Video title: Fossils
250 million years ago, a three-toed dinosaur walked in the mud and left these footprints behind.
Footprints don't normally last this long, so what makes these so special?
They have lasted for millions of years because they became fossils.
Fossils
Fossils are the remains, or marks, left behind by ancient animals and plants.
As well as footprints, fossils can be impressions of an organism's shape, like this fossilised impression of a leaf.
They can be preserved whole organisms like this fossilised dragonfly, or the remains of animal bones, like this fossilised jawbone from a prehistoric mountain lion.
fossils
remains or marks of ancient organisms
Fossils can help us paint a picture of what extinct life forms looked like.
This is thought to be a fossil of the first bird.
It was called Archaeopteryx and lived on Earth 150 million years ago.
Archaeopteryx
This is an ammonite fossil.
ammonite
Ammonites are extinct molluscs that first existed in the seas 400 million years ago.
Fossils are rare, because they only form when the remains or marks of living things become trapped in a material and are buried.
This prevents them from being disturbed, eaten by predators, or broken down quickly by decomposers.
Over many years, the remains were covered in layers of sediment.
The weight of these layers transformed the sediment into sedimentary rock.
Very slowly, the plant or animal remains decayed and the space left behind was replaced by minerals from the rock.
The minerals hardened to form a fossil.
This process is called fossilisation.
fossilisation
remains replaced by minerals
minerals harden to form fossil
As for those footprints, soon after they were made they were baked hard by the Sun and then trapped within layers of sedimentary rock.
But over time this rock has been worn away, revealing the fossil treasures locked inside – footprints made by a three-toed dinosaur 250 million years ago.
Fossils are the remains or marks of ancient organisms.
Footprints don't normally last this long, so what makes these so special?
They have lasted for millions of years because they became fossils.
Fossils
Fossils are the remains, or marks, left behind by ancient animals and plants.
As well as footprints, fossils can be impressions of an organism's shape, like this fossilised impression of a leaf.
They can be preserved whole organisms like this fossilised dragonfly, or the remains of animal bones, like this fossilised jawbone from a prehistoric mountain lion.
fossils
remains or marks of ancient organisms
Fossils can help us paint a picture of what extinct life forms looked like.
This is thought to be a fossil of the first bird.
It was called Archaeopteryx and lived on Earth 150 million years ago.
Archaeopteryx
This is an ammonite fossil.
ammonite
Ammonites are extinct molluscs that first existed in the seas 400 million years ago.
Fossils are rare, because they only form when the remains or marks of living things become trapped in a material and are buried.
This prevents them from being disturbed, eaten by predators, or broken down quickly by decomposers.
Over many years, the remains were covered in layers of sediment.
The weight of these layers transformed the sediment into sedimentary rock.
Very slowly, the plant or animal remains decayed and the space left behind was replaced by minerals from the rock.
The minerals hardened to form a fossil.
This process is called fossilisation.
fossilisation
remains replaced by minerals
minerals harden to form fossil
As for those footprints, soon after they were made they were baked hard by the Sun and then trapped within layers of sedimentary rock.
But over time this rock has been worn away, revealing the fossil treasures locked inside – footprints made by a three-toed dinosaur 250 million years ago.
Fossils are the remains or marks of ancient organisms.
See the fossilised footprints of the first bird and discover how remains of organisms have been preserved for 150 million years.
Learning points
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