Trimlines can therefore also be used to reconstruct past ice sheet thickness.
However, this can be difficult, as thermal boundaries within the ice sheet may mean that it is more erosive lower down than higher up, and that cold, non-erosive ice on the tops of mountains may leave in tact older landscapes.
When it reaches the terminus of the glacier, the boulder will be deposited.
Glacial geologists are often interested in dating the maximum extents of glaciers or rates of recession, and so will look for boulders deposited on moraines.
This is important for glacial geologists, as it means that surfaces that have had repeated glaciations with repeated periods of exposure to cosmic rays can still be dated, as long as they have had sufficient glacial erosion to remove any inherited signal.
Glacial geologists use this phenomenon to date glacial landforms, such as erratics or glacially transported boulders on moraines or glacially eroded bedrock.
Once exposed to the atmosphere, the boulder will begin to accumulate cosmogenic nuclides.
Assuming that the boulder remains in a stable position, and does not roll or move after deposition, this boulder will give an excellent As well as using cosmogenic nuclide dating to work out the past extent of ice sheets and the rate at which they shrank back, we can use it to work out ice-sheet thicknesses and rates of thinning[5, 6].
For most of the samples collected along the main flowpath, a significant decay effect was observed.
An attempt of dating was made by using an equation that takes into account radioactive decay of the meteoric–epigene input, deep production and chloride dissolution within the aquifer.
The calculated Cl residence time varies from 16 to 500 ka for the minimum ages, and from 25 to 1200 ka for the maximum ages.
Several factors can affect cosmogenic nuclide dating: rock type, attenuation of cosmic rays, topographic shielding, post-depositional movement, and burial and cover by snow, vegetation or earth.
Geologists must ensure that they choose an appropriate rock.