Authorities in the Democratic Republic of Congo have ordered as many as 1 million people to evacuate the city of Goma, as one of the world’s most dangerous volcanoes is threatening to erupt for a second time in a week. Lava from Saturday’s eruption left about 20,000 people homeless and killed at least 32 people. Powerful aftershocks and frequent tremors since then have rattled nerves and prompted fears over the fate of Goma, a densely populated city at the foot of the volcano.