from the Earth's interior intersect with the tectonic plates on the surface of the planet. Since these plumes originate deep within the mantle, their movement at the surface is independent of the movement of the tectonic plates. This means that while the currant Mascarene Islands, Mauritius, Réunion and Rodrigues, are quite young, a chain of previous islands, now sunken beneath the seas, extends northwards from them along the line of the volcanic hotspot.

Bradler et al. reason that the Mascarene Island Stick Insects could have originally colonised one of these sunken islands, most probably Siant Brandon, which lies 385 km to the northeast of Mauritius and which first emerged from the sea about 31 million years ago, or Nazareth Bank, slightly to the north of Saint Brandon, which first emerged about 35 million years ago, and subsequently colonised the current Mascarene Islands from these now sunken 'stepping stones', possibly via the smaller uprisings of Baissac Bank and Soudan Bank.

Dispersal scenario of Mascarene stick insects superimposed on a map of the Indian Ocean. (a) Current map of the Indian Ocean. (b) Enlarged view of Mascarene plateau. Red arrows indicate postulated colonisation events: The ancestral Mascarene stick insect arrived on currently submerged islands located to the North of Mauritius followed by a radiation and at least three (maximal six) independent dispersals to Mauritius and another three dispersals to Réunion, most likely facilitated by ocean currents. Bradler et al. (2015).

See also... 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...

Syzygium pyneei: A new species of Myrtle from Mauritius. 
The genus Syzygium is the largest within the Myrtle family, Myrtaceae, with over 1200 described species from across the tropical and subtropical regions of the Old World, including fifteen previously described species from Mauritius. on Piton de la Fournaise, Réunion Island.                                          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...
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Monday, 21 September 2015

September Equinox 2015.

The September Equinox will fall on Friday 23 September 2015, when the day and night will be of equal length in both of the Earth's hemispheres. The Earth's seasons are driven by the tilt of the planet, but the planet does not, as is generally assumed, tilt back and forth over the course of a year. Rather it remains at a constant angle of 23½° to the plane of its orbit throughout the year (this does alter on a longer cycle, but not one that matters on human timescales), but this tilt is disconnected from its orbit about the Sun, with the effect that the Northern Hemisphere is presented towards the Sun from one side of the orbit (creating the northern summer and the southern winter), and the southern hemisphere from the other (creating the southern summer and the northern winter).

Simplified diagram showing the tilt of the Earth throughout the year. Not to scale. NASA.

At two points in the year the Earth presents the two hemispheres equally to the Sun (though it is still tilted at 23½° to the plane of its orbit), creating the equinoxes, which fall in March and September each year. The September Equinox, marks the end of summer in the northern hemisphere (where it is the Autumn or Fall Equinox) and the beginning of summer in the southern hemisphere (where it is the Spring Equinox).

See also...

A partial Solar Eclipse will occur on Sunday 13 September 2015, visible from all of Namibia, Botswana, South Africa, Lesotho, Swaziland, Zimbabwe and Reunion Island and parts of Angola, Zambia, Mozambique, Madagascar and Antarctica. The eclipse will occur between 4.41 am and 9.06 am GMT.

The Earth will reach its aphelion, the furthest point in its orbit from the Sun, a distance of 152 093 481 km, at 7.41 pm GMT on Monday 6 July 2015. The Earth's orbit is slightly eccentric and slightly variable, leading to the distance between the Earth and the Sun varying...

The June (or Northern) Solstice falls on Sunday 21 June in 2015, the day on which the Sun rises highest in the sky and the longest day of the year in the Northern Hemisphere (where it is the Summer Solstice) and...

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Sunday, 20 September 2015

Evidence for feeding on schooling shallow-water Fish by a Miocene Beaked Whale.

