Well, the cause of a volcanic eruption is when the lower crust melts. This leads to the formation of magma. The volcano is an opening through which the magma is discharged. The rock inside the earth melts. This magma is diffused upwards through the volcano. If magma reaches the top of the volcano, it behaviour depends on viscosity. So what happens before a volcanic eruption is that the lower crust melts, causing the formation of magma, which is released through the volcano. Hope i helped.
In the given above, we have two densities which are 0.89 g/mL and 0.72 g/mL. We are also given that the liquids are immiscible. After the settlement of the liquids, they will form two layers.
The heavier substance, the one which has a higher density will be at the bottom and the lighter substance, the one which has a lower density will be at the top layer.
