A trap hill has several visually distinctive features that make it recognisable without any geological training.

Shape

The most immediately noticeable feature is the stepped or terraced profile — a staircase-like appearance on the slopes. This is the origin of the name, from the Swedish word trappa, meaning staircase. The steps form because the rock weathers and breaks along regular joints and fractures in the dolerite, producing roughly horizontal ledges or benches on the hillside.

Rock

The exposed rock itself stands out. Dolerite is dark — grey to almost black — which contrasts sharply with the pale, often reddish or ochre-coloured soils and granites of the surrounding Yilgarn landscape. Blocky, angular dark boulders and outcrops on or around the hill are a strong indicator.

Vegetation

Trap hills often carry noticeably different vegetation from the surrounding country. The dolerite weathers to a heavier, more fertile soil that retains moisture better than granitic soils, so the hill may support denser or taller scrub, different species, or greener growth — particularly visible in dry seasons when the contrast with surrounding country is most pronounced.

Prominence

Because dolerite is harder and more resistant than the surrounding granite or sedimentary rock, trap hills tend to stand as distinct, elongated ridges or isolated rises above the general level of the landscape — often running in a roughly straight line, reflecting the linear geometry of the original sill or dyke.

Together, the dark stepped rock, the linear ridge form, and the contrasting vegetation make a trap hill quite recognisable once you know what to look for.