efterstigning

Efterstigning, or postglacial rebound, is the ongoing rise of the land relative to the sea that follows the melting of large ice sheets at the end of the last glacial period. It results from the viscoelastic adjustment of the Earth’s lithosphere and the flow of mantle material back toward regions that were depressed under the ice load.

The mechanism begins when the ice sheet retreats and the crust, previously weighed down, begins to rebound. The rate and pattern of uplift vary by location and over time, with the strongest effects in areas that bore the heaviest ice. Typical uplift rates are on the order of millimeters to about a centimeter per year, and the process continues for thousands of years, gradually slowing as equilibrium is approached.

Regional patterns are pronounced. In Fennoscandia (Norway, Sweden, Finland), land has risen substantially since the last glacial maximum, leading to long-term changes in coastlines and inland drainage. In other formerly glaciated regions, such as parts of North America, similar rebound has occurred but with different spatial profiles. Because uplift reduces relative sea level locally while global sea level continues to change, some coastlines experience relative sea-level fall while others may still rise.

Measurements rely on GPS networks, tide gauges, and geological indicators to determine vertical land motion and sea-level change. These observations are used to model future coastline evolution, manage infrastructure, and reinterpret past sea-level records.

See also glacial isostatic adjustment.