Fossil correlation is a method used by geologists and paleontologists to date and compare rock layers based on the fossils they contain. By identifying and matching similar fossils found in different locations, scientists can establish a timeline of Earth's history and understand how different species evolved over time. This technique relies on the principle that certain fossils, known as index fossils, are characteristic of specific geological periods. This approach helps in reconstructing past environments and understanding the distribution of life on Earth. Fossil correlation is essential for creating geological maps and for studying events like mass extinctions, which can be linked to changes in the planet's climate or geography.