The last layer to form was layer 12. According to the Law of Superposition, the bottom layers of sedimentary rock are the oldest, and each layer deposited on top is progressively younger.
Understanding the Law of Superposition
The Law of Superposition is a fundamental principle in geology. It states that in any undisturbed sequence of rock layers, the oldest layer is at the bottom, and the youngest layer is at the top. This is because new layers are deposited on top of older ones. Here's a brief overview:
- Layer 1: The oldest layer, deposited first.
- Subsequent Layers: Each layer deposited after layer 1 is younger than the one below it.
- Layer 12: The youngest layer, deposited last.
Layer Formation Explained
Sedimentary rocks are typically formed in horizontal layers. When sediment accumulates (e.g., sand, silt, mud), it does so on top of existing material. This process results in the formation of sequential layers, where each layer is a record of a specific period.
Practical Implications
Understanding layer formation is crucial for:
- Dating rocks: Geologists use the Law of Superposition to determine the relative ages of rocks.
- Interpreting geological history: The order of rock layers reveals the sequence of events that occurred over time.
- Finding fossils: Fossils are often found within specific layers, providing insights into past life.
