Some cosmic ray particles reach the surface of the earth and contribute to the natural background radiation environment.
It was discovered about a decade ago that cosmic ray interaction with silica and oxygen in quartz produced measurable amounts of the isotopes Beryllium-10 and Aluminium-26.
Cosmogenic nuclides are rare nuclides that form in surface rocks because of bombardment by high-energy cosmic rays.
Spallation reactions occur in minerals in the rocks upon bombardment by cosmic rays.
By sampling the rocks and separating certain minerals (such as quartz or pyroxene) and calculating the amount of these minerals (as a ratio to other, stable, minerals), we can work out how long the rock has been exposed on the earth’s surface.
Southern Mendoza, Argentina, is characterised by abundant Pleistocene to Holocene volcanism associated with back-arc magmatism, influenced by the subducting Nazca plate.
Age determinations in this volcanic area have been improved during the last 5 years.
Surface exposure age dating requires intensive chemistry.
Our samples are now pre-treated at the University of Canterbury.In rock and other materials of similar density, most of the cosmic ray flux is absorbed within the first meter of exposed material in reactions that produce new isotopes called cosmogenic nuclides.At Earth's surface most of these nuclides are produced by neutron spallation.The youngest age acquired is significant as it supports previous evidence for mid Holocene volcanic activity in the PVF and constitutes the first noble gas cosmogenic surface exposure age obtained from a basaltic bomb. | Using cosmogenic nuclides in glacial geology | Sampling strategies cosmogenic nuclide dating | Difficulties in cosmogenic nuclide dating | Calculating an exposure age | Further Reading | References | Comments | Cosmogenic nuclide dating can be used to determine rates of ice-sheet thinning and recession, the ages of moraines, and the age of glacially eroded bedrock surfaces.Cl analysis of 38 rock surfaces found in different glacial landforms in Denmark.