Slideshow on what is a fossil and the six ways in which they can form

As scientists, we recognize that fossils are the preserved remains of animals or plants that are over 10,000 years old! There are two important types of fossils, body fossil and trace fossils. Body fossils are the remains  of animals or plants. Trace fossils are the reamains of an animal’s activity, like footprints or poop!

Sometimes, if an animal dies and gets buried quickly by dirt, sand, mud, or ash, it might turn into a fossil. As time passes, more and more sediment covers the remains of the animal. Uusually squishy parts rot away or are eaten by other critters, but hard things like bones and teeth often fossilize. 

There are six ways that a critter can turn into a fossil:

Bones and wood have pore spaces. Thos spaces can get filled in with minerals, forming a fossil that looks sort of like a bone-shaped rock!

Hard parts like bone, teeth, or shells slowly dissolve over time and get replaced by other minerals. 

Only a thin carbon film is left in the cirtter or leaf fossil. All other elements like oxygen, nitrogen, collagen, and hydrogen vanish. 

The really small crystals in the animal's hard parts turn into large crystals. the minerals of the fossil can change from heat and pressure without replacement. 

The original material disappears, leaving a space behind that can then get filled in to make a cast, just like dinosaur tracks or worm burrows. 

Critters can get preserved without change, like woolly mammoth hair or insects and leaves trapped in amber. 

Standards for What are fossils and how do they form?