A second peak, Porteous Hill, lies at the southern end of the Kilmog, rising to 395 m (1317 ft).
In the five kilometre stretch from Evansdale, at the northern end of Blueskin Bay, SH1 climbs from sea level to an altitude of 300 m — the highest point on the highway south of Amberley in north Canterbury.
The geology of the Kilmog is predominantly a basaltic intrusion into a raised section of the Otago peneplain, the latter mostly Cretaceous schist, over which is a deposit of sandstone with some quartz.
The instability of the land also led to the disgrace of architect Robert Lawson, whose Seacliff Lunatic Asylum was structurally affected, and to the replacement of a railway tunnel on the South Island Main Trunk line by a cutting.
[3] A narrow winding scenic alternative route bypassing the Kilmog follows the coast past the settlements of Warrington and Seacliff, but this is of a relatively poor standard and is not recommended for heavy vehicles.