| A | B |
|---|
| fossils | grouped based on how they were formed |
| mold fossil | forms when sediements bury an organism and the sediments are compacted into rock; the organism decays leaving a cavity in the shape of an organism ( the pan) |
| cast fossil | forms when a mold is filled with sand or mud or other sediment that then hardens intot eh shape of the organism ( the cake shaped like the pan) |
| petrified fossile (permineralized fossile) | forms when mineral dissoved in a solution soak into the buried remains of an organism, replace the remains and end up creating a "rock replcia" a mineral copy of an organism |
| original remails/ perserved fossil | forms when parts of the entrie organism is prevented from decaying by being trapped in rock, ice, tar, or amber |
| carbonized fossil (carbon film) | forms when an organism is pressed between layers of sediment that eventually hardens to rock. The pressure of rock compaction squeezes away almost all of the decaying organism leaving only the carbon imprinted in the rock. (most frequently leaves, steams, flowers, fish, and other marine organisms) |
| trace fossils | forms when sediemnt (r ash or extrusive igneous rock) hardens to stone where a footprint, trail, or burrow of an organism was left behind; indicates activity of organism |
| relative age | older than/younger than, not a measurement |
| law of superposition | sedimentary layering results in older rocks being found underneath younger rocks |
| principle of cross cutting relationships | an intrusion is younger than rock through which it cuts |
| absolute age | earth is calculated to be 4.6 billion years old |
| elements | decay or turn into a new element |
| radioactive decay | occurs at a constant rate, by measuring the amount of radioactive element and amound of daughter element in an igneous rock the age can be calculated can not be done with sediementary rock |
