Valley of the Kings rains. There is currently little year-round rain in this part of Egypt, but there are occasional flash floods that hit the valley, dumping tons of debris into the open tombs. The quality of the rock in the Valley is inconsistent, ranging from finely-grained to coarse stone, the latter with the potential to be structurally unsound. The occasional layer of shale also caused construction and conservation difficulties, as this rock expands in the presence of water, forcing apart the stone surrounding it. It is thought that some tombs were altered in shape and size depending on the types of rock the
Exploration of the Valley of the Kings Period tombs in the main valley. Various expeditions have continued to explore the valley, adding greatly to the knowledge of the area. In 2001 the Theban Mapping Project designed new signs for the tombs, providing information and plans of the open tombs. On February 8, 2006, the Supreme Council of Antiquities announced that an American team led by the University of Memphis had uncovered a pharaonic-era tomb (KV63), the first uncovered there since King Tutankhamun's in 1922. The 18th Dynasty tomb included five intact sarcophagi with coloured funerary masks along with 28 large storage jars, sealed with pharaonic seals. It