Lava lakes are large volumes of molten lava, usually basaltic, contained in a volcanic vent, crater, or broad depression. The term is used to describe both lava lakes that are wholly or partly molten and those that are solidified. Persistent lava lakes are a rare phenomenon. Only a few volcanoes have hosted persistent or near-persistent lava lakes during recent decades. A certain number of occurrences of temporary lava lakes (sometimes called lava ponds or lava pools, depending on their size and nature) have also been observed. (wiki)