Earthquakes and architecture – ancient and modern in Peru

By Lindsey Atkinson

Peru lies on the western side of South America: approximately 100 miles off the coast in the Pacific Ocean the Nazca plate is subducted under the South American plate forming the Peru-Chile (Atacama) Trench.  As a result Peru is subject to frequent earthquakes* and sometimes even tsunamis (e.g. 1996 and 2001). 

Adobe house

 Approximately two-thirds of Peru’s rural population live in adobe dwellings which are particularly vulnerable to collapse during an earthquake.  Adobes are made out of sun-baked clay bricks and it is only possible to build up to two floors.  Professor Marcial Blondet and his team at the Catholic University of Peru in Lima have been working to make adobe buildings safer (http://news.bbc.co.uk/1/hi/world/americas/8202498.stm) using a polymer mesh for reinforcement.  They recommend keeping buildings to one storey and keeping the size of openings to a minimum for greater strength. Today although people in rural areas still build their own adobe houses, in many towns most buildings are now constructed with steel reinforced concrete which allows for much taller structures.

Huaca Pucllana

How did ancient Peruvians cope with earthquakes without the benefits of modern technology?  The temple of Huaca Pucllana in Lima (http://huacapucllanamiraflores.pe/) was built by the Lima culture between 200 and 500 AD and is an adobe ‘pyramid’.   This mud structure, now partially reconstructed, has survived so long, partly due to the extremely low rainfall in the region, but also because of its construction with bricks placed vertically and spaced to allow for movement during earthquakes.

The Incas (1200-1542 AD) built with stone.  For example the temple of Qorikancha in Cusco (https://www.cuscoperu.com/en/travel/cusco/archaeological-centers/qorikancha) demonstrates fine masonry with large, well–fitting, rectangular blocks of stone.  No mortar was used, but a fine layer of sand between blocks allows for some movement during an earthquake.  The structure has inward sloping walls which provide stability and it is said that the trapezoid niches and doorways help dissipate the energy of seismic tremors.  Sites such as Sacsayhuaman near Cusco have well-fitting, but this time, irregular shaped blocks.  This degree of craftsmanship seems to have been reserved for religious sites and for the nobility: other sites have rougher stonework with mud mortar and square niches.  

Sacsayhuaman

Qorikancha

Lima Cathedral

The Spanish colonial builders were not so successful: many of their buildings collapsed during earthquakes, while Inca structures remained. For example, the convent of Santo Domingo in Cusco was built on top of Qorikancha, using the temple as its foundations but while the convent had to be rebuilt following the 1950 earthquake the Inca walls stood undamaged.  The cathedral in Lima dates from 1535 but has suffered damage following many earthquakes and in 1746 it was completely flattened.  The current building has wooden, rather than stone, columns and a wooden ceiling plus a policy of strictly no candles!  However, the catacombs beneath the nearby Monastery of Saint Francis, built of bricks and mortar, do seem to have survived quite well.  These crypts also include well-shaped structures which again are said to dissipate the lateral energy of a tremor.

Probably the most famous site in Peru is the citadel of Machu Picchu, abandoned shortly after the Spanish Conquest in the mid-1500s: one theory is that this was to prevent it from being found by the Spanish.  It remained hidden to all but local farmers until 1911 when it was rediscovered by the American explorer, Hiram Bingham.  The ability of these structures to withstand earthquakes is largely anecdotal and have not been proven, although modern techniques allow for better assessment of their earthquake protection properties (see Cuadra et al. 2008). So far Machu Picchu has proved to be remarkably earthquake resistant.

Machu Picchu

*Most recently on 15.08.16 (http://www.bbc.co.uk/news/world-latin-america-37084723)

Bibliography
Bankoff G. 2015. Seismic architecture and cultural adaptation to earthquakes. In: Krüger F, Bankoff G, Cannon T, Orlowski B, and Schipper L, eds. Cultures and disasters: Understanding cultural framings in disaster risk reduction. New York and London: Routledge.
Blondet M, Villa Garcia GM and Brzev S.  2003. Earthquake-Resistant Construction of Adobe Buildings: A Tutorial. Published as a contribution to the EERI/IAEE World Housing Encyclopedia, http://www.world-housing.net/wp-content/uploads/2011/06/Adobe_Tutorial_English_Blondet.pdf
Cuadra C, Karkee MB and Tokeshi K. 2008. Earthquake risk to Inca’s historical constructions in Machupicchu. Adv. Eng. Software 39: 336-345. http://dx.doi.org/10.1016/j.advengsoft.2007.01.002.
Smith J and Petley DN. 2007. Environmental hazards: assessing risk and reducing disaster. 5^th edn.  New York: Routledge.
Stewart A. 2013. The Inca Trail, Cusco and Machu Picchu. 5^th edn. Trailblazer Publications. Surrey, UK

Vanadium: the 'beautiful metal' that stores energy

Helena I. Gomes,  and Helen Abigail Baxter.
 
