Fossils in the Making

April 05, 2011

Photographer: Phil Lachman
Summary Author: Phil Lachman

The photo above, taken near Sydney, Australia, shows footprints in mud left behind by foraging dusky moorhens. Given the right conditions, these footprints may one day become fossils. When new layers of sediments, such as silt, mud or sand, are deposited over footprints, they may be preserved. If so, over millions of years and if sufficient sediment accumulates on top of them, the layer containing the footprints may be compressed and cemented to form rock. In this case, it is probably mudstone. The next stage in the life of the fossils would be uplift of the rock and then erosion. The overlying layers would slowly erode away until the footprints are revealed. Then a future geologist, if he or she knows where to look, might find them. In this way, fossil footprints of many creatures that lived before the arrival of Homo sapiens have been formed and later discovered. These include Australopithecus afarensis. Photo taken on March 23, 2011.

Photo details: Camera Maker: Canon; Camera Model: Canon EOS 50D; Focal Length: 95.0mm; Aperture: f/7.1; Exposure Time: 0.020 s (1/50); ISO equiv: 200; Exposure Bias: -0.33 EV; Metering Mode: Matrix; Exposure: aperture priority (semi-auto); White Balance: Auto; Flash Fired: No (enforced); Orientation: Rotate 90; Color Space: sRGB.