Complex sentence: The territory was formed by mostly basaltic magma (within the last 100,000 years) derived from fissural eruptions around the area of Pico da Bagacina, that produced fluid lava that flowed to the coast of the island.
Split into simpler sentences: The territory was formed by mostly basaltic magma within the last 100,000 years. Fissural eruptions around the area of Pico da Bagacina produced fluid lava that flowed to the coast of the island.