This is a photo I took of how the grade collapsed on the abandoned CNR Rossburn sub line . This line was built in 1904. The last train ran on this line in late March of 1996. This right of way is now part of the Trans Canada Trail system. This is 2 miles from where I live. The earth sank about 8 feet but did not slide sideways, just went straight down. This is something that just does not happen in this area. Any suggestions as to why this occurred?