Chapter 1, Problem 1RQ

To determine

The use of actualism in geology to interpret ancient rocks with the help of some general examples.

Answer to Problem 1RQ

Actualism is a concept used by geologists to interpret the ancient rocks. For example, geologists can assume that ancient rocks are of volcanic origin as they closely resemble those forming today by volcanic eruptions of molten rock.

Explanation of Solution

Actualism is the term used by geologists. It is a main principle of science, and it applies on all time scales. It is an idea which states that the facts of geology can be explained in terms of physical and chemical processes that have operated throughout Earth’s history.

General examples of the use of actualism to interpret ancient rocks are as follows:

(i) Aeolian sandstone resembles the properties of lithified aeolian sand. A geologist can say that they are formed in the same way that similar ripples developed recently under the influence of certain kinds of wind or water movement. This can explain the interpretation of ancient rocks by using a known observable process.

(ii) The ancient rocks closely resemble the molten rocks forming recently due to volcanic eruptions in Hawaii. The geologists can assume that the ancient rocks are also the result of volcanic eruptions.