Question

The Principle of Inclusions states that

1. an inclusion is always the same age as the rock matrix in which it is contained
2. an inclusion is always older than the rock matrix that encloses it
3. the largest inclusions in a rock are always the youngest
4. the smaller the inclusion the more recently it was incorporated into the rock
5. an inclusion must be younger than the rock matrix that surrounds it

Answer 1

The Principle of inclusion indicates that an inclusion is older than the surrounding rock matrix. It helps to establish the sequence of geological events by determining that the inclusion predates the formation of the enclosing rock.

Step-by-step explanation:

The Principle of inclusion states that an inclusion is always older than the rock matrix that encloses it. This is a foundational concept in the field of geology, specifically in the context of relative dating. When examining the relationship between a rock matrix and the inclusions within it, we can deduce that the inclusions had to exist first before they could be enclosed by the rock that formed later. For example, consider a mafic rock inclusion within a granitic rock.

The mafic rock formed first as magma cooled quickly; later, a change in magma chemistry led to the slower cooling and the subsequent formation of the surrounding coarse-grained granite. Hence, the granitic rock is younger and has formed around the already existing mafic inclusion. Understanding this principle helps geologists and students determine the chronological order in which geological events took place, assisting in piecing together the complex history of Earth's geology.