An intense earthquake swarm in Mt. Herðubreið in the NE Central Highlands shows no sign of slowing down. Nearly two hundred quakes have been detected just south of the volcano since the swarm began shortly after nine yesterday morning. At quarter to seven yesterday evening the Herðubreið swarm was joined by a 3.4 magnitude quake in the central caldera of the Bárðarbunga system. The Icelandic Meteorological Office located the epicenter of the 3.4 magnitude Bárðarbunga quake at a depth of only 800 m (o.5 mi) in the NE part of the caldera. A second 3.6 magnitude quake was detected in the same area on Monday morning. Geologists believe the seismic activity in Bárðarbunga is caused by the volcano refilling its magma chambers since the 2014-15 Holuhraun eruption, while it is not immediately clear what causes the Herðubreið activity. Mt. Herðubreið, like all mountains in Iceland, is an extinct volcano, formed in a single eruption 10-11.000 years ago, toward the end of the last Ice Age. It is