Earths Natural Radiation Leak

20 December 2001

Most people don't know that the earth's rocks are leaking their own small amounts of radiation every minute of the day, every day of the year, and that Geoscience Australia is using that faint radiation to get a most unusual image of our continent.

Most rocks and soils contain minuscule amounts of radioactive elements. Over time these elements decay and release gamma-radiation into the surrounding ground or air. The amount of this radiation is very small - so small in fact that only the most sensitive instruments can detect it.

However, it is possible to measure the radiation being emitted from the rocks and soil on the earth's surface using an instrument mounted in a low flying aeroplane. The instrument can measure the radiation being emitted from the decay of three different elements -- potassium, uranium and thorium. Using the three recordings an unusual image of the earth's surface can be produced.

The image produced, known as a radiometrics image, is a picture of the radiation coming from the top few centimetres of the rocks and soil. Those areas rich in potassium, such as granite, appear with a pinkish glow. Those richer in thorium like river channels have a green glow and those richer in uranium have a blue glow.

These images can be used to get a greater understanding of the movement of materials at the earth's surface. They can help define ancient river channels as well as the mapping of salinity and land degradation. They can be used to discover mineral deposits and help define features such as faults. Because they can be produced by flying over an area, they provide a fast, effective and non-invasive way of looking at a region which can then be studied in greater detail by researchers in universities, government or industry.

While the 'glow' is artificial, the benefit of using techniques like this to study our country is certainly futuristic and can take the 'fiction' out of the science of our earth.

Topic contact: Last updated: October 4, 2013