Complex sentence: Tumisa, to the south of Lascar, was active between 2.5 and 0.4 million years ago, is composed of dacite and surrounded by pyroclastic flow deposits.
Split into simpler sentences: Tumisa, to the south of Lascar, was active between 2.5 and 0.4 million years ago. It is composed of dacite and surrounded by pyroclastic flow deposits.