Volcanic mountains can form away from plate boundaries. Magma rising in the mantle forms hot spots in the crust. As a plate moves over a hot spot, volcanic material erupts through the plate. Such eruptions form a chain of volcanic mountains. Sometimes magma rises toward the surface but does not break through the crust. It may push up under Earth's crust instead. This forms a dome-shaped mound. The melted rock then cools and hardens. This is how dome mountains are formed.