Dating of Rocks, Fossils, and Geologic Events

http://www.staff.zu.edu.eg/w.i.elwan/page.asp?id=53

 

Assignment: Activity 8.1, pg. 187, 8.2, pg. 189, 8.4, pg. 191.

Relative dating- Determining the age of something ________________ to the age of something else

• Law of Original Horizontality- most rocks were originally laid down ___________
• Law of Lateral Continuity- lava and _______________ rocks form a continuous bed
• Law of Superposition- younger rocks are located _________ older rocks
• Law of Inclusions- any rock fragment incorporated into another rock is ___________ than the rock it is found in
• Law of Cross-Cutting- ANY feature (like a magma dike or fault) that cuts into a preexisting rock is ___________ than the rock it disturbs .
• Law of Unconformities- gaps in the geologic record can be caused by ___________ or simply by a period of no deposition.
• Law of Fossil Succession- knowing the age of a fossil can indicate its relative age in relation to other layers containing index ____________. An index fossil lived for a brief period of time and was widespread.

Absolute Dating- Determining the ____________ age of something.

• Radiometric dating- finding the age of something by comparing the amount of radioactive isotopes to its stable _______ __________.
• Parent Isotope- the _________ radioactive isotope
• Daughter isotope- the stable ______ ___________ of decay
• Half-life- The time it takes for ____________ of the parent atoms in a sample to decay to its stable end product. Surprisingly, the rate is predictable and uninfluenced by heat, sample size or pressure.