In the Gulf of Carpentaria in northern Australia, an extraordinary phenomenon called the morning glory cloud occurs between September and November. The cloud forms as a wave-shaped formation up to 3.2 km high and 600-1000 km wide, moving at 40 km/h from east to west. Scientists believe it is caused by a clash of warm, moist air from the sea sliding over cooler air layers in the early morning. While similar air mass clashes occur elsewhere, including the Catalan coast of Spain, the morning glory cloud formation is unique to Australia. Hang gliders and paragliders have surfed the cloud waves since 1989, though it can be dangerous due to strong turbulence.