Part 1: Geology

Section 1: Introduction

Geologic Calendar

Geologic Time Table

Figure 1. Geologic Time Table. The geologic calendar is divided into four major time periods called eras. (SHSND-ND Studies)

GeologyThe scientific study of the earth is the science that works to understand planet Earth. GeologistsScientists who study the earth are scientists who study Earth’s history. Geologists study rocks and other materials that make up the planet and the geologic processes that affect Earth today.

Paleontology• Study of the history and life on Earth.
• Study of fossils.
is the study of prehistoric life. PaleontologistsScientists who study fossils are scientists who study fossils to determine what life was like on Earth at different times in the geologic past. Paleontologists must understand the behavior and habitats of living species in order to understand how extinct (all are gone) species lived.

Have you ever tried to guess Earth’s age? Scientists estimate Earth is about 4.5 billion-years-old – give or take a few hundred million years! This huge span of time is called Geologic Time.• Divides Earth’s history into time periods.
• Indicates big changes that took place on Earth.
• Constantly being refined.

Geologists have worked out a type of calendar called a geologic time table that indicates when big changes took place on Earth. Beginning about 1820, a “calendar” called Geologic Time Scale was developed, and is still being refined.

This geologic calendar is divided into four main time periods called eras.The four longest divisions of geologic time The four eras are Precambrian, Paleozoic, Mesozoic, and Cenozoic.