Spirku Bog
Spirku Bog is a raised bog about 17 km north-eastwards from Ludza; on the Zilupes valley.
Area: 737 ha
The average depth of the peat layer is 1.9 m; the deepest layer is at 3.7 m.
Total deposit of peat: 14 mil. m3
Up to 1 m peat is little decayed; deeper it is medium and well decayed. About 1.5 km westwards the Ludza River outflows from the bog. The bog is overgrown with sparse pine trees.
Latvijas daba. 5.sēj. – Rīga: Latvijas enciklopēdija, 1998. – P.145.