All About Fossils
As a youngster I remember the excitement and intrigue at turning over rocks on the beach to reveal fossils. I found it a fun way to learn about about fossils.
Fossils are the remains of prehistoric life. They can also be other forms of evidence that such life existed. In order to become fossilised three basic conditions must be satisfied. Firstly, an animal or a plant would normally have to have hard parts such as shell or wood or bone. Secondly, this must then be buried quickly to prevent decay and thirdly, this must remain undisturbed throughout the whole process of fossilisation.
Some remains are preserved through a different process and in these rare cases, the animals have been preserved through freezing. An example of this are the discoveries of Mammoths as seen in Alaska and Siberia. These examples have been refrigerated in the freezing ground for the past 25,000 years.
A further example of animals being preserved comes from semi-arid regions. In South America, mummified Ground Sloths have been found in caves, preserved by the unusual mixed conditions of cold, dryness and chemical action.
Fossils - Life from the Past
It is rare to find fossils that are complete. For example, we might find an animal where only the skull or a few bones remain. Or we might find a fossil of a leaf. So how is it that we can then translate this partial fossil remain into an image of what the whole animal or tree might have looked like.
Geologists do this by understanding what animals and plants are like today. They use their knowledge of today's animal and plant life to interpret the remains. An example might be Ammonites, these have been extinct for some 70 million years, however there shells are similar to living Pearly Nautilus. The geologist assumes that the soft parts were also similar and reconstruct them to match.
Types of Fossils
So what types are fossils are there?
There are many types fossils and they are not always remains of bones or shells.
Below are a few of the most common types of fossils.
Mold Fossils are hollow impressions left in rocks.
Cast Fossils are mineral deposit filled molds that leave a copy of the creature or plant behind.
Imprint Fossils are from things such as footprints of creatures or even drag marks.
Whole Fossils happen when plants or animals are encased in ice or sap - an example of this would be an insect trapped in amber.
The most common form of fossils are the remains of shells or bones that have been transformed into stone. These can often show most if not all of the original detail of the shell or bone in minute detail. This is due to all the pores and tiny spaces in their structure being filled with minerals compounds like calcite which is calcium carbonate, which is dissolved in water. As the water passed through the shell or bone minerals were deposited in the spaces within the shell or bone structure.
Types of Fossil
How Fossils are Formed - A great explanation of fossils for kids - from YouTube
A fun activity for kids to make their own fossils.
You can create your own "fossils" by following the instructions below. You can use anything small to form the fossil imprint. Examples might be leaves or shells.
You will need the items below:
Modelling clay. Waxed paper. Plaster of Paris. Some vegetable oil. A container in which to mix the plaster of Paris.
For each item that you would need to fossilise you should do the following:
Step 1. place a ball of clay on a piece of waxed paper and flatten it into a thick circle.
Step 2. make an impression in the clay. You do this by gently pressing in the object and then carefully remove it.
Step 3. apply a little vegetable oil to the surface of the impression you have made (this makes it non-stick).
Step 4. Follow the directions on the Plaster of Paris package so that it has the right consistency, then spoon the plaster of Paris into the impressions.
Step 5. Leave the plaster to dry, which usually takes around 45 to 60 minutes, then peel away the clay. Your fossil will be revealed.
Types of Rocks
These rock types are those were fossils are most commonly found
Sedimentary Rocks the majority of fossils are found in sedimentary rocks. As the name suggests, these rocks are formed of sediments from clay, sand or mud.
Limestone fossil finds are also seen in this type of rock. Made mainly from calcium carbonate, limestone is common in warm shallow seas.
Shale another type of rock that preserves fossils. Made up of fine grains from clays and silt.
People collect fossils for all sorts of reasons. For fun or for the excitement of that rare find. Sometimes it is just for the fact that it gets you outside and in the company of other like minded people.
So where should you look for fossils? The simple answer is to look in sedimentary rocks. Rocks that have been freshly exposed are the best source. Along the beach, river bank and headland can be good sources. A word of warning though - always get permission from the land-owner and always watch out for loose rocks. Remember - safety first!
Take time to survey the area, looking for those rock surfaces have weathered, possibly exposing fossils. You should turn over rock fragments looking on both sides.
In the event that you discover bones such as vertebrae, you should leave the find intact and seek professional help. You wouldn't want to ruin what might be a significant and important find.
Fossil Hunting - From Discovery Channel - A youtube video
The Great Fossil Hunters
It was during the 1800's that scientists learned a great deal about the study of rocks (geology), and about the history of life (palaeontology).
The first important fossil finds were made by William Buckland, a professor of Geology at Oxford University, England in the 1820's. He named these finds "Megalosaurus" which means giant lizard.
In 1825, Mary Ann Mantell found a large fossil tooth - this was later found to be from an Iguanodon.
It was from early fossil hunters such as these that a whole new world of dinosaurs first emerged.
Modern Day Fossil Hunting
Tools for Fossil Hunting
- A geologist's hammer
- A shoulder bag
- A small cold chisel
- A first aid kit
- A map
- Your own food and water
- Something to wrap your finds in - newspaper can be good.
Storing and Displaying Fossils
Fossils can be stored in cardboard trays. Labels can be written up and placed beneath the fossil. Alternatively, a bank of shallow drawers can be used. Another alternative is to use plastic or glass jewelry cases.
You should first clean your fossils by brushing away the dirt - an artists brush would do the job nicely. You should also wash away any salt from the sea - soak then in cold water for a few minutes and then let them dry in the air.