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 into the increasingly arid Bushmanland towards the north-west. To the north and north-east, it fades into the savannah and grasslands of Griqualand West and the Highveld. The boundary to the east grades into the grasslands of the Eastern Midlands. The Great Karoo is itself divided by the Great Escarpment into the Upper Karoo (generally above 1200–1500 m) and the Lower Karoo on the plains below at 700–800 m. A great many local names, each denoting different subregions of the Great Karoo, exist, some more widely, or more generally, known than others. In the Lower Karoo, going from west to east,