Which describes the difference between the law of inclusion and the law of crosscutting in relative dating of rocks and • Intruding objects are younger in the law of inclusion and fossils
Intruding objects are older in the law of inclusion.
• Bottom layers of rock are older only in the law of crosscutting.
• Bottom layers of rock are younger only in the law of crosscutting.
The law of inclusion and the law of cross-cutting are both principles used in relative dating of rocks and geological features, but they describe different situations and phenomena. Here's a succinct differentiation:
- **Law of Inclusion:** If rock or fragments of rock (inclusions) are found within a layer, these inclusions must be older than the layer that contains them. For instance, if you find pebbles or boulders within a sedimentary rock layer, the pebbles or boulders must have existed before the sediment that surrounds them hardened. This principle is also applicable when considering fossil content; if fossils are included within a rock layer, they predate the formation of the rock layer.
- **Law of Cross-Cutting:** This law states that any geological feature (such as a fault or an intrusion) that cuts across or disrupts another feature must be younger than the feature it disrupts. For example, if an igneous dyke cuts through a sequence of sedimentary rocks, the dyke is younger than the rocks it cuts across.
Regarding the bullet points provided:
- "Intruding objects are younger in the law of inclusion" is incorrect; the law of inclusion does not specifically deal with intruding objects in this sense. Instead, it refers to pieces of rock or material that are included within a rock layer. The correct principle associated with intruding objects is the law of cross-cutting, which states that intruding objects (like magma or a fault) are younger than the rock layers they cut through.
- The statements about the bottom layers of rock being older or younger only in the law of cross-cutting are misinterpretations. The principle that generally describes the relative age of bottom layers is the law of superposition, which states that in an undisturbed sequence of sedimentary rocks, the oldest layers are at the bottom and the youngest are at the top. This is not specific to the law of cross-cutting.
In summary, the law of inclusion concerns materials contained within a rock layer, indicating that the inclusions are older than the host rock, while the law of cross-cutting relates to features that cut across existing structures, indicating that these cross-cutting features are younger than what they disrupt. Neither principle indicates that bottom layers are exclusively older or younger – that concept is rooted in the law of superposition.