History of Science

Dear Readers!

Christmas is almost upon us and so at Four Degrees we decided to devote our next post in the ‘What’s Geology got to do with it?’ series to Christmas! Marion and I have selected varying aspects of the festive season from trees to biblical stories and common Christmas presents, and linked them to geology (some tenuous, some not so tenuous…). We hope you enjoy!

The Journey to Bethlehem

The story of Joseph and Mary’s hallowed journey from Nazareth to Bethlehem is an intrinsic part of christmas festivities. But what route did they take and what landscapes would they have seen?

Map of the Holy Land showing the Old Kingdoms of Judea and Israel drawn in 1759. Source – Wikimedia Commons

As a distinct geographic area, the description “Holy Land” encompasses modern-day Israel, the Palestinian territories, Jordan and sometimes Syria. The geology of the Holy Land is characterised by the Judean Hills which run North to South through the centre of the region exposing Cretaceous age limestones and sandstones. The rocks reach down to the western banks of the Dead Sea and the Jordan Valley Rift valley which marks the modern border between Palestine and Jordan. The Judean Hills mark the highest area in the region (an area Joseph and Mary may have been trying to avoid!) and the topography then lowers to the Mediterranean coast to the west and the Dead Sea to the east.

Joseph and Mary’s journey to Bethlehem began in Nazareth in modern day Israel and ended in a manger in Bethlehem, which is in modern day Palestine. The route taken between the two, and indeed the time it took them is oft disputed. Given the mountainous nature of the central Holyland which is dominated by the Judean Hills and the reality of transporting a pregnant woman on a donkey, it is possible they would have avoided the mountains and travelled southeast across the Jezreel Valley, connecting with the Jordan Valley to the East, down to Jericho and then across to Bethlehem. This route would have looked something like this.

Image of the Judean Hill taken in 1917. Source – Wikimedia Commons

The area they may have wanted to avoid, the Judean Hills, is formed from monoclinic folds and relates to the Syrian Arc belt of anticlinal folding in the region that began in the Late Cretaceous. These are the same hills that include the famous Mount of Olives, and the location of the story of David and Goliath which occurred in the Ella Valley in the Judean Hills’. It is also home to Bethlehem which stands at an elevation of about 775 meters and is situated on the southern portion in the Judean Hills.

By contrast, the Jordan valley encompasses the lowest point in the world, the Dead Sea (sitting at 420 below sea level). The valley was formed in the Miocene (23.8 – 5.3 Myr) when the Arabian tectonic plate moved away from Africa. The plate boundary which extends through the valley (and houses the Dead Sea!) is called the Dead Sea Transform. This boundary separates the Arabian plate from the African plate. For more on the geology of the Dead Sea region see this earlier Four Degrees post.

Lego

Christmas tree made of Lego at St Pancras Station! Source – Wikimedia Commons

As children (or adults!) many of us will have experienced unwrapping various Lego sets on Christmas Day. Its popularity has been sustained over the last 50-60 years whilst the company has continued to grow; Lego never goes out of style! But did you know that Lego has been manufacturing its hugely successful interlocking toy bricks since 1949 and as of 2013, 560 billion Lego parts have been produced! But what does any of this have to do with geology?

Lego blocks! Source – Wikimedia Commons

Well, Lego started off as wooden blocks and toys in the workshop of inventor Ole Kirk Christiansen, before moving onto manufacuring the blocks out of cellulose acetate. But since 1963 the blocks have been made from a resilient plastic called acrylonitrile butadiene styrene (ABS). As with many plastics, the Butadiene and Styrene components of ABS are formed from a process that begins with the extraction and cracking of crude oil. Oil consists of a mixture of hundreds of different hydrocarbons containing any number of carbon atoms from 1-100. Butadiene is a petroleum hydrocarbon that is obtained from the C4 fraction of steam cracking (more on steam cracking here ) and styrene is made by the dehydrogenation of ethylbenzene, a hydrocarbon obtained in the reaction of ethylene and benzene. Lego is just another manufactured product who’s journey began in the rocks!

Wrapping Paper

Christmas wrapping paper! Source – Wikimedia Commons

The use of wrapping paper was first documented in ancient China where it was invented in 2nd century BC but it was the innovations of Rollie and Joyce Hall, the founders of Hallmark Cards that helped popularise the idea of wrapping in the 20th Century. Wrapping paper is made using specially milled wood pulp, this pulp is made from a special class of trees called softwoods. The paper is then bleached and decoration and colours are printed onto the paper using dyes and pigments.

