Bivariate mountain definition: a case study for the turkish mountain system 

Türkiye, 61% of which consists of mountains, has an extremely rugged topography. Anatolia, which is located in the collision zone of plates with different characteristics, exhibits a morphological character with different stages of mountain formation due to the Paleotectonic and Neotectonic movements it has been exposed to during geological times. In Anatolia, where the main physiographic character is mountains, the proportion and boundaries of mountains and mountainous areas have not been quantitatively defined and there has not been a geomorphometric approach to this until now. In this study, the mountain definition obtained from the pixel-based and multi-scale basic data matrix was subjected to various analyzes with the modeling created in geographic information systems. In addition, how the mountain definition and classification change at varying scales and thresholds is revealed. The characterization has two main purposes: To determine the framework of the methodology in the definition of macro landforms and to determine the most optimum model that quantitatively defines mountain and mountainous area. According to the model, mountains cover 61% of Türkiye. In this context, in addition to developing a model to geomorphometrically define mountain and mountainous area characterization, the thesis approaches mountains, which are a macro morphological landform, from an ontological perspective and approaches the questions we asked at the beginning in terms of geographical epistomology. In this respect, the thesis is a contribution to traditional geomorphology.  A bivariate map of 16 classes to visualize the relationships between morphological variables and a combination of mean elevation and topographic relief classifies mountains. The classification shows a transition from low rugged and low mountains, to moderate rugged and moderate height mountains, to high rugged and high mountains, to very high rugged and very high mountains. Within the framework of the classification, according to four different ruggedness ratios in Türkiye, low rugged mountains occupy 37%, moderate rugged mountains 33%, high rugged mountains 20% and very high rugged mountains 9%.