 The wood used to build the track is now classed as bog @-@ wood , the name given to wood ( of any source ) that for long periods ( sometimes hundreds of thousands of years ) has been buried in peat bogs , and kept from decaying by the acidic and anaerobic bog conditions . Bog @-@ wood is usually stained brown by tannins dissolved in the acidic water , and represents an early stage of fossilisation . The age of the track prompted large @-@ scale excavations in 1973 , funded by the Department of the Environment . 
