Question

the diagram above shows a section of sedimentary rock that has gone through many changes over the years. the layers and the events that happened are numbered 1 - 10. which happened first? which rock layer or event is the oldest in the diagram above? 1 2 3 4 5

Explanation:

To determine the oldest rock layer or event, we use the principle of superposition (in undisturbed sedimentary layers, the oldest layers are at the bottom) and cross - cutting relationships (a feature that cuts through other layers is younger than the layers it cuts). Looking at the diagram, layer 10 is at the bottom among the sedimentary - like layers (considering the order of deposition and cross - cutting events). The cross - cutting events (like the faults or intrusions) are younger as they cut through existing layers. So layer 10 is the oldest as it is the lowest undisturbed - looking layer (before cross - cutting events), and in terms of the first - happening event related to layer formation, the layer at the bottom (layer 10) was deposited first.

Answer:

10 (the rock layer or event numbered 10 is the oldest and happened first)