Page 218 - New Medley 5 Semester 2

Sedimentary rocks

For millions of years, small pieces of our earth have been eroded, broken down

and worn away by wind and water. ese pieces were washed downstream where

they settled at the bottom of the rivers, lakes and oceans. Layer a er layer of

eroded earth pieces were deposited and got compressed with time, until the

bottom layers turned into hard rocks. ese rocks are called sedimentary rocks.

erefore, sedimentary rocks are found in layers which are formed by the
sedimentation of eroded earth pieces.
• Hands-on Learning
S E
L
Activity Self-Management
Can you guess what was the cementing material of eroded earth pieces?
1. Mix 1 cup of water and ½ cup of epsom salt (hydrated magnesium sulphate) in a bowl. Stir
until most of the salt dissolves.
2. Place about 1 inch of sand in a small paper cup. Add enough salt solution to just cover the
sand and then mix well. Let the mixture stand until dry (it will take about 2 to 3 days).
3. Cut off the paper cup and take a closer look at the rock. Where is the salt? How does it hold
the sand together?

In the same manner, layers of eroded pieces of the earth were held together by

minerals.

ere are many kinds of sedimentary rocks.

 Sandstone rocks: ese are formed from small

grains of quartz and feldspar. ese are so and
either yellow, brown, red or pink in colour.

Sandstone is mostly used as building stone. e
Red Fort in Delhi is made of red sandstone. Red Fort, Delhi

 Limestone rocks: ese are formed from a mineral called calcite. Calcite
generally comes from the beds of evaporated seas and lakes, and from the
shells of sea animals. Limestone is used in the manufacture of concrete and

is an excellent building stone for humid regions. e chalk used for writing
on blackboards is also made from limestone. It is also used for making glass.

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