Understand how soil is formed, visualize its profile, and distinguish the characteristics of Alluvial and Black soils.
Factors of soil formation.
Soil is the most important natural resource on Earth. It acts as the primary medium for plant growth and supports various types of living organisms.
However, it is a painstakingly slow process: it takes millions of years to form soil up to just a few centimeters in depth.
Diagram of the layers of soil.

The Soil Profile: A vertical section through different layers of the soil.
Fill in the blank for soil layers.
The soil is a living system that takes millions of years to form, with its uppermost layer known as the . The layer just beneath the top soil is called the , which contains weathered rocks, sand, and silt clay. Below that is the consisting of weathered parent rock material. Resting at the very bottom of the soil profile is the unweathered parent . Beyond the profile layers, soils in India are classified into different types, such as the widely spread soil found in the northern plains. According to age, the older alluvial soil with a higher concentration of kanker nodules is known as . Conversely, the new alluvial soil, which is more fertile and has finer particles, is called . Another major classification is the soil, also known as regur, which is ideal for growing cotton.
Properties and spread of alluvial soil.
Alluvial soil is the most widely spread and important soil in India. In fact, the entire northern plains are made of this highly fertile soil.
It has been deposited over thousands of years by three important Himalayan river systems: the Indus, the Ganga, and the Brahmaputra.
Two types of alluvial soil found in the Northern Plains.
New Alluvial Soil
Old Alluvial Soil
Properties and spread of black cotton soil.
Black soils are dark in color and are commonly known as regur soils. They are considered the ideal soil type for growing cotton, which is why they are frequently called "black cotton soil."
Distribution of soil types

Major soil types in India