Around 4,000 years ago the climate began to deteriorate and peat started to spread across the upland areas forcing people to move to the milder climate and fertile ground around the coast. Here they clustered together in small townships. It is thought that increasingly inhospitable weather impacted on food supplies and in turn on population size, and that there was also an increase in warfare. The arrival of bronze at this time gives its name to the archaeological period �?the Bronze Age.
Houses, field systems and a smithy have all been found on mainland Shetland and the settlements at Jarlshof and Scatness, both lying within a couple of miles of Sumburgh Airport, are essential viewing.
Crussa Field, Unst, has what may be a Bronze Age cremation cemetery called the “Rounds of Tivla�?�?3 rings of banks and ditches surrounding a stony central area.