La Reunion is a small island wedged between Madagascar and Mauritius. It is one of twenty-six regions of France and President Jacques Chirac is the head of state. The volcano is about 530,000 years old and has erupted an estimated 170 times since the mid 17th century.
The red hot lava cut roads in half, damaged homes and created huge clouds of steam as it flowed into the Indian Ocean.
It is the third eruption of the Piton de la Fournaise or 'Mountain of the Furnace' this year alone.
About 50 teenagers were taken to hospital from three schools in Saint Joseph with respiratory problems caused by the volcano's sulpher fumes.
Researchers on the island are concerned the recent activity may be creating more cracks lower down the volcano, which will allow the molten lava to spread further.