Geologists in Arctic Canada have found the fossil of a tropical freshwater Asian turtle. This suggests that animals migrated directly across a freshwater sea floating on top the warm salty Arctic Ocean from Asia to North America. This finding also suggests that a rapid increase of carbon dioxide about 90 million years ago created a greenhouse effect that created polar heat. Scientists studied lava flows that cover the High Arctic islands, and they concluded that volcanic events produced a series of islands along a underwater mountain range in the Arctic Ocean, which is called the Alpha Ridge. If the ridge poked above the surface of the water at one time, it would have allowed turtles and other animals to walk across the islands. They also believe that this volcanic rock contributed to creating the climate in which the turtles lived. The turtles lived on top of flood basalts, which leads scientists to believe that the warming may have been caused by volcanoes sending carbon dioxide into the atomosphere. They have evidence that this occured all around Earth and not just the Arctic, so if this happened over a short period of time, it would create a greenhouse effect all around the Earth.