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SAI INTERNATIONAL SCHOOL
                        STD VII                                                SUBJECT - GEOGRAPHY
                             TOPIC-CH -2- INSIDE OUR EARTH(LESSON NOTES)

            SUB-TOPIC- 2- Igneous rocks
            NOTES-
                 ÿ Mass of mineral matter that makes up the earth's crust is called a rock. It can be of
                     different colour, size and texture.
                 ÿ There are mainly 3 types of rocks. Today we will discuss about the 1st one that is
                     Igneous rock.
              - Ignis is a Latin word meaning fire.
              - They are also called primary rocks.
              - After volcanic eruptions happen, the molten magma comes out of volcano and cools down to

             become solid are called igneous rock.
                 ÿ There are 2 types of igneous rock.
              i) Intrusive rocks
              ii) Extrusive rocks




                ÿ Extrusive rocks- When lava(red fiery molten magma) comes out from the interior of the

                   earth on the surface then lava rapidly cools down and becomes solid.Rocks formed in such
                   a way on the crustare called extrusive rocks.
              - Example- basalt, rhyolite & andesite etc.
              - They have very fine grained.


                ÿ Intrusive rocks- Sometimes the molten magma cools down
            deep inside the earth's crust.Solid rocks formed are called intrusive rocks.
               - Example- granite, diorite & gabbro etc.



            - They cool down slowly thats why they form large grains.
               - Grinding stones used to prepare paste/powder of spices & grains are made up of granite.
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