Chicxulub crater
Many scientists hypothesize that the Cretaceous–Paleogene extinctions were caused by catastrophic events such as the massive asteroid impact that caused the Chicxulub crater, in combination with increased volcanic activity, such as that recorded in the Deccan Traps, both of which have been firmly dated to the time of the extinction event. In theory, these events reduced sunlight and hindered photosynthesis, leading to a massive disruption in Earth's ecology. A much smaller number of researchers believe the extinction was more gradual, resulting from slower changes in sea level or climate.