The extant main islands of the archipelago have been above the surface of the ocean for fewer than 10 million years; a fraction of the time biological colonization and evolution have occurred there. The islands are well known for the environmental diversity that occurs on high mountains within a trade winds field. On a single island, the climate around the coasts can range from dry tropical to wet tropical; on the slopes, environments range from tropical rainforest , through a temperate climate, to alpine conditions with a cold, dry climate. The rainy climate impacts soil development, which largely determines ground permeability, affecting the distribution of streams and wetlands.
Highland Traditions of Scotland
The region became culturally distinguishable from the Lowlands from the later Middle Ages into the modern period.