Fossils Flashcards
what is the definition of fossil?
any preserved remains of a once living organism
why are fossils important to scientist ?
allows them to build a sequence of evolution of particular organsims
what is a petrified fossil
the turning of something into stone
how is a petrified fossil formed?
water full of minerals seeps into the layers of sediment to reach the dead organism when the water evaporates the minerals harden called perminralisation
how is a mold fossil formed?
when the hard parts of an organism are buried in sediment and then they dissolve leaving a hollow area
how is a cast fossil made?
water with dissolved minerals and sediment fills the molds it then evaporates only leaving the minerals
how are carbon films made?
when an organism dies eventually there will only be carbon left this shows the organisms delicate parts
what is a trace fossil ?
shows the activity of an organism eg footprint set in sediment
what is a preserved remain?
an organism that gets preserved in or close to there original state
what is a preserved remain in amber?
an organism gets trapped in sticky tree resin it then gets covered more
what are preserved remains in tar?
organsims get trapped in a tar pit dies and then the tar soaks into the bones resulting in bones to stop decaying
what are preserved remains in ice?
organism dies in a very cold region its body gets frozen in ice which preserves the organism
what is vital to the formation fossils ?
-organism becomes fossilised when buried
-buried rapidly or in wrong conditions decomposition occurs
-wet and acidic soil dissolves bone
-no oxygen
how are fossils discovered?
- erosion = earth movement and excavation
what is the process of a fossils discovered?
-excavation sites
-sections are marked out
-small handed tools used to remove soil
-soil is sieved
-photographed at each stage
-each item is labelled and catalouged
-fossils clean
what is fossil dating and what are the two types?
determines the age of the fossils
absolute dating = actual age of specimen in years
relative dating = tell us wether a sample is older or younger then another
what are the two types of absolute dating ?
potassium-argon
radiocarbon
what is potassium-argon dating based on ?
the decay of radioactive potassium-40 into calcium-40 and argon-40
what is the age range that potassium-argon dating can be used on?
rocks aged older then 100,000-200,000 year old
what are the limitations to potassium-argon dating?
-it has to be older than 100,000 years old
-not all rocks have potassium in them
what is radiocarbon dating based on ?
carbon-14 decaying into nitrogen
what is the age range that radiocarbon dating can be used on?
60,000 year
what is the limitations to radiocarbon dating ?
can only be used after 60,000 years
give an overview of carbon-14 and how it used
-animals eat carbon 14 when they die the decay of carbon 14 remains consistant
- this is then compared to the carbon 12 to determine the age
what is dendrochronology ?
tree ring dating which can help verify radiocarbon dating
what is the age range that dendrochronology can be used on?
up to 9,000 years old
what is relative dating using ?
-the stratigraphy
-the principle of superposition
-correlation of rock strata
-fluoride dating
what is fluoride dating ?
based on the number of fluoride ions that are replacing the other ions in the bones.
what is potassium -40 half life
1.25 billion years
what is carbon -14 half life?
5730 years
