Age dating of fossils
Trace fossils are just that: the traces of a creature left behind, usually in soft sediment like sand or mud.
For example, small animals bored branching tunnels in the mud of a lake bed in search of food; and dinosaurs hunted for meals along a river bank, leaving their footprints in the soft sand.
If this is not possible, certain analytical techniques are often used to determine the date of the rock layer.
One of the basic ways to determine the age of rock is through the use of radioactivity.
There is a difference between tracks and trails, too: tracks are generally the traces of distinct footprints, whereas trails may have been produced by an animal dragging its feet or some other appendage as it moved.
The record for fastest dinosaur, however, is presently held by a Jurassic carnivore that left a 16-foot (5-meter) gap between the right and left tracks in a Glen Rose, Texas, trackway.The calculated speed of this dinosaur was about 26.5 miles (42.8 kilometers) per hour, much faster than the speediest human.The age of fossils are determined by carbon dating and by radioactive calculations.If the mold is filled with sediment, it can often harden, forming a corresponding cast. These fish fossils are not actually bones, but rather imprints the fish made in the soil. Not all fossils are hardened bones and teeth, or molds and casts.There are also fossils that are merely evidence that creatures once crawled, walked, hopped, burrowed, or ran across the land.