S wave -- a shadow zone appears when the velocity suddenly decreases 103-180 degrees from the epicenter. Describe the differences between P and S waves. P waves expand and contract, can move through liquid solid and gas. S wave moves up and down or side to side moves through only solids.
Optimal conditions to see the northern lights in Iceland is when skies are clear and dark (away from the city lights, in cold temperature and ideally from mid-September to mid-April.
NORTHERN LIGHTS in iceland. Crisp air in your lungs and unbridled beauty dancing overhead, the northern lights are truly a sight to behold. Experience an incredible natural phenomenon on a tour this winter in Iceland. ROOM TO BREATHE.