An unheralded metal could become a crucial part of the renewables revolution. Vanadium is used in new batteries which can store large amounts of energy almost indefinitely, perfect for remote wind or solar farms. And what’s more there is loads of the stuff simply lying around in industrial dumps.

Don’t let the dumpster diving put you off – never mind gold or silver, vanadium may just be the most beautiful metal of all. It’s the 22nd most abundant element in the Earth’s crust, though it’s rarely found naturally in its metallic form. Instead, vanadium can be found in more than 100 different minerals.

Colours of vanadium. Steffen Kristensen

Once extracted and dissolved in water, various forms of vanadium turn into bright, bold colours. It’s even named after “Vanadis”, the old Norse name for the Scandinavian goddess of beauty, Freyja.
Vanadium is not only beautiful, but also strong. Adding small percentages of it creates exceptionally light, tough and more resilient steel alloys. Henry Ford was the first to use it on an industrial scale, in the 1908 Model T car chassis, and today the vast majority of vanadium is used in structural steel, mainly to build bridges and buildings.

Vanadium flow batteries

The unique properties of vanadium make it ideal for a new type of batteries that may revolutionise energy systems in the near future – redox flow batteries.

Batteries store energy and generate electricity by a reaction between two different materials – typically solid zinc and manganese. In flow batteries, these materials are liquid and have different electric charges. Both are pumped into a “cell” where the electric current is generated. A tiny membrane separates the two liquids, so they are able to react but don’t come into direct contact.
Vanadium is used in these batteries as it can convert back and forth from its various different states, which can carry different positive charges. As only one material is used, the risk of cross contamination is eliminated. The liquids have an indefinite life, so the replacement costs are low and there are no waste disposal problems. Also, the battery is extended to a potentially infinite lifetime.

Vanadium flow batteries.

In flow batteries, the energy production and capacity are independent. Energy is stored in tanks, whereas the capacity depends only on the amount of liquid stored. This provides a great design flexibility that other batteries do not allow. They are also safer, as the two liquids don’t mix causing a sudden release of energy. Even President Obama is impressed.

The new energy reservoir

Vanadium flow batteries are too big and heavy to replace the lithium batteries found in your phone, however. These batteries are instead used for large stationary long-term energy storage, or to supply remote areas, or provide backup power. They’re the basis for a more efficient, reliable, and cleaner electrical energy market.

Energy storage is one of the main factors limiting the spread of renewables. When solar and wind power is produced at the wrong time of day we need to store it to use it during the evening demand peaks. Studies have shown that vanadium batteries can be a sustainable solution.

When we can create huge stores of energy to access as required, we will be liberated from the need to maintain rapidly-accessible energy generation such as coal or gas. Vanadium batteries can be a reservoir of energy much in the same way as we use actual reservoirs to store rainwater for later use.

Strengthened with vanadium. The Henry Ford / Life magazine

The ability to store electricity would reduce reliance on gas and coal. In turn this would increase fuel security and cut CO₂ emissions, helping to meet agreed emissions targets. No wonder then that the EU considers vanadium a critical metal for strategic energy technologies.

The hunt for vanadium

The metal is mined, and supplies are currently dominated by China, South Africa, Russia and the US. Vanadium has a medium risk of supply shortage and a high political risk.

However, as vanadium can be a byproduct of other sorts of mining, about 70% of the vanadium above ground is unused, left in industrial wastes such as mine tailings, debris or steel slags. In fact, a study I published with colleagues last year estimated that 43% of the annual global production of vanadium could be recovered from alkaline wastes, such as steel slag, red mud, fly ashes from coal energy production, and construction and demolition waste.

But there isn’t yet a firmly established technology to recover this vanadium. Certain bacteria and fungi can extract more vanadium from industrial wastes, and various solutions for turning this into useful metal are under development. But we still need to come up with a better way to reach potential sources of this beautiful metal.


