Fossils Flashcards
Where are fossils most commonly found?
In sedimentary rocks
When are sedimentary rocks found?
When clay and sand particles are carried from one place to another by water and wind
What are examples of sedimentary rocks?
Shale
Sandstone
Limestone
What are other places that fossils can be found?
Amber Tar pits Ice Volcanic lava Anaerobic swamps
What is amber?
Tree resin that has hardened
What is fossilisation?
The set of inorganic processes by which dead organisms or their parts are transformed into fossils
What are the ideal conditions for fossilisation to occur?
Organism should be covered immediately after death
Harder tissues are better suited to fossilisation
Underwater conditions assist in fossilisation as well
Why should the organism be buried right after death?
It creates anaerobic conditions
This prevents decay
Preserves the organism
Give examples of harder tissues which are often fossilised
Bone Shell Exoskeleton Hair Teeth Woody stems
Why is soft tissue rarely preserved?
It is easier to decay
When can soft tissues be preserved?
Insects in amber (even the hairs on the legs remained) In ice (skin and muscles remained intact)
What are the ten steps of fossilisation?
Death of organism
Rapidly covered by sediment
Soft tissues decay
Hard body parts are hardened or replaced by minerals
More sediment covers it
The sediment is cemented and compressed in layers
Sediment solidifies and forms sedimentary rocks
Fossils remain encased in rock for millions of years
They are pushed up due to the movement of the earth
They are exposed to the surface by the erosion of rock layers or human mining
They are then discovered and carefully removed by palaeontologists
What is petrification?
The process by which organic material, is replaced by minerals
Why is a river or ocean a good place for fossils to form?
Not as many aerobic bacteria (less O2), so less decay
Moving water covers the animal with sediment very quickly
How are fossils dug up?
Through a painstaking process
