IB ESS HL 3.1.16 (HL)—Geological epochs Question Bank

• Earth history is divided up into geological epochs according to the fossil record

• The geological timescale is divided into eons, which are further classified into eras, periods and epochs

• Changes in these time frames are marked by major geological and biological events

• The division between one epoch and the next is marked by significant changes in fossils, indicating environmental changes causing many extinctions