Which dating method relies on the position of rock layers
It is estimated to require four hours of class time, including approximately one hour total of occasional instruction and explanation from the teacher and two hours of group (team) and individual activities by the students, plus one hour of discussion among students within the working groups.
Explore this link for additional information on the topics covered in this lesson: This activity will help students to have a better understanding of the basic principles used to determine the age of rocks and fossils. Objectives of this activity are: 1) To have students determine relative age of a geologically complex area.
~ One dating method is to compare objects found in similar layers of rock or soil.
~ Archaeologists may also compare an object with a similar fossil of artifact whose age is already known. Relative dating-comparing fossils related to how old other fossils are in the same sample of rock.
The teacher should tell the students that there are two basic principles used by geologists to determine the sequence of ages of rocks.
They are: Principle of superposition: Younger sedimentary rocks are deposited on top of older sedimentary rocks.
For relatively recent fossils, dating by carbon 14 is the most accurate method.
Some very straightforward principles are used to determine the age of fossils.
U-235 is the parent isotope of Pb-207, which is the daughter isotope.
Many rocks contain small amounts of unstable isotopes and the daughter isotopes into which they decay.
Where the amounts of parent and daughter isotopes can be accurately measured, the ratio can be used to determine how old the rock is, as shown in the following activities.
Part 2a Activity At any moment there is a small chance that each of the nuclei of U-235 will suddenly decay.For example, U-235 is an unstable isotope of uranium that has 92 protons and 143 neutrons in the nucl eus of each atom.