A more thorough explanation:

A natural monument is a non-artificial permanent object on land, such as a tree, river, or beach. It is also referred to as a natural object.

For example, the Grand Canyon is a natural monument because it is a permanent feature of the land that was not created by humans. Another example is the Giant Sequoia trees in California, which are natural monuments because they are non-artificial and have been around for thousands of years.

These examples illustrate the definition of a natural monument because they are both non-artificial and permanent features of the land. They are not man-made structures or objects, but rather natural wonders that have been around for a long time and will continue to exist for many years to come.