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All anomalies encountered so far either emit radiation or secrete a compound from within the soil or rock of the anomaly. This has a variety of effects on plant or animal life, or physical effects to people or objects within the sphere of influence.
Despite many being radiation based, all borders of anomalies seem to be clear and distinct, with the relevant radiation or chemical not straying past those borders. In a few instances, plant or animal life that has been affected has travelled beyond the borders.