Rocks and Soil
Category : 4th Class
LEARNING OBJECTIVES
This lesson will help you to:—
Historical Preview
QUICK CONCEPT REVIEW
Why are we studying about rocks?
If we took all the rocks away, we would have a miserable life. We use rocks for roads, metals, jewelry, tombstones, building materials, cosmetics, and many, many more things. Most of the famous sculptures of the world are made from blocks of stones such as granite and marble. Did you know that the Great Wall of China and the Taj Mahal are made out of rocks? If we did not have rocks, this earth mould be pretty empty. We can also collect rocks as a hobby.
Amazing Facts
Soil has its own colour palette. Soil comes in: red, yellow, black, brown, grey, and white.
FUN TRICKS
Shortcut to problem solving
Think of a chocolate chip cookie as a rock. The cookie is made of flour, butter, sugar & chocolate. The cookie is like a rock and the flour, butter, sugar & chocolate are like minerals. All rocks are made of minerals
How are rocks formed?
Different types of rocks are formed in different ways.
Granite, basalt are examples of igneous rocks.
Examples of sedimentary rocks include sandstone, shale, and chalk.
Examples of metamorphic rocks include marble, quartzite and slate.
USES OF ROCKS
Rocks have been used by human beings for millions of years. Rocks are used for making tools and weapons and various construction materials. Man gets metals from rocks and makes them into jewelry. Rocks are also used for building roads and bridges.
Misconcept/Concept
Misconcept: All rocks are the same, and it’s hard to tell how they originated.
Concept: Rocks can be distinguished in different types, based on their origins and composition.
Misconcept: Rocks are dull and unattractive
Concept: Beautiful gemstones and precious metals are also derived from rocks.
Misconcept: Soil and dirt are the same.
Concept: While soil can germinate plants. Dirt is dead and cannot germinate plants.
The Importance of Rocks and Minerals
Name |
Type of Rock |
Use |
Basalt |
Igneous |
Used in road building. |
Calcite |
Mineral |
Used in cements and mortars. |
Granite |
Igneous |
Used for buildings, monuments, and tombstones |
Marble |
Metamorphic |
Used in building, floors, tile in bathrooms. |
Obsidian |
Igneous |
Used In making arrowheads |
Pumice |
Igneous |
Used in scouring, scrubbing and polishing materials |
Quartz |
Mineral |
Used in making glass, electrical components, and optical lenses. |
Sandstone |
Sedimentary |
Used in the building industry for house. |
Slate |
Metamorphic |
Used for roofs, chalk-boards. |
WHAT IS SOIL?
Soil is the top layer of the earth's surface, like icing o a cake. In our garden's backyard, we play on grass and soil. Soil is made from rocks that are broken into tiny pieces. It is a mixture of rock particles, as well as organic matter like dead leaves, animal manure, roots, twigs, dead bugs and many insects and worms. Soil is often called the "living skin" of the earth. It is capable of supporting plant life and is vital to life on earth.
TYPES OF SOIL
Humus-rich soil |
Sandy soil |
Clay soil |
Humus-rich soil is able to hold plenty of water, and is also full of nutrients. |
Sandy soil drains water. |
Clay soil can also hold lot of water and tends to be thick and heavy when wet. |
This allows the growth of a wide range of plants. Supports different kinds of insects and animals. |
This allows the growth of desert plants which require less water. |
Certain kinds of plants. Like certain species of grasses, sunflowers, can grow well in clay soil. |
This soil tends to be dark in colour. |
Sandy soil tends to be loose, dry and light brown. |
Clay soil usually contains a high percentage of mineral in the soil, often causing clay soil to be dark red in colur. |
It can be found in forests. |
Sandy soil can be found in drier areas like deserts. |
It can be found in hilly regions. |
LAYERS OF SOIL
Soil is made up of distinct layers. Each layer of the soil is called horizon.
The soil can be divided into four main layers: topsoil, subsoil, parent material and bedrock. Topsoil contains the most humus, which is the dark part of the soil that is rich in nutrients. This layer is made up of minerals and decomposed organic matter and it is also very dark in colour. This is the layer where roots of many plants grow.
Under the topsail are several layers that make up the subsoil. These layers tend to be sandier, and have less humus. Under the subsoil is parent material. Under parent material lays bedrock, which is solid rock. Plant roots are not found in this layer.
SOIL EROSION
Soil erosion refers to the erosion and degradation of land as a result of human activities. It is a major issue that affects the natural environment and agriculture. Soil erosion leads to washing away of top soil, poor drainage and huge organic loss in the soil.
DEFORESTATION
Deforestation is when humans remove or clear large areas of forest lands for agriculture or residential purposes. Cutting down of forest leads to soil erosion and increase in temperature. About half of world's original forests had been destroyed and millions of animals and living things have become endangered due to deforestation.
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