Name ______________________________
Fossils study sheet
Fossil- remains, imprints or traces of once living organisms. These can tell about an organism’s
environment, when and where it lived.
Fossils generally form when there is a quick burial – remains are kept away from scavengers.
AND there are usually hard parts in the fossils because soft parts decay easily.
Types of fossils –
1. perimineralized remains – minerals replace some of the original remains of an
organism.
2. trace fossils – an imprint, track, or burrow
3. cast – produced when sediments fill a cavity (mold) made when an object decayed.
4. Carbon film – a thin layer of carbon atoms and molecules.
5. Index fossils – fossils of species that existed for short periods and were widespread
6. Original remains – the actual organism is preserved as a fossil
Superposition – the principle that states that in a sequence of undisturbed rocks, the oldest
rocks are on the bottom.
Unconformities – gaps in the rock records made when erosion (or other factors) remove
existing rock layers.
Know the 3 types and what is different about each (angular unconformity, nonconformity, and
disconformity)- USE YOUR NOTES from class to study.
Be sure you can label rock layers by relative age and events (USE PACKET to study).
Half-life – the time it takes for half of an isotope’s atoms to decay.
Radioactive decay – the process when an isotope is changed or decays into other isotopes or
particles. In this process parent isotopes break down into daughter products.
Radiometric dating – the process that uses the properties of isotopes in rocks (or other objects)
to determine their ages.
Absolute age –the age in years of a rock or other object.
Know the process of mold/cast formation
1 A shell or organism gets buried in sediment.
2. The sediment hardens into rock.
3. Holes in the rock let water and air dissolve the shell, leaving behind a hollow place (cavity) in
the rock.
4. Other sediments fill the hollow place and harden into rock.
Know the principle of uniformitarianism – The present is the key to the past – In other words,
processes that are occurring today have always occurred at this speed and time.
Creation scientists do NOT agree with this principle – it leaves no room for God’s creation, or
for supernatural events. Also, there are evidences (recent canyon carving in a short time,
stone formation in a short time) –that show that this is definitely not always true.