Whilst many dyes that are used in the modern day are synthetic, originally all dye materials were sourced from natural materials. Here we focus on how to make the dyes and pigments for christmassy colours!

Powdered Alizarin dye. Source – Wikimedia Commons

There are a variety of natural materials that can be used to make red dyes including lichen, henna and Madder. Madder, made from the dye plant Rubia tinctorum, has been used as a dye as far back as 1500BC it was even found in the tomb of Tutankhamun. Madder was also used to make Alizarin, the compound 1,2-dihydroxy-9,10-anthracenedione. Alizarin was a prominent red dye until synthetic Alizarin was successfully duplicated in 1869 when German chemists Carl Graebe and Carl Liebermann found a way to produce alizarin from anthracene. A later discovery that anthracene could be abstracted from coal tar further advanced the importance and affordability of alizarin as a synthetic dye. This reduced cost caused the market for madder to collapse almost overnight. While alizarin has been largely replaced by more light-resistant pigmens it is still used in some printing. (QI – it is also used in classrooms as a stain to indicate the calcium carbonate minerals, calcite and aragonite!)

Other more exotic inks and pigments used in wrapping paper such as metallic pigments are also made through mined raw materials. To produce metallic pigments, materials such as Aluminium powder (aluminium bronze) and copper-zinc alloy powder (gold bronze) are used to produce novel silver and gold inks!

Christmas Trees

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Abies Nordmanniana on sale as christmas trees. Source – Wikimedia Commons

Christmas trees are an iconic part of Christmas, whether at home or in your local area its hard to go far in December without seeing one most days! In fact they are so popular now that Christmas trees are farmed specifically for this purpose. While the best selling trees in North America are Scots Pine, Douglas-fir and noble fir, in the UK, Nordmann fir is the most popular species due to its low needle drop feature.

As with all crops, Christmas trees require a specific set of nutrients to thrive and these are provided by fertile soil which is controlled by the underlying geology. Elements that are required for health growth include Nitrogen, Phosphorus, Potassium, Calcium, Magnesium, Sulphur, Boron, Copper, Manganese, Molybdenum, Iron and Zinc which are all obtained from the soil.

Where this isn’t available or in areas of intensive farming these elements are derived through the use of fertiliser which relies on mined phosphate for mass production (more on the link between fertiliser and mined phosphate reserves here). In terms of soil types, pine trees are usually better adapted to a sandy or sandy loam soil, while White Spruce trees and fir trees, prefer fine-texture loams and clay loam soils.

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Abies nordmanniana trees located in the Black Sea region of Turkey. Source – Wikimedia Commons

The popular Nordmann fir used in the UK, or ‘Abies nordmanniana’ is native to the mountains to the east and west of the Black Sea in an area which covers Turkey, Georgia, Russian Caucasus and Armenia. They grow at high altitudes of 900-2200 m on mountains and require plenty of rainfall (~1000mm).

The distribution of the species around the Black Sea and its absence in other local areas of similar, suitable climate is thought to be due to the forest refugia that formed during the ice age. Refugia is the term used to describe a location of an isolated or relict species population. This can be due to climatic changes, as with Nordmann Fir, geography (and therefore geology) or human activities such as deforestation. The forest refugia that caused the limited spread of the Nordmann Fir was caused by the glacial coverage during the Ice Age in the eastern and southern black sea which cut off many areas restricting the spread of the species. Indeed the presence of these refugia is the reason many forest tree populations survived at all!

Stay tuned for Marion’s Part 2 of the Christmas Post next week…

Flo

I first came across the intriguing world of nanoparticles when I saw an awe-inspiring talk by nano-extraordinaire Professor Michael Hochella from Virginia Tech at the Geological Society. He wove a fascinating tale about the world at nanoscale, the special properties, the infinite uses and the potential environmental impacts as well as outlining the need for caution, scrutiny and intensive research from the scientific community in the wake of an exploding nanotechnology industry. I’ve decided to re-visit the area of nanoscience for the ‘Momentous Discoveries in Geology’ blog festival.

What’s so special about Nanoparticles?

Solutions of gold nanoparticles of various sizes. The size difference causes the difference in colors. Source – Aleksander Kondinski, Wikimedia Commons.

