beak bird birds feather feathers frozen Heron herons ice leg legs Nyberg water winter adventure alpine alpinism alps altitude backpacking brave challenge climb climber climbing cold dangerous glacier glaciology global Graubünden hiking holiday ice-flow icy landscape man Morteratsch mountain mountaineer mountaineering mountains nature outdoor recreation risk silhouette snow sport sports summit swiss switzerland terrain tour tourism Trek Trekking warming against light bavaria deininger weiher germany lake sun sunrays sunshine animal animals North Pole polar pole sea seal sealife seals wild wildlife blue break broken crack danger fissure fracture norway slip slippery Expedition exploration extreme