Beaked Whales, Ziphiidae, are small-to-medium sized Toothed Whales, Odontoceti, which hunt Fish, Cephalopod Molluscs and Crustaceans using echo-location in a similar way to Dolphins. However unlike Dolphins they are specialized for deep-diving, generally feeding at depths ranging from a few hundred to a few thousand meters. This is apparently a very successful strategy, as the group comprise about 25% of all living Whale species. However while all crown group Beaked Whales (the crown group comprises all living members of a group, their last common ancestor, and everything descended from it) are either living species known to practice deep-water diving or show adaptations to deep-water diving, such as fused vertebrae, reduced flipper sizes, enlarged sinuses and reduced dentition, the feeding habits of stem-group Beaked Whales (the stem group comprises members of a group descended from the last ancestral species not thought to have given rise to any living species outside the crown group, i.e. species more closely related to the crown group than to any other group, but still outside the crown group) is less clear, with the transition between shallow-water feeding and deep-diving thought to have occurred somewhere in this group.

In a paper published in the Proceedings of the Royal Society Series B: Biological Sciences on 9 September 2015, a team of scientists led by Olivier Lambert of Terre et Histoire de la Vie at the Institut royal des Sciences naturelles de Belgique, describe the discovery of a remarkable death-assemblage in the Late Miocene Pisco Formation at Cerro Colorado in southern Peru, comprising a stem-group Beaked Whale and a large number of Clupeiform Fish (Herring), thought to be closely related to the modern Pacific Sardine, Sardinops sagax.

The Pisco Formation comprises two fining-uppward sequences (sequences in which the particle sizes grow smaller upwards) ranging from course conglomerates (sediments containing mixed pebble-sized rocks with an infilling of sand or finer particles, typically associated with beaches, river beds or similar environments) to diatomaceous mudstones (sediments comprising fine clay particles and the shells of planktonic Diatoms, typically formed far from shore in the sea or a wide lake), and separated by an unconformity (missing section in a stratigraphic sequence, typically caused by exposure of the rocks and erosion associated with a drop in sealevel), dated to between 9.9 and 8.9 million years old by the presence of the Late Miocene marine Diatom Lithodesmium reynoldsii. This formation has produced a rich assemblage of vertebrate fossils, including Sperm Whales, Beaked Whales, Dolphins, Baleen Whales, Turtles, Crocodiles, Seabirds, Sharks and Bony Fish.

The specimen described by Lambert et al. comprises a Beaked Whale assigned to the species Messapicetus gregarius, which is well documented from the Pisco Formation with at least ten known specimens, thought likely to have been female and estimated to have been between 4.1 and 4.5 m in length. This specimen was buried in an inverted position (upside down) with between 40 and 60 well-articulated Bony Fish skeletons surrounding the head and apparently within the chest cavity. These Fish average 38.8 cm in length, with very little variation, and are placed within the Pacific Sardine genus, Sardinops, and are thought to have been very similar to the modern Pacific Sardine, Sardinops sagax.

Lambert et al. believe that these fish represent the last meal of the Whale, which has been partially regurgitated following the Whale’s death. They cite a number of lines of evidence to support this theory. Firstly the Whale and Fish skeletons are located within exactly the same stratigraphic layer, and are all well-articulated, suggesting they died within a short time-span of one-another. Secondly the Fish are found only around the head and body cavity of the Whale, positions consistent with a regurgitated meal. Thirdly, despite the rich fossil fauna of the formation, this is the only locality where these Sardines are found, other than a few isolated scales and bones, and the only Bony Fish death assemblage, suggesting that the locality does represent a unique localized event, rather than the fortuitous deposition of a Whale skeleton within a wider Fish bone-bed layer. Fourthly modern Pacific Sardines consume only planktonic Crustaceans, not large vertebrate carrion, making it unlikely that these very similar Miocene Fish were feeding on a dead Whale when they died. Fifthly the size of the Fish closely matches the size of Fish targeted by living toothed Whales of a similar size to the Pisco Formation specimen. Finally the size and number of Fish suggests a total mass of about 25 kg, roughly the same as the masses of Fish produced by stomach content analysis of extant Toothed Whales of similar size.