Nanoparticles refer to particles between 1 and 100 nanometers in size and can be found in nature, inadvertently produced by humans or most recently, manufactured as part of the boom in nanotechnology. Their geo-relevance comes from both their behaviour in nature and potential nanotoxicity but also in their manufacture for engineering processes such as environmental tracers and remediation materials. Nanoparticles are unique and special in their physical properties, which can vary greatly from macro-scale properties. Nanotechnology exploits these unusual properties to improve the efficiency and sustainability of already existing processes. They are highly mobile, have enormous specific surface areas, unexpected optical properties and can exhibit what are known as quantum effects. An example being: superparamagnetism (magnetization that can randomly flip direction under the influence of temperature) a characteristic found in ferromagnetic materials smaller than 10nm. Nanoparticles can also have unusual optical properties: gold nanoparticles for example appear deep red to black in solution, depending on their size. They also melt at much lower temperatures (~300 °C for 2.5 nm size) than gold slabs (1064 °C). Their first known use for their colour-changing properties was back in roman times (30BC – 640AD), using gold nanoparticles, which were impregnated into the glass of

The Lycurgus Cup – a 4th-century Roman glass cage cup , which shows a different colour depending on whether or not light is passing through it; red when lit from behind and green when lit from in front due to the incorporation of nanoparticles – You can go and see it in the British Museum! Source – Johnbod, Wikimedia Commons.

goblets to give a colour change from green to blood red when lit from behind. The requirement of the exact mixture of sizes to manifest this effect suggested that the Romans knew what they were doing!

Early history of nanoparticles

The discovery of nanoparticles has not so much happened as a single momentous discovery but as a series of moments over a ~100 year period. As with many discoveries, they are as a result of breakthroughs in instrumentation and technology which breakdown the barrier to discovery. In addition to the early use in roman times, nanoparticles were also used in the medieval (500-1450AD) and renaissance (1450-1600 AD) periods, again for their colour-changing properties for use in stained glass windows in medieval times and for colouring ceramics during the renaissance. The deep reds you see are caused by the incorporation of gold nanoparticles in the glass and the deep yellows are caused by silver nanoparticles. We also see this effect used in Ceramics. In the Islamic world, where the incorporation of gold in artistic representations was not allowed, the solution was using dense nanoparticulated layers of glaze to generate a golden metallic shine. This colour changing capacity is caused by the size of the materials that are incorporated. Photography is also an early example of nanotechnology which is reliant on the production of silvernanoparticles that are sensitive to light.

When were they discovered?

Michael Faraday – 1861. He first described the optical properties of gold nanoparticles in his classic 1857 paper. Source – Wikimedia Commons.

The earliest and most significant breakthrough came during Michael Faraday’s pioneering experiments and his seminal paper in 1857 where he described the optical properties of nanometer-scale metals for the first time. He prepared the first metallic colloids (fine particles that suspend in solution, in between dissolved and settling particles, size range between 2-500 nm). He saw that they had special electronic and optical properties and stated – “It is well known that when thin leaves of gold or silver are mounted upon glass and heated to a temperature which is well below a red heat (~500 °C), a remarkable change of properties takes place, whereby the continuity of the metallic film is destroyed. The result is that white light is now freely transmitted, reflection is correspondingly diminished, while the electrical resistivity is enormously increased.”.

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First Electron Microscope with resolving power higher than that of a light Microscope designed by Ernst Ruska in 1931 with a magnification of around 12,000 times. Source – J Brew, Wikimedia Commons

While the unusual and fascinating properties of nanoparticles had been described, they were still too small to be seen and it took another 84 long years before electrical engineer Max Knott and physicist Ernst Ruska constructed the prototype electron microscope in 1931. This breakthrough put a spotlight on the “small world” and was an important step in allowing research at the nanoscale. This was followed by Erwin Mueller’s field-ion microscope which allowed the viewer, for the first time in history to observe individual atoms and their arrangement on a surface. This was a landmark invention allowing magnification of more than 2 million times. These technological developments formed the foundation for many other nano breakthroughs to come such as the ‘tunneling phenomenon’, the development of the field of molecular electronics, the development of Surface Enhanced Raman Spectroscopy (SERS), instrumental in the field of nanotechnology, the buckyball, quantum dots (which have implications for how solar energy is collected) and carbon nanotubes.

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This post is for a geoscience blog carnival called The Accretionary Wedge, which is being hosted by Matt Herod and you can see the call for posts here.