The period of rotation of each galilean moon equal it period of revolution around jupiter

Yes, the number of days for a Galilean moon to rotate on its own axis equals to the number of days it revolves around Jupiter. For example moon Europa has 3.5 day revolution around Jupiter and it's rotation on its own axis also takes 3.5 days. This concept is basically due to the fact that each Galilean moon is being tide locked with Jupiter. 

Magma  is composed of molten rock and is  stored  in the earth's crust. lava is  magma  that reaches the surface of our planet through a volcano vent.