Photographs taken by rail staff have revealed the depths of snow that have affected the Far North Rail Line and disrupted services to Wick.
Network Rail released the images to SNP MSP Rob Gibson after he asked why trains between Inverness and Wick have been so badly hit.
A snow plough has been operating on the line.
But the engine has been stopped by deep drifts at Forsinard about 100 miles (160.9km) from Inverness.
In its reply to Mr Gibson, Network Rail said: "The problems experienced recently on the line are due to the volume of snow over an extended period of time.
"We do plough the lines and across Scotland we have 10 snow ploughs with half of those dedicated to the north.
"Despite the ploughs being fully in operation it has still proved difficult to keep the line clear of snow, partly due to fresh snowfalls and partly due to drag from trains pulling snow onto the line."
Network Rail added that snow-laden trees had also fallen on the line.
Mr Gibson praised the efforts of rail worker to clear the track.
He said: "It seems that sheer weight of snow and fallen trees have prevented it.
"The weather has been particularly bad in the north and as the pictures show there is a great deal of snow to shift as well as the problems of falling trees.
"I was concerned about the prolonged closure of the route but am sure that Network Rail are doing all they can to open the line."