What fossils are
Fossils are the evidence of life on earth many millions of years ago. They are always found in sedimentary rocks, which formed mainly in lakes, seas and swamps. Fossils are the remains of plants and animals, and in soem cases almost the entire bodies of animals have been preserved.
Some fossils are petrified or turned to stone, some are carbonised or turned to carbon, and other are moulds or casts. Animal tracks and the marks made by waves and winds have been fossilised in certain kinds of rock strata and formations.
The rocks containing fossils were once buried deep under other layers of sedimentary rock, but from time to time the earth’s surface moves, such as when mountain ranges are formed, and the old rocks become exposed. Erosion wears away the rocks and we can see the fossils.
How fossils are formed
Usually, when an animal dies in the open, wind and rain will soon crumble even the hardest bones. But if the dead creature is quickly covered over by sediment, it is protected from decay. When there are many fossils of sea creatures in rocks, it is usually because the sea bottom was covered in a thick, soft ooze. Dead creatures sank to the bottom and later became sedimentary rock.
The early creatures of the Pre-Cambrian period were probably soft-bodied and so their remains were not so easily preserved. When creatures developed shells, bones and teeth, their remains could become fossilised much more easily.
Because animal bodies usually decay after death, few have survived in their original state. However, some woolly mammoths have been discovered in the frozen soil of Alaska and Siberia. Here, the climate has been arctic for many centuries and the mammoths were preserved by the cold just as they died. In fact, even though the bodies were 30,000 years old when they were discovered, the meat was still fresh.
Fossils become petrified, that is, turned into stone when the dead creature is buried and the soft parts to decay. Water containing a mineral such as silica seeps into the spaces left by the decayed parts, like was filling a mould. Over many years the silica completely fills the spaces and eventually process takes place with the trees and plants. One famous example is the petrified forest in Arizona.
Looking for fossils
If you want to look for fossils, first find a place where sedimentary rocks are exposedm sucn as a canyon, a sea cliff or a quarry. A good way to start is to pick up and carefully examine small pieces of rock that have fallen down. If the fossil is in a big piece of rock you can chio the whole piece away wuth a chisel or a geologist’s hammer, but the rock around the fossil itself must be removed very carefully with a smaller tool like an awl, for fossils are very fragile.
Fossils are the evidence of life on earth many millions of years ago. They are always found in sedimentary rocks, which formed mainly in lakes, seas and swamps. Fossils are the remains of plants and animals, and in soem cases almost the entire bodies of animals have been preserved.
Some fossils are petrified or turned to stone, some are carbonised or turned to carbon, and other are moulds or casts. Animal tracks and the marks made by waves and winds have been fossilised in certain kinds of rock strata and formations.
The rocks containing fossils were once buried deep under other layers of sedimentary rock, but from time to time the earth’s surface moves, such as when mountain ranges are formed, and the old rocks become exposed. Erosion wears away the rocks and we can see the fossils.
How fossils are formed
Usually, when an animal dies in the open, wind and rain will soon crumble even the hardest bones. But if the dead creature is quickly covered over by sediment, it is protected from decay. When there are many fossils of sea creatures in rocks, it is usually because the sea bottom was covered in a thick, soft ooze. Dead creatures sank to the bottom and later became sedimentary rock.
The early creatures of the Pre-Cambrian period were probably soft-bodied and so their remains were not so easily preserved. When creatures developed shells, bones and teeth, their remains could become fossilised much more easily.
Because animal bodies usually decay after death, few have survived in their original state. However, some woolly mammoths have been discovered in the frozen soil of Alaska and Siberia. Here, the climate has been arctic for many centuries and the mammoths were preserved by the cold just as they died. In fact, even though the bodies were 30,000 years old when they were discovered, the meat was still fresh.
Fossils become petrified, that is, turned into stone when the dead creature is buried and the soft parts to decay. Water containing a mineral such as silica seeps into the spaces left by the decayed parts, like was filling a mould. Over many years the silica completely fills the spaces and eventually process takes place with the trees and plants. One famous example is the petrified forest in Arizona.
Looking for fossils
If you want to look for fossils, first find a place where sedimentary rocks are exposedm sucn as a canyon, a sea cliff or a quarry. A good way to start is to pick up and carefully examine small pieces of rock that have fallen down. If the fossil is in a big piece of rock you can chio the whole piece away wuth a chisel or a geologist’s hammer, but the rock around the fossil itself must be removed very carefully with a smaller tool like an awl, for fossils are very fragile.
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