Fossils Flashcards
What is a fossil?
Preserved evidence (remains or traces) of ancient life
Body fossils
Body parts such as bonest, teeth, and skin
Trace fossils
Evidence of their day-to-day activities such as footprints, trails, or burrows
The only way an organism can become a fossil
If it’s protected from decomposition, scavenging, weathering, erosion, or any other process that may destroy the remains
How are fossils made?
- Over time, high spots wear down and low spots fill up (weathering breaks down rocks, and erosion transports sediment downhill)
- The sediments are slowly buried and turn to rock
- If we are lucky, sediments will also bury organisms and protect them from destruction
- The more rapidly an organism is buried, the more likely it is to fossilize
- Once an organism is buried, chemical changes may take place and turn it into a fossil
9 ways to fossilize anything
- Freezing
- Mummification / Desiccation (Jerkify)
- Encasement (Cover them in something sticky)
- Replacement
- Permineralization (Fill the void)
- Petrification (Petrify it)
- Recrystallization
- Carbonization (Leave a film)
- Molds and Casts
1,2, and 3 make for the best fossils
Encasement
- In amber (think of the spider about to eat a wasp example)
- In tar (Soft tissues break down, but the bones get “pickled. The original hard parts are still there, but turn black and smell like tar)
Altered remains
When remains become fossilized due to chemical reactions that change their composition
Altered remains usually turn into stone
Replacement
Original bone or shell material is dissolved and another mineral immediately take its place
Permineralization
Water flows through pores and deposits minerals
- Common in bones
Petrification
Permineralization + replacement
- Common in wood
Recrystallization
Change in the crystal structure or the size of crystals (they get bigger)
Carbonization
Bury it and squeeze all the water and other volatiles out until there is only a film of carbon left on the rock
