We propose a new data model to represent dynamic and continuous geographic phenomena over spatiotemporal domain in moving-object databases. Existing data models of moving objects have shortcomings with respect to the representation of moving geographic phenomena involving continuous fields, such as temperature, elevation, and the degree of pollution. Moreover, in the case of a spatiotemporal model for continuous fields, it is difficult to deal with continuous movements through time. In this paper, we define a data type called moving field to represent both object-based and field-based views of geographic phenomena in spatiotemporal domains. The main feature of our model is that it integrates the spatial field model with the slice representation of moving objects. By introducing moving fields, we provide a new computational environment for analyzing various moving phenomena with numerical as well as geographic processing.