Inside Our Earth — Social Studies STD 7 — Question

Igneous and Sedimentary rocks changes into metamorphic rocks under heat and pressure. Metamorphic Rocks: When under heat and pressure igneous rocks and sedimentary rocks change their form and more precious rocks are formed to be known as metamorphic rocks.Examples:

• Granite into granite gneiss.
• Coal into slate.
• Slate into schist.
• Limestone into marble.

Limestone is changed into marble due to the following reasons:

• The overlying layers of rocks put pressure on the underlying rocks.
• From surface to interior of the earth, temperature and heat go on increasing.
• Due to pressure and heat, the original limestone changes into marble.