They are called Morning Glory clouds and, says NASA. Nobody is quite sure what causes them.
This shot was taken by photographer Mick Petroff from a plane near the Gulf of Carpentaria and posted online by NASA.
A Morning Glory cloud can roll for 1000 kilometres at altitudes up to two kilometres high. These, over Burketown in Queensland happen every spring, says NASA.
"Long, horizontal, circulating tubes of air might form when flowing, moist, cooling air encounters an inversion layer, an atmospheric layer where air temperature atypically increases with height," says NASA on its website.
"These tubes and surrounding air could cause dangerous turbulence for airplanes when clear. Morning Glory clouds can reportedly achieve an airspeed of 60 kilometers per hour over a surface with little discernible wind.
