KEY CONCEPT The geologic time scale divides Earth

1
KEY CONCEPT The geologic time scale divides
Earths history based on major past events.

• Tollund Man
• Died about 2200 years ago in what is now Denmark.
  
• Details such as his skin and hair were preserved
  by the bog in which he was found.

A bog is a type of wetland that accumulates peat,
the deposits of dead plant material.
2
Index fossils are another tool to determine the
age of rock layers.

• Index fossils can provide the relative age of a
  rock layer.
• Defined as
• Fossils of organisms that existed only during
  specific spans of time over large geographic
  areas.
• Characteristics
• Common
• Easy to identify
• Found widely around the world
• Only existed for a relatively brief time

3
(No Transcript)
4
Index fossils are another tool to determine the
age of rock layers.

• Examples
• Index fossils include fusulinids and trilobites.
• Non-example
• Any fossil that is rare or only found in a
  certain region.

5
The geologic time scale organizes Earths
history.

• The history of Earth is represented in the
  geologic time scale.

• Geologic Time Scale
• Representation of the history of the Earth that
  is organized by major changes or events.
• Organized into Eons, Eras, Periods and Epochs.

6
The geologic time scale organizes Earths
history.

• Eons represent the greatest expanses of time.
  There are 4 Eons Hadean, Archean, Proterozoic,
  and Phanerozoic.
• The Hadean, Archean, and Proterozoic are
  collectively known as Precambrian Time, from 4.56
  billion years ago to 540 million years ago.
• Eons are divided into Eras.

7
The geologic time scale organizes Earths
history.

• Eras last from tens to hundreds of millions of
  years and consist of 2 or more Periods.
• Periods last for tens of millions of years and
  are the most commonly used units of time.
  Associated with rock systems.
• Epochs last for several millions of years and
  are the smallest units of time.

8

• Eras last tens to hundreds of millions of years.

• consist of two or more periods
• three eras Cenozoic, Mesozoic, Paleozoic

9
Eras last for tens to hundreds of millions of
years.

• Cenozoic Era Evolution of primates,
  diversification of mammals, flowering plants.
• Continues today.

10
Eras last for tens to hundreds of millions of
years.
2) Mesozoic Era Evolution and extinction of
dinosaurs, evolution of ferns and cycads and
mammals.
11
Eras last for tens to hundreds of millions of
years.
3) Paleozoic Era All existing animal phyla
developed, earliest land plants evolved.
Liverworts
Mosses