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Tracing History With Soil: Often, soil gets deposited in distinct layers. Our activities such as agriculture, landscaping, and construction mean that soils in many locations are constantly mixed and changed in composition. So, to find undisturbed soil, we may have to travel afar, like the upper altitudes of the Nilgiris or the Himalayas. By digging a pit or a trench a few metres deep in these sites, you can reach soils that are over 45,000 years old! Every few centimetres you dig, you can reach back in time, and if you’re lucky, you may find well-preserved pollen grains and fossils, that can give us a lot of information about the plants, animals, and how the climate was all those years ago! For example scientists can find out what kinds of grasses, trees were present 10,000 years ago, and if the weather was predominately wet or dry and if there were a lot of fires – charcoal in the soil layer can give us this information.
Soils are formed from rock. These rocks can be millions of years old. Maybe you have stood on some of these rocks yourself. So, the soil close to the surface that we see today can be really old as well – anything from a few thousand years old to over a million years old! The grinding action of moving glaciers, erosion by wind, flowing or continuously falling water, can all contribute to the making of soil from rock. Soils not only contain mineral matter from the breakdown of parent rocks, but also organic matter, that is dead and decaying organisms. Sometimes, soils are formed in one place and the particles are transported by water and wind to another.
The Colours of Soil: If you’ve ever taken a long journey by road or rail, you may have seen the colour of soil change from place to place. Brown, yellow, red, even black. What is the colour of soil around your home, in your school? Can you remember where you have seen different colours of soil? Write to us and tell us about it at firstname.lastname@example.org
Write to us at email@example.com with the results of your experiment with soil and coloured water and your drawings and descriptions from your field diary of creatures you found in soil for a chance to win a book on life in soils. Were you able to identify all the creatures in the soil?