41. A thin layer of this alga tends to cover rock surfaces and seaweeds grow as epiphytes on top. 42. As it crawls across a rock surface , pieces of its base become detached and grow into new individuals. 43. Tsogt Taiji composed his popular poem in 1621 which was later written on a rock surface in 1624. 44. As a result, several rocks surfaced which were barely visible and often covered in small pools of water. 45. The next advancement in the history of communications came with the production of petroglyphs, carvings into a rock surface . 46. The Mars scientific exploring machine Spirit has observed case hardening present of the rock surface present at Gusev meteorite Crater. 47. In that regard, Kerridge noted that the rock surface has a fragmented texture suspiciously like that of the so-called fossil. 48. It is on this crystalline rock surface that the younger, more familiar layered rocks of the Colorado Plateau were deposited. 49. Generally it is located on rock surfaces rather than under stones, and is often found above neap high water mark. 50. Inside the Reserve there are at least 420 rock surfaces with rock engraves declared in 1979 World Heritage by UNESCO.
