Please subscribe for the subject to access this lesson.



  1. Definition of Rock
  2. Types of Rock
  3. Mode of Formation of Rock Types
  4. Characteristics of Rock Types
  5. Economic Importance of Rocks to Man


Definition of Rock

A rock is any solid substance that forms part of the earth crust. This solid substance may be hard, like granite or even be soft like mud. In other word, rocks are aggregates of minerals, that is, a combination of different minerals.

The most common rocks and their minerals include;


Types of Rock

There are three major types of rocks according to their origin, mode of formation and physical appearance. They are

1. Igneous Rocks

Mode of Formation

These rocks are formed from the cooling and solidification of molten rock or magma from the earth beneath. They are crystalline in nature. Examples are Basalt and Granite.

Types of Igneous Rocks

Igneous rock could be divided into two, namely: Intrusive or plutonic igneous rock and Extrusive or Volcanic Igneous rock.

(i) Intrusive Igneous Rocks

Intrusive Igneous rocks are rocks which solidified deep in the crust and they are only seen on the surface after a prolong erosive action.

Please subscribe for the subject to access this lesson.
Back to: GEOGRAPHY – SS1 > First Term
© [2020] Spidaworks Digital - All rights reserved.

We are resetting the game!

ClassHall is built on game design principles, and the top performers are the MVPs!

By 11:59 pm Dec. 31st, 2019, we will reset all user performance data, including points and ranks to enable newcomers compete favourably for the limelight!

Prizes will be given to the top 5 MVPs of the Hall of Fame, at the end of the 2019/2020 academic session.

Earn a referral fee per user for recommending us to your students, colleagues and school admins.

Heard of our TRC?

We believe teachers should earn their full reward on earth!

Congratulations to the TOP 5!

Sophia Awhata

Final Points



Senior Prefect

Seun Adeniyi

Final Points




Mary Adebayo

Final Points




Aderonke Babalola

Final Points




Olufunke Fasipe

Final Points




Classhall live video classes


You’re missing out if you haven’t joined our live video classes. NO ADDITIONAL COST if you are on a termly or yearly subscription plan.