Saturday, 23 June 2018

Magnitude 5.1 Earthquake on the Paria Peninsula, Venezuela.

The United States Geological Survey recorded a Magnitude 5.1 Earthquake at a depth of 106 km roughly beneath the Paria Peninsula on the north coast of Venezuela, slightly before 9.55 pm local time on Friday 22 June 2018 (slightly before 1.55 am on Saturday 23 June 2018 GMT). This was a large quake, but at some depth as well as some way offshore, and there are no reports of any casualties or damage, though the quake was felt over a large area, with people reporting feeling it across much of northeast Venezuela, as well as in Trinidad and Tobago, and Grenada.
The approximate location of the 22 June 2018 Paria Peninsula Earthquake. USGS.
The Paria Peninsula forms part of the southern margin of the Caribbean Plate, which is moving eastward compared to the South American Plate, upon which the rest of Venezuela sits. This is not a smooth process, the two plates constantly stick together, then break apart as the pressure builds up, causing Earthquakes in the process. 
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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Thirteeen people killed in a series of landslides and flash floods in and around Hpakant, Myanmar.

At least thirteen people died in a series of landslides around the mining town of Hpakant in Kachin State, Myanmar, on Friday 22 June 2018. Four people are known to have died in a landslip on a spoil heap in the Sithu Mining Block, and it is feared that others may be unaccounted for in this incident (spoil-heap workers, known as Yay Ma Say, are often reluctant to discuss their activities with outsiders, even rescue workers, due to the legally dubious nature of the work), while seven are known to have died in a similar incident at Seikmu, while two women died in a flash flood the town of  Hpakant itself. 

 Houses undermined by a flash flood in Hpakant, Myanmar, on 23 June 2018. Myanmar International Television.

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.

The incidents occurred following several hours of rain in the area associated with the Southeast Asian Southwest Monsoon, which has also caused a series of landslips and flash floods 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. This year's monsoon has been particularly severe, with floods and landslips occurring across Myanmar.

The approximate location of the town of Hpakant. Google Maps.

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.

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

Much of Southeast Asia has two distinct Monsoon Seasons, with a Northeast Monsoon driven by winds from  the South China Sea that lasts from November to February and a Southwest Monsoon driven by winds from the southern Indian Ocean from March to 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. However Myanmar is largely protected from the Northeast Monsoon by the mountains separating the country from Yunnan Province in China.
 The winds that drive the Northeast and Southwest Monsoons in Southeast Asia. Mynewshub.
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Shinmoedake volcano eruption on Friday 22 June 2018.

Mount Shinmoedake, a 1421 m volcano that part of the Kirishima Volcanic Complex on southern Kyūshū Island, erupted again on the morning of Friday 22 June 2018, producing a column of ash that rose several kilometres above the summit of the volcano and and through fragments of rock over 1100 m from the caldera. This is the latest in a series of erutpions on the volcano, which began in October 2017, after a six year period of inactivity.

Ash column over Mount Shinmoedake, Japan, following an eruption on Friday 22 June 2018. Reuters.

Japan has a complex tectonic situation, with parts of the country on four different tectonic plates. Kyūshū Island lies at the northeast end of the Ryukyu Island Arc, which sits on top of the boundary between the Eurasian and Philippine Plates. The Philippine Plate is being subducted beneath the Eurasian Plate, in the Ryukyo Trench, to the Southeast of the Islands. As it is drawn into the interior of the Earth, the tectonic plate is partially melted by the heat of the Earth's interior, and liquid magma rises up through the overlying Eurasian Plate to form the volcanoes of the Ryukyu Islands and Kyūshū.

The movement of the Pacific and Philippine Plates beneath eastern Honshu. Laurent Jolivet/Institut des Sciences de la Terre d'Orléans/Sciences de la Terre et de l'Environnement.

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Friday, 22 June 2018

Seven dead in Mexico flooding.

Seven people have died in flooding in Mexico this week. On Friday 15 June 2018 a fourteen-year-old boy was swept into a storm drain in Mexico City and drowned, On Tuesday 19 June a woman and a teenage girl died of carbon monoxide poisoning while trapped in a car caught in floodwaters in Aguascalientes, while a landslide killed a man in Guanajuato. 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.On Wednesday 20 June a forty-year-old man drowned in Mexico City, and two people were electrocuted when they touched power cables after climbing onto buildings to escape floodwaters, one in Mexico City and another in the city of Matamoros in Tamaulipas State. Flooding has also been reported in Texas as far north as Houston.

Cars caught in floodwater in Aguascalientes on Tuesday 19 June 2018. Mexico Daily News.

Rainfall in eastern Mexico an southern Texas is driven principally by evaporation of water from the Caribbean, an area which has been suffering exceptionally high temperatures this year. However the flooding has also been linked to rapid urban expansion in many area, which has led to building on areas of historic wetlands, reducing the ability of the ground to absorb water and leading to surface flooding.

Flooding in Weslaco, Texas, on 20 June 2018. Joel Martinez/The Monitor/AP.

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