Six Things About Sand
One of my very favourite places is the beach. I love the sound of the water, the light breeze that always seems to be blowing, the call of the seagulls, and the feel of the sand (except when it gets into unmentionable places!) We have a very nice beach right here in the town where I live (although, unfortunately, the water isn’t always suitable for swimming), and I try to get there at least once a week during the summer.
If you stare long enough at the sand around you on a beach, you quickly become aware of just how much of it there is. Pick up a handful and let it flow between your fingers – thousands and thousands of grains will fall back onto the beach – far too many to count.
1. What Is Sand?
Sand is comprised primarily of silica (silicon dioxide, SiO2) – the second most common (at 25% by mass) element in the earth’s crust (after oxygen). Inland continental and non-tropical coastal (beach) sand comes primarily from quartz that has been pounded by waves and/or wind; tropical and subtropical white sand is eroded limestone with a touch of coral and shell fragments (and bits of other organic material); the sand dunes of White Sands National Monument in New Mexico are composed of gypsum. Sand may contain minerals like magnetite, chlorite, glauconite, or volcanic basalts and obsidian, and occasionally trace amounts of minerals, or even gemstones. ‘Commercial’ sand comes from quarries.
2. How Much Sand Is There In The World?
According to a study from the University of Hawaii, there are (approximately) seven quintrillion five quadrillion grains of sand on all the beaches in the world (that’s a 75 with 17 zeros behind it; i.e., 7,500,000,000,000,000,000). NOTE: if you think that’s a big number, consider that astronomers have postulated that there are 100 stars in the Universe for every grain of sand on the Earth’s beaches (that’s assuming our own Milky Way galaxy, with its hundreds of billions of stars, is ‘typical’, and that the Hubble space telescope is correct in its estimate that there are at least 80 billion galaxies in the world). The next time you’re on the beach, run those numbers through your head – it sort of makes our little planet (and us) seem pretty insignificant, doesn’t it?
3. What Is Sand Used For?
There are almost as many uses for sand as there are types of the stuff. It is commonly used in agriculture, landscape and building materials (including concrete, bricks, glass, and even some paints), aquariums and artificial reefs, beaches (a lot of sand on ‘popular’ beaches is imported), to fill ‘sandbags’ to hold back water during flooding, to provide traction on roads when things get slippery, in the casting of parts in manufacturing, and for sandblasting and etching. Probably the most common use for sand is the manufacture of computer chips (they don’t call it ‘Silicon Valley’ for nothing). NOTE: for a fascinating look at how they turn sand into a computer chip, check out this page from Intel.
4. When Sand Sings
One of the strangest anomalies around sand is the ‘singing sands’ phenomenon. This has been observed in several deserts (‘singing sand dunes’) as well as on some beaches (including two right here in Canada – one in Ontario’s Bruce Peninsula , and one on Prince Edward Island). In order for sound to be emitted from the sand, it’s agreed that (1) all the grains have to be round and between .1 and .5 mm in diameter, (2) the sand has to contain silica, and (3) the sand must be at a certain humidity. The most common frequency for the sounds emitted (often heard as a haunting hum, but sometimes a booming or roaring) is about 450 Hz (the sound of a typical car horn). There are plenty of hypotheses regarding what causes the sounds (friction between the grains, compression of air between them, resonance between the dry surface layer of the sand and the moist ground around it) but scientists really can’t explain it. Personally, I think it’s just one more really cool thing about sand!
5. Sculpting with Sand
Who hasn’t built a sandcastle at some point in their lives? Either in a sandbox or on the beach, sandcastles are a great way to liberate your inner architect, and construct the ‘house of your dreams’. The process of sandcastle building can be fun, or serious, and anyone can do it (although there are some people who take it VERY seriously –sand sculpting competitions are popular the world over, and professionals produce sculptures that are unbelievably realistic or outrageously fantastic). In order to build a ‘perfect’ sandcastle (i.e., one that holds together), the right amount of water is needed (the recommendation is 8 parts dry sand to 1 part water). The water acts as a ‘bridge’ between the grains of sand, creating surface tension; if you use too much water, it will fill the gaps between the grains; not enough and they won’t stick together. If you are worried about something, simply head to the beach and build yourself a sandcastle (it doesn’t have to be elaborate), then put your troubles inside and watch as the water washes them all away!
6. The Sands of Time
Most people are familiar with the hourglass – two glass bulbs joined by the thinnest of passages for sand to trickle through, marking the passage of time (i.e., when all the sand from the top has flowed into the bottom, ‘time’s up’). Hourglasses can be used to measure minutes (e.g., the modern-day three-minute egg timer), or, more commonly, hours (from whence it gets its name). Factors affecting the amount of time measured include the amount of sand, the size of the bulbs, the width of the neck, and the quality of the sand. It’s believed the hourglass originated in medieval England (long before mechanical clocks, but after the water clocks that were used in Egypt), and they were used extensively during the early days of oceanic exploration (water clocks were affected by the motion of the boat, sand clocks were not). Of course, the hourglass is often used as a metaphor to suggest that one’s existence is fleeting – that the ‘sands of time’ will eventually run out for every person.
I suppose that’s true – I do know that a great deal of sand has flowed past me on my way to … the other side of 55.