A mold is formed when a deceased animal is buried by sediment from the Earth. As the animal starts to decay, a chamber remains in the shape of the animal. A fossil cast is made when minerals are deposited in the mold.Know More
There are two types of molds created by a fossil: external and internal. The external mold is made when the organic materials on the creature decay, leaving behind an imprint of the external shape and characteristics of the animal. And internal mold is created when a hollow organism fills with sediment and minerals after it dies. As the shell decays, an imprint of the organism is left in the minerals that creates the fossil.
Though casts can be made through natural processes, many of them are made though artificial means. Students and researchers create a mixture using clay and plaster of paris to cover the fossil. The concoction is allowed to dry before being removed. This creates an exact replica of the fossil that is more durable than the original, allowing for it to be handled and studied without compromising the original artifact. These synthetic casts can be made using both external and internal molds of the fossil.Learn more about Biology
Index fossils are fossils that are found often in many different areas of the world. These types of fossils help to date other fossils that have been found in the same sedimentary layer of the Earth.Full Answer >
The fossil record is incomplete because it takes an extremely specific set of circumstances for a dead plant or animal to become a fossil. The vast majority of living things simply die and decompose without leaving a permanent record of their existence.Full Answer >
Sedimentary rocks are formed from sediment that is accumulated and compacted over time, while metamorphic rocks are the result of heat and pressure deep within the Earth's surface. Igneous rocks are created when magma reaches the surface and then cools and hardens.Full Answer >
Ammonite fossils are the remains of prehistoric sea creatures that are spiralled in shape and resemble a ram's horn. According to Cochise College, ammonites first appeared approximately 450 million years ago and became extinct at the end of the Cretaceous period about 65 million years ago.Full Answer >