Geologic TimeGeologic Time

Created By:Mr. KreegerCreated By:Mr. Kreeger

Homework and Page References

Homework and Page References Page References-Chapter 32

(pages 597-609)

Homework Handouts

Page References-Chapter 32 (pages 597-609)

Homework Handouts

Table of ContentsTable of Contents

Explanation of ESRT page 8 and 9 The Fossil Record Inferences of Fossil Evidence Index Fossils Key Beds

Explanation of ESRT page 8 and 9 The Fossil Record Inferences of Fossil Evidence Index Fossils Key Beds

The Geologic Time The Geologic Time TableTable

ESRT pg 8&9ESRT pg 8&9

Most all divisions on this table are Most all divisions on this table are based on life-events that have based on life-events that have

occurred in the pastoccurred in the past

Eras are divided based upon when dominant life Eras are divided based upon when dominant life forms existedforms existed

Cenozoic -- "Age of Mammals"Mesozoic -- " Age of Reptiles“Paleozoic -- " Age of invertebrates"

Periods usually begin or end based on a Periods usually begin or end based on a beginning or end of a certain type of animalbeginning or end of a certain type of animal

Jurassic Period began when Giant Dinosaurs were abundant.

Eras are the longest period of time on the table.

Usually hundreds of millions of years (except Cenozoic)

Periods divide Eras into smaller time periods. Epochs divide periods into smaller time periods.

The Fossil RecordThe Fossil Record

A fossil is any evidence of past life and can be: Footprints Plant or animal remains Molds and Casts

A fossil is any evidence of past life and can be: Footprints Plant or animal remains Molds and Casts

http://www.stonecompany.com/fossils/invertebrates/crustaceans/crabs/solnhofen/images/crabDSC03440z.jpg

Dunkleosteus (30 ft long; bony skull shown here is about 1 meter high)

Extinct at the end of the Devonian

Inferences from fossil evidenceInferences from fossil evidence

• Older fossils were simple in structure. As time passed life forms began to increase in size and complexity

• The types of animals found in a location can indicate the type of climate that animal was living in

• Coral fossils indicate a tropical climate, marine fossils indicate shallow or deep water environment

Look at ESRT and observe the bottom part of the column under life on Earth. Notice how animals begin as simple cellular animals

and eventually change to soft bodied animals, then shells

appear, then vertebrates, then reptiles and finally mammals. The process of change that produces

new life forms is called EVOLUTION.

Index FossilsIndex Fossils

Index fossils- Must have the following characteristics:

•Existed for a short period of time• Must be easily identifiable and abundant•Useful in marking a time

If an index fossil is found in a layer of rock, the layer must have been formed in specific period of time

Key BedKey Bed

•A single rock layer that has the same characteristics as an index fossil

•Relatively thin, widespread area, deposited rapidly, easy to identify

•A volcanic eruption can produce a key bed because an eruption happens over a short period of time and usually covers a large area