The Cretaceous–Paleogene (K–Pg) boundary, formerly known as the Cretaceous–Tertiary (K–T) boundary, is a geological signature, usually a thin band of rock containing much more iridium than other bands. The K–Pg boundary marks the end of the Cretaceous Period, the last period of the Mesozoic Era, and marks the beginning of the Paleogene Period, the first period of the …

An extinction event (also known as a mass extinction or biotic crisis) is a widespread and rapid decrease in the biodiversity on Earth.Such an event is identified by a sharp change in the diversity and abundance of multicellular organisms.It occurs when the rate of extinction increases with respect to the rate of speciation.Estimates of the number of major mass extinctions in the last …

The Cretaceous–Tertiary extinction event, now called the Cretaceous–Palaeogene extinction event, was about 65.5 million years ago. It may be called the K/T extinction event or K/Pg event for short. This is the famous event which killed most of the dinosaurs at the end of the Cretaceous period.. It was a large-scale mass extinction of animal and plant species.