Between a Rock and a Hard Place

Science Snap (#19): Angkor Wat, Cambodia

Charly Stamper February 13, 2014

Sorcha McMahon is a third year PhD student in the School of Earth Sciences at the University of Bristol. Sorcha is investigating how strange igneous rocks called carbonatites may have formed, using both natural samples and high-pressure experiments.

The word Angkor is derived from the Sanskrit term Nagara meaning “Holy City”, and was the capital city of the Khmer. It consists of successive city foundations and temples constructed by the kings of three dynasties over a period of about 600 years. The site is most famous for Angkor Wat, the largest religious monument in the world, which has been a part of the Cambodian national flag since the first version was introduced circa 1863.

View of Angkor Wat, Cambodia. The temple is part of the Angkor World Heritage Site, established in 1992. Photo credit: Sorcha McMahon

Angkor Wat was constructed under the rule of King Suryavarman II (reigned AD 1113 – 1150), and built in the form of Mount Meru, home of the Hindu gods. The main temple incorporates 5 towers, representing the peaks of Mt Meru, and is surrounded by ~1×1 km walls (‘mountain ranges’) and a moat (‘ocean’). The temple was built as a place to worship ancestors and as a mausoleum to receive the cremated remains of individual kings.

The temple beautifully displays the classical style of Khmer architecture. Over 5 million tons of sandstone was used in the temple’s construction. Rocks were transported by raft along the Siem Reap river from Mount Kulen, ~ 40 km to the north east. Laterite, a clay formed by weathering of rocks in the tropics, was also used for internal structure. Large blocks were laid without mortar, and it’s likely that elephants, ropes, pulleys and bamboo scaffolding were all employed in the construction. Today, holes in the blocks can be seen (~2.5 cm diameter and 3 cm deep), probably used to aid lifting the blocks into place using metal rods. Angkor Wat was completed in around 40 years (the duration of the king’s reign), although a modern engineer estimated that it would take 300 years to complete Angkor Wat today!

Much of Angkor Wat’s sandstone surface was apparently once covered in gold, and other temples in the area were originally red (painted using tree resin). Bas-relief friezes (low relief images typical of Hindu-Buddhist arts in India and SE Asia) dominate the decoration. Imagery includes the king, his court, and iconographic scenes drawn from the Hindu religion. Apsaras (female spirits of the clouds and waters in Hindu and Buddhist mythology) and devatas, from the Hindu term for ‘Deva’ meaning deity, are abundant; there are more than 1796 depictions of devata in the present research inventory.

Intricate bas-relief on the ceiling and walls inside Angkor Wat. Remnants of the original red colour has been partially preserved.

Intricate bas-relief on the ceiling and walls inside Angkor Wat. The original red colour has been partially preserved. Photo credit: Sorcha McMahon

Sandstone carving of devata at Angkor Wat. Credit: Sorcha McMahon

Sandstone carving of devata at Angkor Wat. Photo credit: Sorcha McMahon

Science Snap (#18): Tragic Sinabung Eruption

Charly Stamper February 6, 2014

James Hickey is a PhD student in the School of Earth Sciences at the University of Bristol. A geophysicist and volcanologist by trade, his PhD project is focussed on attempting to place constraints on volcanic unrest using integrated geodetic modelling.

Last Saturday (1st February 2014) an eruption at Sinabung volcano in Indonesia claimed the lives of 14 people. That death toll has since risen to 16, and could rise further as people battle in hospital with severe burns and other wounds.

A local villager runs from the eruption of Sinabung volcano in Indonesia. Image credit: BBC News.

The volcano has been erupting since September 2013 and over 30,000 people have been evacuated from their homes. The Friday before the latest eruption, anxious citizens were allowed back to check on their homes. Many had been sneaking back into the exclusion zone anyway. And herein lies the danger. Despite the obvious inconvenience of being away from home for such a period of time, exclusion zones and evacuations are there for protection and safety. This tragic event is the result of people becoming too complacent around a volcano with a prolonged eruption, and locals not fully understanding the risks associated with such situations.

Hopefully this will serve as a timely reminder, to both locals and scientists. The perennial need for better communication between scientists, locals and civil protection authorities isn’t going away.

Science Snap (#17): Ailsa Craig

Charly Stamper January 30, 2014

Ailsa Craig is an uninhabited island off the west coast of Scotland. Formed from the plug of a Paleogene volcano, the landmass reaches over 330 m height and ~ 3 km length, and can easily be seen from the Scottish mainland. The island comprises three types of granite: Ailsa Craig Common Green, Ailsa Craig Red Hone and Ailsa Craig Blue Hone (pictured below). The distinctive colouration of the latter type results from the presence of riebekite and arfvedsonite, two amphiboles rich in sodium and iron.

The island of Ailsa Craig is most famous for being the source of material used to make most of the world’s curling stones. These unusual igneous rocks are particularly prized for their low thermal conductivity, impermeable fabric and relative elasticity, lending the stones unrivaled impact resistance. Watch out for these remarkable granites in Sochi; the stones for this year’s Winter Olympics have already been manufactured in Ayrshire and were shipped to Russia last year.

Left: South end of Ailsa Craig, South Ayrshire, Scotland, as viewed from the air. Right: Ailsa Craig Blue Hone (riebekite microgranite). Both images from the British Geological Survey National Archive of Geological Photographs (P000709 and P521397).

If you’ve ever wondered how curling stones are made (and I’m sure you have), then this video should sate your curiousity.

Science Snap (#16): Primary colours at Kawah Ijen

Charly Stamper January 23, 2014

Mel Auker is an Earth Sciences PhD student in the School of Earth Sciences at the University of Bristol. A mathematician by trade, Mel’s PhD uses numerical approaches to better understand past, present, and future global volcanic hazard and risk.

Kawah Ijen volcano forms part of the Ijen volcano complex situated at the eastern end of Java, Indonesia. Kawah Ijen is topped by a 1 kilometre-wide, 200 metre-deep, crater lake. The lake is bright turquoise in colour, and as well as being incredibly photogenic, is one of the most highly acidic lakes in the world and the site of a huge sulphur mining operation.

The summit of Kawah Ijen complete with acidic crater lake and sulphurous fumeroles. Photo credit: Richard Arculus

The Boston Globe has featured Kawah Ijen and its sulphur mine in two of its “The Big Picture: News stories in photographs” in recent years. The articles and accompanying stunning photographs can be found here and here.

The images depict the sulphur in its various, colourful states. Firstly, red, liquid sulphur condenses in stone or ceramic pipes that have been constructed to cap the volcano’s gas-emitting fumaroles. As this sulphur cools, it moves down the pipes and condenses to form yellow deposits. It is these solid deposits that the miners extract and carry in loads of up to 70kg to the weighing station, dubbed “Camp Sulfutara”. To enable them to earn more money, many miners work at night, illuminating the volcano by torch light. As the torches drip, they ignite the sulphur and it burns bright blue – the last of the primary colour trio.