A subterranean magma chase
On August 16, 2014, a monitoring network detected an intense swarm of earthquakes beneath the Bárðarbunga volcano, which is buried under the vast Vatnajökull ice cap. This was the start of a remarkable geological event. Instead of rising vertically, a blade-like intrusion of magma, called a dyke, began to travel horizontally underground. For two weeks, scientists tracked this subterranean magma flow in near real-time. Networks of seismometers and GPS stations followed the magma's progress as it fractured rock, generating tens of thousands of earthquakes.
The dyke propagated over 45 kilometers to the northeast, extending from beneath the glacier to the Holuhraun lava field at a depth of 5 to 8 kilometers. The GPS data showed ground displacement of up to 14 centimeters, confirming the massive volume of magma being injected into the crust. This event provided a rare opportunity to observe the mechanics of a rifting episode—the process by which tectonic plates pull apart and create new crust. While the dyke was advancing, several small subglacial eruptions occurred along its path, creating depressions in the ice cap called cauldrons.