41. The church was built from Silesian granite and glacial erratics , covered with a patterned slate roof cladding. 42. Because haystacks are identical to the local bedrock, they by definition cannot be classified as glacial erratics . 43. A few glacial erratics stud the prairie. 44. Geologically, the rock comes from Canada and is the largest glacial erratic rock in the Willamette Valley. 45. Because of the lack of large rock faces in Denmark and Northern Germany, glacial erratics were used instead. 46. In the syenitic glacial erratic boulder. 47. Plymouth Rock is a glacial erratic . 48. These have created the sand ridges of the geest with their typical glacial erratic boulders of granite and gneiss. 49. Snowdon and its surrounding peaks have been described as " true examples of roches moutonn�es, glacial erratics and moraines. 50. Larger pieces of rock that are encrusted in till or deposited on the surface are called " glacial erratics ".
