Glaciated Rocks are rocks

Rock (geology)

In geology, rock or stone is a naturally occurring solid aggregate of minerals and/or mineraloids.The Earth's outer solid layer, the lithosphere, is made of rock. In general rocks are of three types, namely, igneous, sedimentary, and metamorphic...

 which show evidence of having been exposed to a glacier

Glacier

A glacier is a large persistent body of ice that forms where the accumulation of snow exceeds its ablation over many years, often centuries. At least 0.1 km² in area and 50 m thick, but often much larger, a glacier slowly deforms and flows due to stresses induced by its weight...

. Generally they show striations or deep scratches, caused more by the debris being carried by the glacier than by the ice itself. Glaciated rocks may also be , erratics - that is, not belonging to the local rocks but having been transported there by the glacier.

Where a present day glacier is retreating, its former extent can be measured by distribution of the glaciated rocks. More significantly glaciated rocks in any area mean that it has been under ice at some stage. Thus they have produced evidence that Saudi Arabia

Saudi Arabia

The Kingdom of Saudi Arabia , commonly known in British English as Saudi Arabia and in Arabic as as-Sa‘ūdiyyah , is the largest state in Western Asia by land area, constituting the bulk of the Arabian Peninsula, and the second-largest in the Arab World...

was once covered by an ice sheet.