A soil type of bright red or brown-red colour of clay or clay, occurring mainly in the Mediterranean area (Southern Europe, North Africa, Near East and partly also in the USA). The red colour is caused by the high proportion of the iron compound haematite (bright iron ore). Often it lies directly above a water-permeable limestone layer and is therefore also known as limestone red clay. It is a phenomenon in karst areas, it is assumed that undisturbed rendzines will develop into Terra Rossa soils in the long term. Soil formation processes already took place in the Tertiary 15 million years ago and consisted of the leaching of the limestone components when the clay minerals and other mineral impurities such as red iron compounds contained in the limestone were left behind. However, more recent research also suggests a much more recent history of formation, as the input of red mineral dust from the Sahara and Sahel region, which is at most 25,000 years old, has been proven.