Igneous rocks, such as those formed when volcanoes erupt, often contain some radioactive elements.
(those; formed; ) (volcanoes; erupt; ) (Igneous rocks, such as those; contain; some radioactive elements; T:when volcanoes erupt; T:often)
those volcanoes Igneous rocks, such as those
formed erupt contain
some radioactive elements T:when volcanoes erupt T:often