On the morning of his departure he put his planet in perfect order. He carefully cleaned out his active volcanoes. He also had one volcano that was extinct. So he cleaned out the extinct volcano, too. If they are well cleaned out, volcanoes burn slowly and steadily, without any eruptions.
Volcanic eruptions are like fires in a chimney.
On our earth we are obviously much too small to clean out our volcanoes. That is why they bring no end of trouble upon us. The little prince also pulled up, with a certain sense of dejection, the last little shoots of the baobabs. He believed that he would never want to return. But on this last morning all these familiar tasks seemed very precious to him.