Image segmentation is a critical step in image analysis, and generally involves a high computational cost, especially when dealing with large volumes of data. Given the significant increase in the spatial, spectral and temporal resolutions of remote sensing imagery in the last years, current sequential and parallel solutions fail to deliver the expected performance and scalability. This work proposes a distributed image segmentation method, capable of handling very large high-resolution images in an efficient and scalable way. The proposed solution is based on the MapReduce model, which offers a highly scalable and reliable framework for storing and processing massive data in cluster environments and in private and public computing clouds. The proposed method is extendable to any region-growing algorithm and can be adapted to other models. The solution was implemented and validated using the Hadoop platform. Experimental results attest the viability of performing distributed segmentation over the MapReduce model through cloud computing.