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.
If you are looking to see the Northern Lights, the time to visit is from September through March. Icelandic winters are not as cold as you might expect and the winter is in many ways a more interesting time to visit Iceland. There is a saying in Iceland, as in many other countries: âIf you donÂ´t like the weather, just wait 5 minutesâ.