Wikipedia:Today's featured article/April 12, 2019
Allison Guyot is an undersea volcanic mountain with a flat top in the Mid-Pacific Mountains. West of Hawaii and northeast of the Marshall Islands, it rises 1,500 metres (4,900 ft) above the seafloor to a platform 35 by 70 kilometres (22 mi × 43 mi) wide. It was probably formed by a hotspot before plate tectonics moved it north to its present-day location. Radiometric dating puts the formation of a volcanic island at around 111 to 85 million years ago. The island was eventually buried, forming an atoll-like structure and a carbonate platform. The platform emerged above sea level at some time in the Albian or Turonian ages before eventually drowning about 99 million years ago for unknown reasons; it is possible that the emergence damaged its reefs. After a hiatus lasting until the Paleocene, pelagic sedimentation deposited limestone, ooze and sand, which bear traces of climatic events and ocean currents. (Full article...)