The underlying rock of the Strathconon DMG is largely acidic Moine pelitic schist and gneiss, with restricted occurrences of siliceous schists and granulites in the east. Less acidic outcrops of epidiorite and hornblende schists occur in a few places, particularly around Carn Ban. The main landforms were modified by glacial activity during the Devensian glaciation (and to a lesser extent the Loch Lomond interstadial). This comprises a plateau dissected by west-east ‘U’ shaped glaciated valleys with corries and ribbon lochs. The anomaly of the Meig valley sector between Inverchorain and Milton (running SSW-NNE) marks a line of weakness associated with the Strathconon Fault which runs sub-parallel with the Great Glen Fault area extends from farm land touching the Cromarty Firth in the south east.

Soils are dominated by peat which forms a blanket over the solid geology and much of the glacial material, apart from on very steep slopes and at higher altitudes. These peats are nutrient poor and vegetation is unable to gain access to the parent material under the peat. Better soils occur on the main valley floors where alluvial gravels, sands and silts are deposited and on some slopes where drainage is better. The range of semi-natural habitats in the Management Area is thus generally rather nutrient poor, reflecting a cool, wet climate, base-poor geology, peat soils and to some extent, past deforestation, burning and grazing.