8.6 - Geologic Time Scale

The Geologic Time Scale is a record of ________________.

• famous geologists throughout history

• geologic events and life forms throughout Earth's history

• a list of every living thing ever

How old do paleontologists believe the Earth is?

• 2019 years old

• 3.5 million years old

• 4.6 billion years old

Why is the fossil record incomplete?

• fossils get eroded away over time
• most organisms never became fossils
• scavengers and decomposers eat them too quickly
• all of the above

Paleozoic, Mesozoic & Cenozoic are all _____________ in geologic time.

• Periods

• Eras

Which is the most recent era of time- the one that we are currently in?

• Mesozoic 
• Paleozoic 
• Cenozoic 
• Precambrian 

Cambrian, Ordovician, Silurian, Devonian, Mississippian, Pennsylvanian, Permian, Triassic, Jurassic, Cretaceous, Tertiary, Quaternary are all examples of ___________________ in geologic time.

• Periods

• Eras

Which is the correct order for the 3 eras on the geologic time scale, from oldest to most recent.

• Paleozoic, Mesozoic, Cenozoic

• Mesozoic, Paleozoic, Cenozoic

• Cenozoic, Mesozoic, Paleozoic

Each of the three eras can be divided into smaller __________

• Periods

• Eons

Scientists chose where units of geologic time began based on major changes in ______________ at certain times.

• life forms

• climate

_______________ is the long span of time that begins geologic time.

• Precambrian Time

• Cenozoic Time