click below
click below
Normal Size Small Size show me how
Rel and Abs Dating
Question | Answer |
---|---|
Relative Dating | Places events in sequence without assigning any numerical ages. |
Law of Horizontality | States that all rock layers are initially laid down horizontally. If one or more layers are not horizontal this indicates some sort of tectonic action such as uplifting. |
Principle of Superposition | States that in a sequence of undisturbed sedimentary rocks, the oldest rock will be at the bottom of the sequence and the youngest will be at the top. |
Principle of Cross Cutting | States that an igneous rock is younger than the rocks it has intruded (cut across). |
Principle of Included Fragments | States that pieces of one rock in another rock must be older than the rock in which they are found. |
Unconformity | A place in the rock record where the layers of rock are missing. Unconformities are gaps in geologic time. |
Absolute Dating | Time places a numerical age on an event. This is difficult and expensive to obtain. |
Radioactive Decay (Carbon14 dating) | Used to determine the absolute age of rocks. |
Half life | The time required for half a given sample of a radioactive isotope (atom that has a different number of neutrons than the standard for that element) to decay. |
Carbon 14 | Is a method of dating that is only used on objects that were once living. |