Earth force In the core   When you start to dig a whole (about one hundred meters deep) the first depths are cool but after about thousand meter you will feel that the Earth become warm. While you keep digging you will discover that the Earth is more warmer. Scientists discovered that the outer layer of the Earth is built of solid rock. There are testimonies down to a depth of about eight kilometers (five miles). Scientists can see enter the Earth by mine shifts and holes in the surface of the earth. Consequently, if you can not dig any more do not worry! No one can.Scientist know that the crust of the earth is a solid outer layer with about seventy kilometers (forty- four miles) deep at thickest parts and about three kilometers (six miles) in oceanic  floor as thinnest parts.Mantle is under the crust and it is a layer of pasty rock. Last and  deepest layer of the Earth is the core that scholars said is made of nickel  and solid iron.If you wear a tight body suit after a minute you will feel so hot due to greatly pressure, effected on your body. So the mantle has  a heavy and huge bodysuit about seventy kilometers thick. There is great pressure and hotness in the mantle.  Because of the push and pull forces and high temperature some of the mantle it is melt manner but most of them, over 99%, are solid. When the mantle becomes melt, it appears in magma form.When you wear concrete bodysuit, may be fight to break free from of it. You move your fingers and poke small holes. In the outer layer of the earth is some spots and cracks. These spot are created when the magma in the mantle pushes, And then volcano will form. When magma explodes it is called lava. Both of them, magma and lava, has the same composition to some extent and are melted rock.Plates are the big pieces of the crust separated with long the cracks like a giant drift.  Finally, when two plates hit into each other may one plate's edge slid under the other plate. Due to this collision subduction related volcanos build up. The plate in which slids  underneath the other plate suddenly forces a great pressure to the concrete bodysuit. Some part of them start to melt and generate magmas and cause severe strain. Two plates in the other section of the crust move away from each other, making a fissure in the crust. Fissure volcanoes permit magma to ooze up of the mantle along the fissure. Perhaps in future, two plates interchange their drift and push back  together to close the fissure. Volcanoes can shape exactly in the middle of the crustal plate. As the result of the magma melting a hole in the plate will create, oozing up magma, making hot-spot volcanoes. For example the Hawaiian Island is the result from hot-spot volcano structure.  Hawaii Island is not located along an edge of a crustal plate. On the contrary, it is near the center of the great Pacific crustal plate.  Hot-spot volcanoes explode often but like Hawaiian Island gradually pours out the lava.  Mantel start to melt in weak and thin parts of crust that strain is weak too. Consequently the explosion of such volcanoes is less powerful and rarely does happen with ash and rocks distribution. The magma arrives to the surface and ooze out, flowing like rivers of lava or like slow fiery spray of lava. The lava become cool soon after flowing,turning into volcanic rocks. Over millions of years Hawaiian Island is created exactly like this process. On contrary, subduction related volcanoes usually explode with great force.  Exploded drops of lava accompany with clastic sediments related to the explosion distribute in the air and go back around the volcano. A tremendous cloud of ash produce a great heat reactions by erupting. The thick clouds, such as clouds in the sky, prevent the sun to be seen and darken the sky in many kilometers around the volcano. The most important volcano mountain in Iran is Damavand whichWas active many years ago but has no activity now. This volcano erupted many volcanic rocks such as Basalt, Trachyt and some  pyroclastic materials such as pumice and lapilli.