Helena I. Gomes, Postdoctoral researcher in Environmental Sciences, University of Hull and Helen Abigail Baxter, Post Doc Research Assistant, Department of Geography Environment and Earth Sciences, University of Hull

This article was originally published on The Conversation. Read the original article.

Wealth in waste? Using industrial leftovers to offset climate emissions

Helena I. Gomes, Mike Rogerson, and Will Mayes.

More than a billion tonnes of potentially toxic, bleach-like waste is produced and piled in landfills every year, with often devastating effects. And yet most people haven’t even heard of these “alkaline wastes”.

We want to change this. Our research has identified nearly two billion tonnes of alkaline residues that are produced in the world each year, most of which can contaminate groundwater and rivers if not proper managed. We should be doing much more about the problem – these wastes can even be put to good use.

Alkaline waste can be solid or sludgy. It mostly involves slags, ashes or muds formed as a byproduct of steel, aluminium or coal power plants, waste incineration or the construction industry. All these wastes are different, but what they have in common is that they rapidly create bleach-like solutions when they meet rainwater.

Steel slag, a byproduct of the steel industry and an example of an alkaline residue.

Often it’s simply stored in piles or sent to landfill. This isn’t safe. The waste can form toxic dust that blows into the atmosphere, while rain that lands on top can filter through, picking up toxic chemicals and producing caustic “leachates” that can flow out into rivers and groundwater.

Steer well clear

Alkaline leachates have a toxic effect on aquatic life (we wouldn’t want to swim through bleach, either). It raises the water pH and metal concentrations, and consumes oxygen.

Carbonate precipitates in a small stream smothers aquatic habitats.

Once this stuff has been produced it’s hard to stop. Steel mills can be a source of alkaline leachates even 30 years or more after closure. Water with pH higher than 12 (somewhere between soapy water and bleach) has now leaked from one chromite waste tip for more than 100 years.

It’s hard to determine the exact link between contamination and problems for plants and animals, but alkaline waste can clearly cause harm. Studies have found ash from coal plants has killed geese and made tree swallows smaller and less fertile.

Perhaps the most severe case of alkaline waste poisoning happened in 2010, when a dam failed at an aluminium refinery in Ajka, Hungary. This released a million cubic metres of “red mud”, a byproduct of aluminium production with a pH level of around 13 in this case – similar to oven cleaner. The red mud inundated 1,000 acres of agricultural and urban land and was transported more than 120km down the Marcal river to the Danube, “extinguishing” all life in the tributary. The flood drowned ten people and left many more with severe chemical burns.

Can we make it stop?

We can treat alkaline leachates through aeration or by adding acid to neutralise it but this is expensive. We need sustainable alternatives. One promising proposal involves constructing wetlands in and around polluted sites, where the marshy ground, the plants and the associated microorganisms restrict the contamination.

Many attempts have been made to find ways of reusing these wastes but none of them are practical enough to stop landfill disposal. Alkaline wastes have been used in road construction, concrete, cement and plasterboard, for example.

Adding these wastes to the soil can reduce acidity, so usage as phosphate fertiliser is also common, while labs are testing whether it can be used in wastewater treatment.

All right junk in all the right places?

It can even help the fight against climate change. Chemicals in the wastes such as calcium and magnesium react with carbon dioxide and remove it from the atmosphere, storing it as a stable mineral. This form of carbon sequestration essentially mimics natural weathering processes and could be a safe and permanent storage option since only acid or extreme temperatures of 900°C or more can release this CO₂. It could even help offset some of the emissions from the energy-intensive industries that create alkaline wastes in the first place.

In fact, if all materials that contain silica (cement, construction and demolition wastes, slag, ash and combustion products) were used for sequestration they could take 697-1,218 megatonnes of CO₂ out of the atmosphere each year.

Steel slags alone could capture 170 megatonnes per year, while the red mud stored worldwide could capture 572 megatonnes. If all the red mud produced in a year was carbonated, 3–4% of the aluminium industry’s global CO₂ emissions could be captured.

Red mud has already sequestered 100 megatonnes of CO₂ worldwide from the late 19th century to 2008 – without the industry even trying. Boosting this number could allow for some real downward pressure on its emissions.

Maybe it’s time to get clever

Recent studies have shown alkaline wastes also contain large quantities of metals we would like to recover for recycling. Some are critical in terms of supply, or essential to new green technologies. For example vanadium, used in offshore wind turbines, lithium and cobalt for vehicle fuel cells, and rare earth elements crucial for solar power systems.

