Ok, so today i made a new very simple model and i'd like just to discuss it with you all. Ive put a broken brick (x, y, z: 10, 2.5, 4 Splited up to 5, 2.5 and 5 (cm)) together in a marked with walls (20cm x 20cm x 5cm) area. The bricks were representing the earth's crust. Ive then brought a small can with Very hot water painted in red to represent the magma. Ive then splited it inside the area. The sample of hot water (magma) was a pretty big amout to fill up the whole area. As i was watching the progress of it i've noticed that the fault inside the 2 bricks was slightly filling up the water and the water splited apart the 2 bricks at a very small distance. What i belive is that the heat of the water forced the 2 bricks apart because of the pressure the hot water had. Sorry if this was a bad experiment but i'm not that old to know all this stuff! Also im sorry if my english are not readable, i'm Greek! I accept suggestions to make again the experiment better!