Examine the diagram below, which is a diagrammatic sketch of ...

[big1devin]

Examine the diagram below, which is a diagrammatic sketch of geologic features exposed in cross section in a deep river canyon.
 
  Write a paragraph that summarizes the geologic history at this locality, using the letter labels to describe the different rock units. Your history should be chronological, starting with the first event and ending with the most recent. Identify unconformities where they exist.
  What will be an ideal response?

Question 2

In order to apply the isotope-dating method, what must be known or measured, and what conditions must be met?
 
  What will be an ideal response?

[ecox1012]

Answer to Question 1

Please note error in drawingM in the magenta igneous intrusion (T), which should have a line pointing toward the xenolith.
Formation of parent rock for M
Metamorphism to form M
Intrusion of T
Faulting of T by fault F1
Deposition of Y, H, D
Intrusion of Z
Tilting/folding of M, T, F1, Y, H, D, Z
Erosion to form a flat surface
Deposition of P, G, A
Faulting by fault F2
Tilting of all rocks that formed to this point
Erosion to form a flat surface
Deposition of S
Erosion along river through S and A
Deposition of B in river channel

Answer to Question 2

The half-life or decay rate must be known. There must be no daughter isotope present when the rock forms or we must be able to determine how much daughter was present. No parent isotope can be lost or gained from the rock since it formed. No daughter isotope can be lost or gained from the rock since it formed and radioactive decay begins. Accurate measurements of the abundances of parent and daughter isotopes, and the half-life value of decay. As instrumentation improves, the ability to detect and measure parent and daughter isotopes improves as well as improved precision. As precision increases, accuracy will too.