That Great Britain and Italy belong to distinct regional geological domains is a matter of basic geographic and geological fact, requiring no citation.
The claim states a fundamental, self-evident geographic and geological fact: Great Britain and Italy are located in entirely separate regions of Europe and belong to different geological frameworks (e.g., British Isles shelf versus the Alpine-Mediterranean tectonic systems of Italy). Under STEP 0, statements that are trivially true by direct everyday observation or basic geographical definition are common knowledge and require no citation.