The term 'LAVA SOURCE' can be broken down into two crossword solutions: ETNA (4 letters) and MAGMA (5 letters). Etna is an active stratovolcano located on the east coast of Sicily, Italy. It is one of the most active volcanoes in the world and is the highest volcano in Europe. MAGMA is molten rock that is found beneath the Earth's surface. It is formed when rocks melt due to extreme heat and pressure. When MAGMA reaches the Earth's surface, it is called lava. Therefore, both Etna and MAGMA are sources of lava.