Landslides along the Black Sea region in Turkey are frequent. The rapid increase in population and the consequent increased scarcity of land has been forcing the utilization of problematic areas for urbanization. These areas must be observed continuously and probable landslides must be determined beforehand. The use of inclinometers is the most commonly accepted and reliable monitoring method for assessing areas at risk of landslides. However, this method has the drawback of requiring demanding and long-term measurements. In this study, comprehensive investigations were carried out to determine the performance of the pressuremeter test for in situ measurement methods to expeditiously estimate the position of the slip surface. A sliding area on the Karadon Formation in Kozlu County, Zonguldak, Turkey was chosen for investigations. Observations and topographic measurements performed to assess the failure mechanism, and the obtained results specified that the movement type was a circular sliding. The in situ test results revealed that, the failure zone determined using the pressuremeter tests was in good agreement with the failure depths determined by inclinometer measurements.