the image shows core samples of rock strata taken from three different regions on earth. all the fossils…

Brief Explanation:

In undisturbed rock strata, the principle of superposition states that the lower layers are older and the upper - most layers are younger. In Region 1, the top - most layer with fossil F2 is the youngest. In Region 2, the top - most layer with fossil F4 is the youngest. In Region 3, the top - most layer with fossil F1 is the youngest. Comparing across regions, we focus on the top - most layers. Since no overturning took place, the youngest layer is the one at the top of any of the columns. Among the top - most layers, we can't further distinguish their relative ages based on the given information. For the oldest layer, in Region 1 it is the bottom layer with fossil F1, in Region 2 it is the bottom layer with fossil F3, and in Region 3 it is the bottom layer with fossil F3. Since we are looking for a single oldest layer among all, and considering the principle of superposition, the bottom - most layer in any of the columns is the oldest. Among the bottom - most layers, we assume they are all equally old in a general sense as no other age - comparison information is given for these bottom layers across regions. So the youngest layer is the top - most layer in any region (e.g., the layer with F2 in Region 1, F4 in Region 2, or F1 in Region 3) and the oldest layer is the bottom - most layer in any region (e.g., the layer with F1 in Region 1, F3 in Region 2, or F3 in Region 3).

Answer:

Youngest layer: Layer with F2 in Region 1 (or layer with F4 in Region 2, or layer with F1 in Region 3); Oldest layer: Layer with F1 in Region 1 (or layer with F3 in Region 2, or layer with F3 in Region 3)