Simplify the following text for a Grade 8 native English-speaking person.
Original: In 1971 , lava buried the Etna Observatory ( built in the late 19th century ) , destroyed the first generation of the Etna cable-car , and seriously threatened several small villages on Etna 's east flank .
Simplified: In 1971 , it buried the Etna Observatory ( built in the late 19th century ) under lava .