The obvious solution: try to unify the needs of resource recovery and remediation, by developing treatment methods for alkaline leachates that recover critical elements soluble at high pH, suppress dust production, increase carbon sequestration and treat the pollution caused.

With thanks to our study co-authors Douglas Stewart, professor of geo-environmental engineering, and Ian Burke, associate professor of environmental geochemistry, both at the University of Leeds.

To learn more about the Alkaline Remediation project, visit the website: https://alkalineremediation.wordpress.com/ 
 

Helena I. Gomes, Postdoctoral researcher in Environmental Sciences, University of Hull; Mike Rogerson, Senior Lecturer in Earth System Science, University of Hull, and Will Mayes, Senior Lecturer in Environmental Science, University of Hull

 
This article was originally published on The Conversation. Read the original article.

An island apart

by Lindsey Atkinson

Having recently had the good fortune to visit Barbados and some of the Windward Islands in the Lesser Antilles I was struck by the difference between Barbados and the other islands and curious to find out why.  Now you’ll have to excuse me as I am not a geologist so I am wandering into new territory with this blog...

The Windward Islands are the more southerly islands of the Lesser Antilles, including  Martinique, St Lucia, St Vincent and the Grenadines, and Grenada.  They lie near the eastern edge of the Caribbean tectonic plate and are part of the Lesser Antilles volcanic arc.  Being largely volcanic in origin the larger islands are mountainous with a rich volcanic soil and they still have active volcanoes.  Seismic activity in the area is monitored by the University of the West Indies Seismic Research Centre.  

Sulphur springs, La Soufrière, St Lucia

Sulphur springs in La Soufrière, give away St Lucia’s volcanic origins while its namesake, La Soufrière (1234m) on St Vincent, last erupted in 1979 replacing the lake that used to lie in the crater with a lava dome.



Inside the crater, La Soufrière, St Vincent

Barbados stands apart from the other islands being the most easterly of the Caribbean islands, 160km east of St Lucia.  It also differs in being a relatively low lying island, with the highest point at Mount Hillaby (340m), and it differs in origin from its nearest neighbours.


Former coral colonies, Little Bay



Sedimentary layers, Little Bay

Unlike the Windward Islands, Barbados was not formed by volcanic action and it lies at the very edge of the Caribbean tectonic plate.  As the South American plate was subducted under the Caribbean plate sediment was scraped off the South American plate, including deposits of pelagic organisms, forming an accretionary prism.  These layers were subsequently covered by a coral cap.  Both former coral colonies and sedimentary layers  can be seen exposed on the east coast, as here at Little Bay (left).

The movement of the plates resulted in uplifting of these deposits until eventually the island was exposed above sea level.  This happened in stages resulting in ridges which are visible across the island.

Harrison Caves

Little Bay

The island is therefore predominantly limestone, with little surface water as the water filters through the rock.  Beneath the surface are caves such as Harrison Caves with stalactites and stalagmites while on the surface there are dry gullies.  Some of these gullies may have formed when limestone cracked during uplifting or, as in the case of Welchman Hall Gully, where a cave roof has collapsed.  


Erosion has also done its work as the pounding Atlantic waves on the east coast have resulted in the dramatic cliffs of Little Bay and the limestone ‘mushroom’ rocks  of Cattlewash Beach. 

'Mushroom' rock on Cattlewash Beach

And of course erosion of the coral rocks has created the beautiful sandy beaches so beloved of tourists!

Crane Beach, South Coast



Bibliography:

Barbados National Trust   http://barbadosnationaltrust.org 

Donovan SK and Harper DAT (2005) The geology of Barbados: a field guide.

Caribbean Journal of Earth Science 38: 21-33.

Radtke U and Schellmann G (2006) Uplift History along the Clermont Nose Traverse on the West Coast of Barbados during the Last 500,000 Years - Implications for Paleo-Sea Level Reconstructions. Journal of Coastal Research 22: 350-356

Saunders et al. (1984) Stratigraphy of the Late Middle Eocene to Early Oligocene in the Bath Cliff Section, Barbados, West Indies.  Micropaleontology 30: 390-425

The Soufrière Foundation http://www.soufrierefoundation.org/about-soufriere/geology

University of the West Indies Seismic Research Centre http://www.uwiseismic.com/Default.aspx