Other Possible Causes of The Cat Gap
Volcanic activity has also been promoted as a possible cause of the cat gap as well as other extinctions during this time period. The La Garita Caldera is a large volcanic caldera located in the San Juan Mountains in southwestern Colorado, United States, and is one of a number of calderas that formed during a massive ignimbrite flare-up in Colorado, Utah, and Nevada during the Oligocene Epoch. The La Garita Caldera was the site of the Fish Canyon eruption, an enormous eruption about 27 million years ago. The scale of the Fish Canyon eruption was far beyond anything known in human history (erupting more than 10,000 km3 or 2,400 cu mi for a VEI 8+ magnitude), and was possibly the most energetic event on Earth since the Chicxulub impact, which is thought by many paleontologists to have caused the extinction of the dinosaurs in the Cretaceous–Paleogene extinction event. The resulting explosive volcanism probably ejected large amounts of dust and debris into the stratosphere causing major cooling (see volcanic winter). Climatic effects could also have been caused by sulphur ejected into the stratosphere, which rapidly converts to sulphuric acid, an aerosol which cools the troposphere by blocking incoming solar radiation.
Another possible cause of the cat gap could have been the late Cenozoic ice age that began approximately 30 million years ago. This ice age caused glaciation in Antarctica that eventually spread to Arctic regions of southern Alaska, Greenland, and Iceland. Glaciers on the North American continent, as well as the cooling trend, could have made the ecosystem uninhabitable for feliformia cat-like species, although habitable for cold-weather caniformia species such as canids (dog-like species), mustelids (weasel-like species), and ursids (bear-like species).
| “ | There is also evidence that during the Miocene a sill surrounding the Arctic Ocean, known as the Greenland–Scotland Ridge, subsided, allowing more cold polar water to escape into the North Atlantic. As the salinity of the North Atlantic grew and as outflow of cold polar water increased, so the thermohaline circulation increased in vigour, providing the mild winter temperatures and large amounts of moisture to the North Atlantic, which are prerequisites to the build-up of the large continental ice caps on the adjacent cold continents. | ” |
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