The Archaean Formations or Pre Cambrian Era : The first ever topic that appear when we start reading geography for upsc and start reading the Geography of India by Majid Hussain or any other high level competitive examinations is the structure of India and we will going to discuss this topic summary pointwise to make your point clear for preparations.

Point Wise Summary of The Archaean Formations :

• The term archaean was first introduced by J.D Dana in 1872
• Archaean means the oldest rocks of earth’s surface.
• Pre Cambrian Constitute about 86.7% of World history.
• First photosynthesis, chemosynthesis and life supporting earth’s atmosphere formed during this year.
• Archaean Rocks are foundation for all great plateaus and mountains ranges.

Characteristics Of Rocks & Minerals found in them :

• Rocks are extremely crystalline, contarted, and faulted without any sediments.
• Rocks are reach in Iron ore, copper, manganese, Mica, Zinc, and Gold.

Types Of Rocks :

1. The Bengal Gneiss :-

These rocks first found in Mindanpur district of West Bengal , These types of rocks have lots of layers and they mainly found in Eastern Ghats, Odisha, Manubhum & Hazaribagh district of Jharkhand, Nellore Andhra Pradesh, Tamil Nadu, Son Valley and Mikir Hills.

2. The Bundelkhand Gneiss :-

These rocks are forms of massive granitoid, it mainly found in bundelkhand, bhagelkhand, Maharashtra, Tamilnadu & Andhra Pradesh.

3. The Nilgiri Gneiss :-

Rocks of nilgiri gneiss are dark coloured & blueish grey, it mainly found in Nilgiri, South Arcot, Palni hills, Shevaroy hills, Nellore in andhra pradesh, Balasore in orissa,Karnataka kerala,malabar, jharkhand & chhattisgarh.

This was all about the The Archaean Formations or Pre Cambrian Era , keep looking our GEOGRAPHY section for all topics summary, if you have any suggestions comment in box.