Question

the diagram shows different layers of sedimentary rock. each layer is labeled with a letter.
which statement correctly describes the relative ages of the rock layers shown in the diagram?
○ the left part of layer b is younger than the right part.
○ layer r is older than layer m.
○ the left part of layer f is the same age as layer m.
○ layer i is older than layer b.

Explanation:

According to the principle of superposition, in undisturbed sedimentary rock layers, the lower layers are older. Also, when a fault or intrusion occurs, it affects the existing layers. For example, if there is a fault cutting through layers, the parts of the layers on either side of the fault were originally continuous.

• For the option "Layer I is older than Layer B": According to the principle of superposition (in normal sedimentary deposition, lower layers are older), if Layer B is below Layer I, this statement is wrong.
• For the option "The left part of Layer F is the same age as Layer M": If there was a continuous layer that was later disrupted (e.g., by a fault or erosion - deposition event), the originally continuous layer (Layer F) would have parts (left part) that are the same age as another layer (if there was no new sediment input for Layer M during the disruption time, this could be wrong. But if it was a continuous layer before disruption, this is correct.
• For the option "Layer R is older than Layer M": If there is an intrusion (assuming R is an intrusion), intrusions are younger than the layers they intrude into. If M is below R (assuming normal geological context), this is wrong.
• For the option "The left part of Layer B is younger than the right part": If there was a deposition event where the right part was deposited first (lower in a vertical sense in original deposition) and then the left part (higher in original deposition, but due to tectonic activity like tilting, but in original deposition lower = older), this is wrong.

Assuming the diagram shows that Layer F was a continuous layer (before some geological event like faulting) and Layer M is part of the same original continuous layer as the left part of Layer F (before disruption), the statement "The left part of Layer F is the same age as Layer M" is correct.

Answer:

The left part of Layer F is the same age as Layer M.