This topic in depth deals with the Younger Dryas event, a short period of extremely cold temperatures interrupting the current interglacial period. It is currently debated whether the Younger Dryas event occurred solely in parts of the North hemisphere or throughout the world. The first website, (1), created by World History, provides a short, concise summary of the Younger Dryas period. Users can find a brief statement about the prevailing theory of the cause of this event. Lund University offers an amazing image of a stratigraphic record illustrating the Late Glacial sequence at the second website (2). Users can view the impressive Younger Dryas sedimentation layer and also see an image of the flower, _Dryas octopetala_, which the event is named after. Next, the Department of Natural Resources for the Province of Nova Scotia supplies images of the geologic landscape of Nova Scotia (3). Students can find descriptions of the Younger Dryas event and other glacial features. The forth website (4 ), produced by Klaus Keller as part of his lecture materials for classes at Penn State, is an online document illustrating the abrupt changes experienced on earth during the Younger Dryas. This website discusses the theorized relationship between the North Atlantic thermohaline circulation (THC) and the event. Next, the University of Arizona discusses its research on the environmental changes in mid-North America over the last several millennia (5). Users can learn how the researchers are attempting to create the first high-resolution chronology of the transition from the Late Glacial to the Early Holocene. In the sixth website (6 ), the University of Chicago offers an online article addressing the unknowns in our current understanding of climate change. Users can learn how the abrupt climate changes in the past such as the Younger Dryas are still difficult to model. Next, David J. Graham from the University of Wales addresses the importance of examining the moraine morphology and sedimentology in order to gather more knowledge about the climatic and glacio-dynamic conditions that occurred during the Younger Dryas period (7 ). This online poster provides images, figures, and descriptions of the interpretations of the landform-sediment associations present in the upper Ennerdale. Konrad Hughen from the Woods Hole Oceanographic Institution summarizes his group's research which illustrates the effects the northern tropical regions of the Southern Hemisphere experienced during the Younger Dryas event (8). In this downloadable document, users can learn about his group's creation of high-resolution records of tropical vegetation change that demonstrate the synchronization between the climate changes in the high latitude North Atlantic region and in the tropical South America during the event. Lastly, the U.S. Global Change Research Program discusses the classification of an abrupt climate change, the rapidity of past climate change according to the paleoclimatic records, the causes of climate change, and its consequences (9). Visitors can learn about the swiftness of the Younger Dryas event and how another occurrence like this may affect our society and the natural world.