Place the clay balls close together on a piece of waxed pager. Place a second sheet ofwaxed paper on top of the clay balls. Now, put stack some books on top of the waxed paper. Imagine that the books are layers of rock building up on top of the rock particles. The pressure of the rock particles increases as you add each book.
Heat builds as the rock particles are pushed deeper into the Earth's crust.
Now remove the books and peel away the waxed paper. Look at the clay. An entirely new kind of rock has been formed. The same thing happens to igneous and sedimentary rocks when they are changed. Igneous Igneous rock was once hot liquid inside the earth.