GENERAL GEOLOGY

Detailed explanation-1: -Five major mass extinctions are recognized: Late Ordovician, Late Devonian, Late Permian, Late Triassic, and Late Cretaceous (Figure 6.27).

Detailed explanation-2: -The ‘Big Five’ mass extinctions There have been five mass extinction events in Earth’s history. At least, since 500 million years ago; we know very little about extinction events in the Precambrian and early Cambrian earlier which predates this.

Detailed explanation-3: -The fifth period of extinction happened around 65 million years ago and is more popularly known as Cretaceous-Tertiary extinction.

Detailed explanation-4: -Sea-level falls are associated with most of the mass extinctions, including all of the “Big Five"-End-Ordovician, Late Devonian, End-Permian, End-Triassic, and End-Cretaceous, along with the more recently recognised Capitanian mass extinction of comparable severity to the Big Five.

Detailed explanation-5: -Ordovician-silurian Extinction: 440 million years ago. Devonian Extinction: 365 million years ago. Permian-triassic Extinction: 250 million years ago. Triassic-jurassic Extinction: 210 million years ago. Cretaceous-tertiary Extinction: 65 Million Years Ago.