Bell Work What does "geology" mean?
To organize the vast number of years into manageable periods, scientists created a geologic time scale The geologic time scale is a record of the geologic events and the evolution of life forms as shown in rock and fossil records Scientists developed this scale by studying the rock layers, determining the relative ages and then placing them in order by relative age
The Geologic Time Scale
Scientists discovered rock layers are the result of major changes Fossils were used to provide evidence to the major changes taking place on Earth Geologic time begins with a long span of time called the Precambrian time, and very few fossils survive from this time
Dividing Geologic Time
Geologists divide time between the Precambrian and the present into three long units of time called eras Paleozoic Era Mesozoic Era Cenozoic Era
The Geologic Time Scale
What do you think is the most interesting part of the Geologic Time Scale?
- The time periods
- The kinds of fossils found
- The amount of time that has passed
- Other
Eras are subdivided into periods Each period is defined by certain events
Periods
During the first part of the Paleozoic Era, known as the Cambrian Period, like took a big leap forward Many different kinds of organisms evolved and this event is referred to as the Cambrian explosion At this time, all animals lived in the sea, and many did not have a backbone
The Cambrian Explosion
Draw a squirrel playing guitar in a bush