Jack Dykinga / South rim of Moran Point at sunrise, with the Colorado River below, Grand Canyon National Park, Arizona, USA

Juan Carlos Munoz / Close up of foot of a hiker on the caldera rim of Los Gemelos, Santa Cruz Island, Galapagos, January 2009. Model released.

Fabio Liverani / Tree frog {Hyla sp} on rim of tropical fungus, Tambopata National Reserve, Amazonia, Peru

Jack Dykinga / Snow on Pinyon Pines (Pinus edulis) at sunrise, East Rim Drive, South Rim, Grand Canyon NP, Arizona, USA

Jack Dykinga / Ponderosa Pine (Pinus ponderosa) pine cone and needles in the snow, South Rim, Grand Canyon NP, Arizona, USA

Jack Dykinga / Sunset at Yaki Point on the South Rim with stratified rim rocks and minute storm clouds inside the canyon below, Grand Canyon National Park, Arizona, USA.

Pete Oxford / Sulphur fulmerole in crater of active volcano, Sierra Negra, Isabela Is, Galapagos

Yva Momatiuk & John Eastcott / Coyote (Canis latrans) looking for handouts from tourists, Mather Point parking lot on South Rim, Grand Canyon National Park, Arizona

Tim Fitzharris / South Rim of Grand Canyon with a dusting of snow seen from Yaki Point, Grand Canyon National Park, Arizona

Tui De Roy / Galapagos Giant Tortoise (Chelonoidis nigra) on caldera rim, Alcedo Volcano, Isabella Island, Galapagos Islands, Ecuador

Tui De Roy / Galapagos Giant Tortoise (Chelonoidis nigra) on caldera rim, Alcedo Volcano, Isabella Island, Galapagos Islands, Ecuador

Tui De Roy / Galapagos Giant Tortoise (Chelonoidis nigra) large male on caldera rim, Alcedo Volcano, Isabella Island, Galapagos Islands, Ecuador