Why Don’t All Beaches Have Traditional Yellow Sand?

Aleksandra Nikoniuk

When choosing a summer holiday destination we often find ourselves looking at different beaches. Some of you might have noticed that they come in a variety of colours. And it doesn’t depend on their geographical  location. Look at Greece. There are plenty of beautiful, white or yellow sand on the shore of Greek islands, but you can find black beaches there too! Why is this so?

It all starts with the process of sand formation. It is made from rock and minerals, which are subject to destruction through mechanical or chemical erosion, abrasion and extreme changes of temperatures. All these processes break down rocks into smaller fragments, which are transported via wind and water (e.g. rivers, rainfall) towards the sea. The most common types of rock are made up of silica and calcium carbonate.

All the sand in the world is made in the same way. So why can it be so different? It’s because there are various kinds of minerals that contribute to the formation of rock. So different minerals found in given areas affect the colour of the sand.

Let’s look at the standard, yellow-coloured beaches, which can be found in Southern Europe. Their sand is formed of quartz, which contains traces of iron that give the yellow colour. Quartz without those impurities forms white sand. This is common in beaches in tropical regions such as Cape Santa Maria in the Bahamas or those beaches found on Caribbean Islands.  This colour is also the result of mollusk shells and corals, whose white colour contributes to the clear white colour of the beach.

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Image Credit: Public Domain Pictures

However, beaches can look a bit more extraordinary. Those located near volcanic deposits can display a variety of colours, mainly black, which is caused by the presence of basalt. Basalt is a rock which forms when water meets hot lava. It then cools down and breaks into small pieces. One of those beaches can be found in Iceland and was once placed in the top ten most beautiful beaches in the world. Black sand is also the results of placer deposit formation, which is an accumulation of the various minerals found at the bottoms of rivers and lakes. They can contain more valuable minerals such as sapphire, gold or even diamonds.

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Image Credit: Wikimedia Commons

Some very strange beaches can be found in Hawaii. Apart from the volcanic ones, red or even green sand can be found there. The former is caused by the excess of iron and is present at the Maui island, the latter by the the mineral olivine near Papakolea Beach. California boast purple beaches, for example Pfeiffer beach. Its colour is caused by another manganese garnet from the surrounding area.

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Image Credit: Wikimedia Commons

One of the most mesmerizing beaches in the world is a pink beach found in Bahamas. Similarly coloured sand can be found elsewhere, typically near coral reefs. One of the organisms living in the reef is red and when it dies it falls to the bottom of the ocean. The waves move it to the shore and its small particles mix with the sand resulting in beautiful light pink shade of the sand.

If all those minerals have such an impact on the colour of the sand there must a place where there is more than one odd colour present. Rocks where the minerals are mixed, such  as those formed in an Ice Age can produce multiple different coloration of the beach. That is the case at The Rainbow Beach in Fraser Island in Australia, where one can see even 70 colours displayed on the sand.

 

The Autumnal Rainbow: Why Do Leaves Go Different Colours?

Aleksandra Nikoniuk

It’s here again; the most colourful season of the year. While walking down the street you might wonder why green leaves, which surround us in the summer, suddenly change their colours. Why do they go through all the hassle of displaying such a variety of shades and tones when it seems much easier to just turn brown and fall off the tree straight away?

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Image Credit: Pexels

The answer is in the pigments that can be found in a leaf. You’ve probably heard of chlorophyll, a pigment present in all green plants, which is responsible for the production of energy. It absorbs solar rays and turns them into sugars, which allow plants to grow.

Large quantities of chlorophyll are present in many chloroplasts across a plant, which causes their green colour. However, there are other pigments as well, such as carotenoids. During spring and summer, the amount of chlorophyll is so great that it masks the effect of other pigments. When chlorophyll is not being replenished anymore, the amazing shades of yellow and orange are revealed.

Let me explain how it all works in a bit more detail:

During energy production chlorophyll is broken down. However, the veins of the leaf (which you can easily spot on its surface) provide essential nutrients for the chlorophyll to be synthesized. So during spring and summer when days are long and nutrients are readily available, chlorophyll production can continue.

As the days get shorter and nutrients more scarce those veins are closed off and as a result chlorophyll can’t be replenished anymore. This is when different coloration by other pigments in plant cells becomes visible.

Carotenoids are the second largest group of pigments (after chlorophyll) and are responsible for the yellow and orange colour of the leaves in autumn. You can also see them all year around in fruits and vegetables such as carrots or bananas.

The red colours of the autumnal leaves are caused by another kind of pigment called anthocyanins. Contrary to carotenoids they are not always present in the leaves and are produced only at a specific time of the year. The production of anthocyanins begins when the important nutrients such as phosphate, responsible for the breakdown of sugars produced by chlorophyll, stop reaching the leaves and concentrate in the stem of the plant instead.

That change in the sugar breakdown process triggers the production of anthocyanins. Interestingly, the weather influences the intensity of the pigment produced. The synthesis of red pigments begins in late summer and sunny weather during that period of time increases the intensity of the colour. Additionally, cool and bright autumn, with little rain and no frost greatly enhances the shades of anthocyanins.

Anthocyanins are synthesized in addition to existing pigments, so what could their function be? It has been suggested that the change of leaf colour could be a form of protection against parasites. There’s some evidence that the red colour of anthocyanins can scare off potential parasites, who would use that tree as a host, as it signals the presence of a toxic substance on that tree.

Unfortunately, we can only enjoy beautiful autumnal colours for a few weeks. Since the production of chlorophyll slowly ceases, an extra layer forms on the surface of the leaves and gradually limits the flow of nutrients.

By late autumn this prevents anything from being transported and a leaf falls off. So let’s enjoy the autumnal landscape while we still can.