The basic rocks of Chrissi were created by the solidification of lava, ejected by an underwater volcano millions of years ago. While walking around the island, visitors will be impressed by the colors of the rocks (reddish brown, greenish gray and black).
The larger part of the island is covered by sand. On the flat areas the ground is relatively solid and consists of fine reddish sand, mainly covered by moss and lichens. At the areas where there are sand dunes, the sand is yellow and course. The sand is mainly supported by the complex underground roots of the cedars and their leaves, which actually touch the ground.
The vegetation is quite diverse in view of the island’s size. There are mainly cedars, junipers, lentisc, thyme, heath and rockroses and sandy shore vegetation. The Cedar forest of Chrissi is very rare in its expanse and structure. It covers almost 35 hectares and its density is approximately 28 trees per hectare.
Their average height is 3 to 7m tall and their average age is at least 300 years old. Cedars have a root system that spreads across an area which is more than double the height of the tree.
Apart from the big roots, a huge amount of tiny roots forms a complex web that keeps the sand in place. The number of plant species of Chrissi is relatively high compared to its size, comprising 1/20 of the Cretan flora. Many species are rare and endemic, therefore protected by international directives and laws.
In the sea around Chrisi the variety and abundance of the marine species are impressive, as the water is shallow.
The sea bed around the island up to a depth of 20m covers about 30km2 (area six times the size of the island).Most of the island’s animal species have a Mediterranean distribution. None of them pose any threat to humans.