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.
Once in a while the northern lights will take Reykjavik reykjavÃ­k by surprise and they are so strong that the city lightsâdon t, matter but most of the, timeâit s best to get away from all the street lights and car. brightshis of course means that the Auroras are often happening, even if they arenât visible to us down on the ground. In the northern hemisphere, the lights are best seen from Iceland, Greenland, northern Norway, Siberia, the Canadian territories and Alaska.