Iceland’s Reykjanes peninsula saw its second volcanic eruption in less than a month on Thursday, when seismic activity sent fountains of lava streaming into the air and molten rivers spewing across the plains. The lava flow jumped a road near the popular geothermal spa the Blue Lagoon, closing the luxury resort for the second time this year, and damaged a hot water supply pipeline, cutting off access to more than 20,000 people. As a result, authorities issued an emergency alert and conservation warnings to residents, although the eruption did not interrupt flights from Iceland’s international airport some 12 miles away nor immediately threaten any townspeople. The fissure opened 2.5 miles away from the small fishing village of Grindavik, which was evacuated after an earlier, closer eruption on Jan. 14. Iceland, known to be a hotbed of volcanic activity, is historically prone to eruptions every 5 years. Thursday’s event was the third eruption since December.