Organic metamorphism-kerogen-to-hydrocarbon transformation-is a function of both temperature and exposure time. The effect of temperature is exponential of that of time linear. At very low temperatures (<122 degrees F; <50 degrees C), the conversion rate is so low that time has no effect, since even long time spans of 300 to 500 Ma cannot compensate for this factor. At high temperatures (>266 degrees F;>130 degrees C) the reaction proceeds at such a high rate that time also plays no important role. The effect of time is noticeable in the range of 158 to 212 degrees F (70 to 100 degrees C), where intermediate conversion rates prevail. Stopping the heating process (termination of burial) freezes the rate-constant of the reaction and allows organic metamorphism to continue at a linear rather than exponential rate. This effect is demonstrated with the help of a simple geologic model. For the first example, a source rock was subjected to continuous linear heating, whereas, for the second, the heating was terminated at a certain temperature level. The model was analyzed by using the oleum scale, a modified Lopatin approach.--Journal abstract.