The Splendor of Sand

Sand in your eyes causes pain, but how soothing it is under your toes! Vast amounts of it are suspended in seawater, but it also abounds in bone-dry deserts. Hordes of creatures flee its encroachment, but for others, it is home. It is often considered a nuisance, but without it, modern living would be nearly impossible.

From the above description, sand seems to be somewhat of a paradox. Just what is sand, and where does it come from?

A Rough Beginning

Sand is composed of particles of minerals, rock, or soil, with quartz being the most common constituent. Peaks that once stood rock solid have eroded into sand. How does such erosion occur?

Sand is often the product of ocean violence. Waves smash against coastal cliffs, and these collisions loosen and rip away slabs of rock. Very large pieces surrender before the unremitting assault, being sloughed off in chunks into the surf. The churning sea grinds off sharp edges, producing boulders. Constant motion gradually wears them into pebbles, and these are crushed into still smaller particles, which we know as sand. Sometimes the sea carries the sand off, but in many places, waves heave the sand back ashore, leaving pristine beaches.

When cold weather combines with ocean violence, frozen water becomes trapped in rock, producing icy wedges that split the stones. The fracturing goes on, reducing large rock masses to smaller and smaller pieces, which eventually become sand.

The wind too plays a role, lifting grains of sand and driving them against rock masses. The abrasion creates more sand. Layers of rock hundreds of feet thick give way before this natural form of sandblasting. Meanwhile, the wind scatters the resulting sand, stretching it out like a carpet on the desert floor.

Over millenniums, these harsh processes have yielded countless tons of sand. Many people would be delighted if it were used only to provide contoured cushions at the beach. But sand's value reaches far beyond the shore, as we shall see.

Tiny Grains, Huge Benefits

To a large degree, our eating and drinking is dependent on sand. How is that? In one way or another, all our food comes from the vegetation of the earth. Sand and its finely ground cousins silt and clay supply minerals that plants need. Also, sand in the soil allows air and water to circulate. Thus, plant roots can easily absorb nutrients. But how is sand involved in quenching our thirst?

If you fill a one-quart (one-liter) jar with dry sand, you can add a third of a quart (300 milliliters) of water to that same jar without making it overflow. This is so because sand is porous-that is, between its grains there is a lot of space. In fact, there are sand "water jars" large enough to supply large cities with the life-giving fluid. What are they?

Geological formations called aquifers lie below much of the earth's surface. Composed of vast layers of sand and other porous minerals, these contain water that has been filtering downward for possibly thousands of years. Scientists calculate that these unseen "water jars" hold 40 times more fresh water than all the lakes and rivers on earth. Wells tap aquifers for their precious liquid, which sustains the lives of millions.

Sand Before Your Eyes

You may be walking on sand every day without ever going to the beach. Are streets or sidewalks in your hometown paved with concrete? In some cases, sand makes up one quarter of this common building material. Hundreds of millions of tons of sand are consumed annually as construction material, so much so that some places have experienced shortages of sand.

While sand generally lies underfoot, in another form it may be right before your eyes. The screen on your computer is likely made from sand, as are the lenses of mountaintop telescopes and desktop microscopes. The same is true of crystal vases and your bathroom mirror. Those items are all made of glass, and sand constitutes over half the raw material that is used in glassmaking. How is sand used to make glass?

Sand and other ingredients are mixed and then melted at temperatures exceeding 2,600 degrees Fahrenheit (1,400°C). The resulting viscous liquid can be rolled, blown, bent, drawn, and spun into almost any form. Glass fibers are even woven into cloth. But whether it promotes beauty or industry, whether it refracts or reflects, smooth, clear glass comes from the opaque grit of sand.

Sand on the Move

Imagine a hill 250 feet high that moves. This happens when piles of sand called dunes migrate, pushed by the wind. In some parts of the Sahara, dunes seem to string out their undulating ridges endlessly.

When humans establish themselves nearby, dunes may pay them an unpleasant visit. Indeed, sand on the move has been known to block highways, swallow houses, and bury entire towns.

Abounding With Life

As lifeless as sand may appear, many creatures call it home. Foxes, snakes, and scorpions burrow in desert sand during the day. Sleeping through the heat, they come out at night to hunt for food. Along Namibia's Skeleton Coast, in southwest Africa, elephants roam the vast dunes. They seem to have fun on the steep, sandy inclines, sliding down dragging their back legs. The "ship of the desert," also known as the camel, cruises the sand seas of Asia and Africa.

Some animals come up out of the ocean to make use of sand. When their biological clocks sound the alarm, horseshoe crabs, sea turtles, and small fish called grunions ride the surf to the shore. There they lay their eggs to incubate in the softness of the sand.

For certain flowers, a dune is as comfortable as a window box. Sea rockets, beach peas, and beach morning glories flourish in sand and push their heads back up even when a dune buries them. Their long roots pull up water and nutrients to feed dainty blossoms-dabs of color on the monotone canvas of sand.

Frankie Goh is a full-time family counselor. He manage and host a website : Earn Money Online http://www.ezy-cash.com
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Using Fresh Air as a Construction Material

Is it possible to create a building with walls and a roof made from 99.5% fresh air? Would it then be possible for this building to withstand anything the weather could throw at it – from gale force winds to heavy snow fall? The surprising answer to these questions is yes! Not only is it possible but it is already being done in many countries around the world. The buildings in question are in fact inflatable buildings.

It’s important at this point to make a distinction between air-supported buildings and inflatable buildings. A traditional air-supported building is one which is comprised of a single layer membrane attached to the ground around its perimeter. Air is blown under the membrane to lift it off the ground and form the shape of the building. An inflatable building on the other hand, uses two layers of membrane connected together typically using spars made from the same material. The cavity formed between the layers is pressurised with air producing a rigid structural element which allows large span structures to be achieved. The key difference between the two styles of building is that air-supported buildings require airlocks at all the access points to prevent air being lost when doors are opened since the entire occupied space of the building is pressurised.

An inflatable building only requires pressurised air within the cavities of the walls and so does not require airlocks since the occupied interior of the building is at normal atmospheric pressure. Since a much lower volume of air is pressurised, inflatable buildings require a lot less power for continuous operation.

The air contained within the walls of an inflatable building become a true structural part of the building. The membranes used in the construction of such buildings are typically less than 1mm thick and so the amount of membrane used compared to the volume of air contained within the walls is incredibly low (typically less than 0.5%).

A major benefit of this style of construction is that air is available just about everywhere on the planet. When a building needs to be moved, the air can simply be allowed to escape enabling an entire building to be packed in to a very small volume compared to its inflated size. The building can then be transported easily to its new location and inflated using the one building material which is readily available everywhere – air! Better still, this building material is absolutely free.

David Kelsall is the technical director of Tectoniks Limited in the UK. He has over 14 years experience in the design of pressurised structures including inflatable buildings, hot-air balloons, airships and pressure vessels. Examples of his work can be found at http://www.tectoniks.com/products.php
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