Measure peat depth by pushing a long rod down until it meets the firm mineral soil beneath, repeated on a grid across the bog. Under 50 cm is marginal, 50-200 cm is a workable fuel source and over 200 cm is a major resource, and the average depth times the area gives the volume you can plan from.
Part of Peat Harvesting
Probing a bog to find how deep the peat is, mapping it, and turning depth into a volume.
Depth Is Supply
The parent article gives the classes: less than 50 cm is marginal, mostly low-quality surface peat; 50-200 cm is workable; more than 200 cm is a major resource of years or decades of fuel.
What You Need
- A rod, metal or a straight stick, longer than the likely depth. A T-handle makes pulling it out easier.
- A marked scale on the rod, in centimetres.
- Stakes and a tape or knotted cord to lay out a grid.
- A partner and a rope.
Method
Step 1: Lay a grid. Stake lines across the bog at an interval you can manage; 10 m is a sensible start for a small bog, and closer where depth changes quickly.
Step 2: Probe each point. Push the rod down steadily. Peat offers a soft, even resistance. The mineral floor, usually clay, sand or gravel, feels firm and gritty, and the rod stops. Read the depth at the surface.
Step 3: Check false floors. Buried tree trunks and stumps stop a rod, and so can a hard layer inside the peat. Probe a metre to one side. If the depth changes by a large amount, you found a log.
Step 4: Draw it. Write the depths on a sketch of the grid and shade the contours of depth. The deep centre and thin margins show where to cut.
Step 5: Estimate the volume. Average depth × area. For example, 2 m × 10,000 m² (one hectare) = 20,000 m³.
Worked Example: A Small Bog
Inputs: probe depths of 1.2, 1.8, 2.2, 2.0, 1.6 and 0.8 m at six grid points, each standing for 1,000 m² (an assumption for the example).
- Total of the depths = 1.2 + 1.8 + 2.2 + 2.0 + 1.6 + 0.8 = 9.6 m.
- Mean depth = 9.6 ÷ 6 = 1.6 m.
- Volume = 1.6 m × 6,000 m² = 9,600 m³.
By the parent’s classes this bog is workable (1.6 m is between 0.5 and 2 m), but not yet a major resource.
Common Mistakes
- Stopping on the first hit. It may be a log, a boulder or a buried hard layer.
- Probing too few points. Bog floors are uneven.
- Counting the whole depth as fuel. The surface 10-20 cm turf and the last 10-20 cm above the mineral base are left (parent), as covered in Cutting Technique & Block Sizes.
Safety
Probing means walking on unproven ground
Work from firm ground outwards, test each step with the pole, and keep a partner at the edge with a rope. Do not probe where the surface quakes or where black water shows through the moss. A rod pushed hard can pull a person off balance when it is released: keep your footing.
What’s Next
- Learn next: Cutting & Extraction — taking the peat
- Combine with: Sustainable Harvesting Limits — how much to take