Glacial polish is a characteristic of rock surfaces where glaciers have passed over bedrock, typically granite or other hard igneous or metamorphic rock. Moving ice will carry pebbles and sand grains removed from upper levels which in turn grind a smooth or groved surface upon the underlying rock. The presence of such polish indicates that the glaciation was relatively recent (in geologic time scale) or was subsequently protected by deposition, as such polish will be subsequently lost due to weathering processes (such as exfoliation). Quarrying granite for the Mormon Temple, Utah Territory. ... Volcanic rock on North America Plutonic rock on North America Igneous rocks are formed when molten rock (magma) cools and solidifies, with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks. ... Metamorphic rock is the result of the transformation of a pre-existing rock type, the protolith, in a process called metamorphism, which means change in form (from the Greek prefix meta, after, and the noun morphe, form). The protolith is subjected to heat (greater than 150 degrees Celsius) and extreme... // The geological time scale is used by geologists and other scientists to describe the timing and relationships between events that have occurred during the history of the Earth. ... Geological exfoliation of granite at Enchanted Rock State Natural Area, Texas, USA Exfoliation in geology is a weathering process, mainly caused by freeze-thaw cycles. ...