Do you know the Geological Timeline?

Q: How are you coming along with the Geological Timeline?

A: Wellll..... So far I know:
              -Precambrian
              -Cambrian
              -Ordovician
And that's all I know.

What I plan on doing for memorizing the timeline is knowing a mnemonic device. "Please come over some day, maybe play poker. Two jacks cover two queens"
   -Precambrian  [Oldest]
   -Cambrian
   -Ordovician
   -Silurian
   -Devonian
   -Missippian
   -Pennsylvanian
   -Permian
   -Triassic
   -Jurassic
   -Cretocious
   -Tertiary
   -Quaternary   [Youngest]

Two days ago in class we made our own molds of fossils using sand, plaster and a shell. Today we get to dig out our shells.
Our mixtures included one with 25% plaster and 75% sand, another with 50% plaster and 50% sand and the third with 75% plaster and 25% sand. The easiest one to break the shell out of was the cup with 25% plaster and 75% sand but it was difficult to see the shell. The most difficult one to get the shell out of was the one with 75% plaster and 25% sand. The 50%/50% cup was the best sup even though it was difficult to get out [not as difficult as 75% plaster], it was clear the it was a shell.
Some strategies include putting the chuck of sand and plaster in a plastic bag and smashing it on the ground versus using scissors.