Karoo Supergroup of the country, and in the Lebombo mountains along the Mozambique border. Once the layer of hard lava was eroded away, the softer Karoo sediments over the rest of the basin eroded even faster. However, the dolerite sills resisted erosion, protecting the softer Beaufort and Ecca shales beneath them. This created numerous and widespread flat topped hills, known as Karoo Koppies ("koppie" being the Afrikaans term for hill), which are iconic of the Karoo, and, by extension, the South African landscape. The dykes, or vertical fissures which brought the lava to the surface stand out today as linear ridges extending
Karoo sills (see below), creating multiple flat-topped hills, or Karoo Koppies, which are iconic of the Great Karoo. The vegetation of the Upper is similar to the Lower Karoo, so few people make a distinction between the two. The main highway (the N1) and railway line from Cape Town to the north enter the Lower Karoo from the Hex River Valley just before Touws River and follow a course about 50 km south of the Great Escarpment up to Beaufort West. Thereafter, they gradually ascend the Great Escarpment along a broad valley to Three Sisters on the Central Plateau and the