Postcards From Eden
Postcard 5
Edition of 40
Photographic montage
5" x 7"
Original image - Lake Clifton Yalgorup National Park
Western Australia

Rock-like structures known as thrombolites can be seen on the edge of Lake Clifton. Like the famous stromatolites of Hamelin Pool, in Shark Bay, the thrombolites are built by micro-organisms too small for the human eye to see. Within the structures of Lake Clifton, are living communities of diverse inhabitants with population densities of 3000 per square metre! The thrombolite-building micro-organisms of Lake Clifton resemble the earliest forms of life on Earth. The discovery of modern examples helped scientists to understand the significance of micro-organisms in the environment and unravel the long history of life on Earth. These organisms were the only known form of life on Earth from 3500 million to 650 million years ago. The thrombolites and stromatolites they constructed dominated the clear, shallow seas of this period and formed extensive reef tracts rivalling those of modern coral reefs. Similar organisms, for instance, helped to form the rich iron-ore deposits of the Hamersley Range, in the Pilbara's Karijini National Park, some 2000 million years ago. At this time oxygen made up only one per cent of the atmosphere. When there was no more iron to precipitate, the free oxygen leaked into the atmosphere until it formed 21 per cent of atmospheric gases.