Question

a river has cut a channel deep into the earth and exposed several layers of undisturbed sedimentary rock as shown in the cross section. cross section of channel which layer is the youngest?

Explanation:

Step1: Recall the law of superposition

In undisturbed sedimentary rock layers, the younger layers are on top of older layers.

Step2: Analyze the given cross - section

Looking at the cross - section of the channel, layer 1 is at the top of the sequence of layers (layers 1, 2, 3, 4). According to the law of superposition, since the layers are undisturbed, the layer at the top is the youngest. So layer 1 is the youngest.

Answer:

Layer 1