Sifting through the Sands of Time (General Reading)

Sifting through the Sands of Time

When you're on the beach, you're stepping on
ancient mountains, skeletons of marine animals, 
even tiny diamonds. Sand  provides a mineral treasure-trove, a  record  of geology's earth-changing  processes

     Sand: as children we play on it and as adults we relax on it. It is something we complain about when ft gets in our food, and praise when it's moulded into castles. But we don't often look at it,  If we did, we would discover an  account of a geological past and a history of marine life that goes back
thousands and in some cases millions of years. 

     Sand covers not just sea-shores, but also ocean beds, deserts and  mountains.  It is one of the most common  substances on earth, And  it  is a major element in  man-made  materials too - concrete is largely sand, while glass is made of little else.
     What exactly is sand? Well, it is larger than fine dust and smaller than shingle.  In fact,  according to the  most generally accepted scheme of measurement, devised by the Massachusetts Institute of Technology, grains qualify if their diameter is greater than  0.06  of a  millimetre and less than 0.6 of a millimetre.
     Depending on its age and origin, a particular sand can consist of tiny pebbles or porous granules.  Its grains may have the shape of stars or spirals, their edges  lagged or smooth.  They  have  come from  the  erosion  of rocks,  or from the skeletons of marine  organisms, which accumulate  on the bottom  of the oceans, or even from volcanic eruptions.

     Colour is another clue to sand's origins. If it is a dazzling white, its grains may be derived from  nearby coral  outcrops, from crystalline quartz  rocks or from gypsum, like the white sands of New Mexico. On Pacific Islands jet black sands form from volcanic  minerals. Other black beaches are magnetic. Some sand is very recent indeed, as is the case on the island of Kamoama in Hawaii, where a beach was created after a volcanic eruption in 1990, Motten lava spilled into the sea and exploded in glassy droplets.
     Usually, the older the granules, the finer they are and the smoother their edges. The fine, white beaches of northern Scotland, for instance, are recycled from sandstone several hundred million years old. Perhaps they will be stone once more, in another few hundred million. 

     Sand is an irreplaceable industrial ingredient whose uses are legion: but it has one vital function you might never even notice. Sand cushions our land from the sea's impact, and geologists say it often does a better job of protecting our shores than the most advanced coastal technology.

Note:
In this type of task, the questions test your ability to locate the right information in  an  article  or  passage.  When  you  meet  a  set  of short-answer  questions  in IELTS, you should read them carefully, before you go back to the text. In this way, you will know what you are looking for.

1. What TWO substances made, by humans are mentioned in the text?
2. Which part of a grain of sand have scientists measured?
3. What TWO factors determine the shape of a piece of sand?
4. How was the beach on Kamoama Island created?
5. Where, according to the text, can fine sandy beaches be found?
6. Who argues that sand is more efficient than coastal technology?