A volcano in southwestern Iceland began erupting Monday with lava fountains reaching up to 330 feet and the glow visible miles away in the center of the capital, Reykjavik. The location of the fissure poses a risk to the nearby Svartsengi geothermal power plant and to the town of Grindavík, which was evacuated last month because of heightened seismic activity. “We are looking at a worst-case scenario,” said Thorvaldur Thordarson, a volcanologist in Iceland. “The eruption appears big, and only about two kilometers from major infrastructure.”