Fossil remains of the extinct beaked whale Messapicetus gregarious and associated Clupeid Fish Sardinops sp. cf. S. sagax found in Cerro Colorado. (a) Photograph and line drawing of the articulated caudal portion of a skeleton of Sardinops sp. in left lateral view (note the typically Clupeid urostyle supporting the caudal fin complex), with a complete skeleton of the modern sardine S. sagax for comparison. (b) Imbricated large cycloid scales of Sardinops sp. in right lateral view showing tubercular protuberances in their central region and curved radii-like lines in their lateral fields, with a body of S. sagax for comparison reporting the putative collocation of the scale set. (c) Dolomite concretion with the skull and mandibles of M. gregarious in ventral view; occipital region, hamular processes of the pterygoids, posteroventral and apical regions of the mandibles emerge from the concretion. Abbreviations: bv, articulated bivalve shells; mda, apex of mandibles; mdp, posteroventral part of mandibles; ph, hamular processes; wd, fragment of fossilized wood. (d) Line drawing of the skull of M. gregarious inside the concretion with a reconstructed outline of its body. Multiple individuals of Sardinops sp. found around the head and in the chest region are schematically represented. Stippled line marks the outline of the concretion. Lambert et al. (2015).

The cause of death of the Whale is not immediately obvious. The specimen appears to have been relatively healthy at the time of death, not showing any signs of illness or malnutrition, and apparently feeding normally (typically sick Whales have difficulty feeding). It shows no sign of physical injury, which would be expected if it had been the subject of an attack by a predator such as a large Shark or Sperm Whale. Lambert et al. suggest that it may have died as a result of poisoning, due to toxins produced by a bloom of single-celled algae. Such blooms are a known cause of death in modern Whales, who can either consume the toxic algae along with desired prey, or be poisoned by consuming prey that had itself ingested the harmful algae. The Pisco Formation is known to show evidence by testate (shelled) single-celled algae, and while there is no evidence of such a bloom around the Whale find, lethal toxins are more usually associated with algae that lack shells. Such algal blooms do not (and cannot) occur in deep water, as the algae that produce them are reliant on sunlight to grow.

Modern Pacific Sardines form shoals of the same age, and therefore size, remaining with these individuals throughout their lives. All of the Sardines found at the Pisco Formation Whale death site are of approximately the same size, suggesting that these Fish exhibited similar behaviour.

Life reconstruction of three individuals of the extinct Beaked Whale Messapicetus gregarious preying upon a school of aged Sardines Sardinops sp. (average body length 38.8 cm) in the upper part of the water column along the coast of present-day Peru. The front individual is an adult male, whereas the last in the background is a female. Alberto Gennari in Lambert et al. 2015).

Modern crown group Beaked Whales are all deep-water feeders, but the ancient stem group Beaked Whales from which they descend lack the specialist adaptations that enable their descendants to do this, suggesting that they were shallow-water feeders. This theory is supported by the discovery of a Whale from the Miocene of Peru which apparently died shortly after feeding in a shallow-water environment. The last of these stem-group Beaked Whales appear to have lived around the end of the Miocene, after which they disappeared, leaving only the crown group Beaked Whales, which appeared in the Middle Miocene and which feed in deeper waters. This disappearance of the shallow-water Beaked Whales coincides with the appearance of modern Dolphins towards the end of the Miocene, a group which radiated rapidly and spread quickly around the globe. Lambert et al. suggest that these early Dolphins may have competitively excluded Beaked Whales from shallow water environments, leading to the demise of the stem group Beaked Whales.

