New Zealand Quake's Strange Side Effect: What Are Earthquake Lights?

The magnitude-7.8 earthquake that rattled New Zealand early Monday morning local time (Sunday morning EST), killing at least two people and stranding many others in the region, also had a strange side effect: eerie blue and green flashes of light in the sky during the shaking. The strange light shows — which may appear as sizzling flames emanating from the ground, flashes of lightning, ghostly globes or blue and green shimmers — usually occur at rifts where huge chunks of Earth are pulling away from each other, according to a 2014 study published in the journal Seismological Research Letters. Also in 2014, researchers showed that shifting grains surrounding a fault may generate an electrical charge, though exactly why this happens is poorly understood.