The type of erosion caused by deep gouges and scratches on bedrock in an area once covered by a glacier is called glacial striations.

Here's why:

* Glaciers are powerful agents of erosion: Their immense weight and slow movement allow them to carve through bedrock, carrying away rock fragments and debris.

* Striations are characteristic marks: The embedded rocks and debris within the glacier scrape against the bedrock, creating long, parallel scratches known as glacial striations.

* Direction of movement: These striations provide valuable information about the direction the glacier was moving.

So, the geologist's discovery of deep gouges and scratches on bedrock is strong evidence of past glacial activity and the erosive power of glaciers.