What causes earthquakes?

Volcanic eruptions causes earthquakes. Volcanic eruptions are caused when magma forces out of an opening in the Earth Crust and becomes lava on coming out of the opening of the Volcano. When magma forces out of the hole , then it causes a relative motion of the earth rptectonic plates or lithospheric plates. If this movement is caused in a vigorous manner , then it creates a tension force within the tectonic plates. After this tension force is released it leads to Eartquake.