Isostatic Rebound (Post-Glacial Rebound) is the term used to describe the ‘springing back’ of the Earth’s crust following deglaciation. Even today, many thousands of years after the last Ice Age we can detect this ‘rebound’ continuing. In parts of North America this has been measured at up to half an inch per year although this must be seen as somewhat exceptional. After the last Ice Age, parts of what is now southern and western Finland were under water but as the crust began to rise land rose above sea level and is still doing so today. Since the rate of rebound is known, archaeologists have been able to use the process to date prehistoric sites in the region. There are a number of useful website that explain the process(a)(b).