Classifica o e tipologia dos lapiás. Contributo para uma terminologia das formas cársicas.

Classification and types of karren. A contribution for a karst landforms terminology. The bibliography that refer to the forms developed in limestone rocks normally emphasizes the so called major karst forms (sinkholes, uvalas, poljes and fluvio-karstic forms), paying less attention to the so called minor karst forms, that are formed by the karren ones. In this particular field, the bibliography available in Portuguese is no exception. Hence the option of choosing this set of forms amongst all the wide range of karstic landforms, in addition to the fact that these smaller forms show better the existence of active dissolution processes at the surface that contribute decisively to the hydrologic underground karst activity. Most of the karren classifications are essentially descriptive favoring the morphology (forms and microforms), which leads to a multiplication of terms conferring a secondary role to the genesis and processes related to its formation. Therefore, we tried to develop a methodology to classify the karren and the related type of forms based on the formation processes that includes the type of sediment cover and the morphology. We consider three major groups of karren: i) those in which the dominant process (associated to dissolution) is related to running water; ii) those formed by the combined action of the runoff and of dissolution controlled by structural factors; iii) those with a mostly biochemical genesis, resulting from the action of dissolution (due to the persistence of water in flattened surfaces) and of the living organisms.