Phylogenetic tree illustrating the relationships between extant and part of the extinct Ziphiids. The outgroup is the Eurhinodelphinid Xiphiacetus. Red lines indicate stratigraphic ranges. Dotted lines indicate uncertainty for the age of some members of a genus. Separation between epipelagic and deep-diving taxa is based on morphology, platform versus deep-sea deposits for fossil taxa, stomach content analysis for Messapicetus, and optimization of the deep-diving ecology of most extant genera on the phylogenetic tree. Lambert et al. 2015).

See also…

There are four species of River Dolphins known today; Inia geoffrensis and Pontoporia blainvillei from South America, Platanista gangetica from South Asia and the probably extinct Lipotes vexillifer from China (Lipotes vexillifer, the Yangtze River Dolphin, is considered Critically Endangered under the terms of...

Whales are highly specialized carnivorous Marine Mammals, with morphologies highly adapted to an aquatic lifestyle. Their closest relatives, the Artiodactyls, are terrestrial herbivores (and occasionally omnivores), with a very different lifestyle and hence anatomy. This means that almost every aspect of the Whales’...

Porpoises, Phocoenidae, are small Dolphins, Delphinida, found today across most of the world’s oceans, but with a fossil record restricted almost entirely to the North Pacific. Only a single fossil species from outside the Pacific Basin has been described, Septemtriocetus bosselaersi from Pliocene sediments at Verrebroek Dock in Antwerp Harbour, Belgium, with...

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Fourteen confirmed deaths after Magnitude 8.3 Earthquake off the coast of Chile.

Fourteen people have now been confirmed dead following an Earthquake off the west coast of Chile on Wednesday 16 September 2015. The event happened slightly before 6.55 pm local time (slightly before 10.55 GMT) and was recorded by the United States Geological Survey as being a Magnitude 8.3 event at a depth of 25 km. The Earthquake itself caused relatively little damage, but triggered a tsunami that was felt around the Pacific basin and was almost 5 m high when it struck parts of the coast of Chile. It is thought that the number of casualties will still rise further, though a much higher number of deaths was avoided by prompt evacuations of low lying areas.

Tsunami damage in the city of Coquimbo on Thursday 17 September 2015. AP.

In addition to the thirteen confirmed fatalities in Chile one person is reported to have died in Argentina (an elderly man who fell down a flight of stairs in Buenos Aries during an evacuation). A further eleven people are known to have sustained serious injuries, and 262 homes are known to have collapsed in Chile and a further four in Argentina, while 420 homes were rendered uninhabitable due to damage in Chile and 82 in Argentina. Chile has also received significant damage to infrastructure, with over 14 000 people left without power and over 9000 without water in Chile, and damage to a number of civic buildings recorded in Argentina.

The approximate location of the 16 September 2015 Chilean offshore Earthquake. Google Maps.

Chile is located on the west coast of South America, which is also the convergent margin between the Nazca and South American Plates. The Nazca Plate is being subducted beneath the South American Plate and is sinking beneath the South American Plate. This is not a smooth process, the rocks of the two plates continuously stick together then, as the pressure builds up, break apart again, causing Earthquakes. As the Nazca Plate sinks deeper it is partially melted by the heat of the Earth's interior. Some of the melted material then rises up through the overlying South American Plate as magma, fueling the volcanoes of the Chilean Andes.

The subduction of the Nazca Plate beneath the South American Plate, and how it causes Earthquakes and volcanoes. Pacific Earthquake Engineering Research Center.

Earthquakes along subductive margins are particularly prone to causing tsunamis, since these often occur when the overlying plate has stuck to the underlying plate, being pulled out of shape by its movement.. Eventually the pressure builds up tp far and the overlying plate snaps back, causing an Earthquake and a tsunami. 

Simplified graphic showing tsunami generation along a convergent margin.NASA/JPL/CalTech.

Witness accounts of Earthquakes can help geologists to understand these events, and the structures that cause them. The international non-profit organization 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 times at which the tsunami caused by the 16 September 2015 earthquake reached different parts of the Pacific Basin. National Tsunami Warning Center.

See also...

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