Residents of a fishing town in southwestern Iceland left their homes Saturday after increasing concern about a potential volcanic eruption caused civil defense authorities to declare a state of emergency in the region. Police decided to evacuate Grindavik after recent seismic activity in the area moved south toward the town and monitoring indicated that a corridor of magma, or semi-molten rock, now extends under the community, Iceland’s Meteorological Office said. The town of 3,400 is on the Reykjanes Peninsula, about 50 kilometers (31 miles) southwest of the capital, Reykjavik. “At this stage, it is not possible to determine exactly whether and where magma might reach the surface,” the Meteorological Office said. Authorities also raised their aviation alert to orange, indicating an increased risk of a volcanic eruption. Volcanic eruptions pose a serious hazard to aviation because they can spew highly abrasive ash high into the atmosphere, where it can cause …