LEQ:LEQ::: What is Geologic Time? What is Geologic Time? How How can a model help me visualize the can a model help me visualize the length and vastness of geologic length and vastness of geologic time? What is the Geologic Time time? What is the Geologic Time Scale? What are the units of the Scale? What are the units of the Geologic Time Scale?Geologic Time Scale?

• Key terms: geologic time, geologic time scale, eon, era, period, epoch.

Appreciating Geologic TimeAppreciating Geologic Time

• Getting a personal vision of geologic time is a concept that is critical in Earth Science.

• An easy way to get a vision of geologic time is when you begin to get a good concept of the vastness of geologic time.

• A model is very helpful.

Lets Start with Numbers Lets Start with Numbers (and the power of 10)(and the power of 10)

• On your notes page, print the following number:• One Thousand• 1,000• One Hundred Thousand• 100,000• One Million• 1,000,000• One Hundred Million• 100,000,000• One Billion• 1,000,000,000

Asterisks on the pageAsterisks on the page• Number of asterisks on the page:• 2000• Number of pages needed for 1 million asterisks• 500• Number of asterisks in a ream of paper:• 1,000,000• Number of asterisks in a case of paper:• 10,000,000

ModelingModeling• Lets use the asterisks to help us make a model.• Each asterisk is 1 year.• Number of years on one page:• 2000 years• Number of pages needed for 1 million years• 500 pages• Number of years in a ream of paper:• 1,000,000 years• Number of years in a case of paper:• 10,000,000 years.

Units of timeUnits of time• Work with a partner, and list the following

units of time from the largest to the smallest:

• Hour Day• Millennium Century• Year Week• Month Second• Minute Decade

Earth’s AgeEarth’s Age

• Earth’s age is estimated to be:

• 4.6 billion years old.

• 4,600,000,000

• Number of cases for 4,600,000,000:

• 460 cases• With each case having 5000 pages and each page

having 2000 years.

Geologic TimeGeologic Time

• Earth’s history has been 4.6 billion years in the making.

• This history is known as geologic time.

The Geologic Time ScaleThe Geologic Time Scale

• Because the span of Earth’s past is so great, geologists use the geologic time scale to show Earth’s history.

• The geologic time scale is a record of– Life forms in Earth’s History.– Geologic events in Earth’s History.

Units of Geologic TimeUnits of Geologic Time• In a similar way we divide time into units,

geologists divide Geologic time into units.

• Units of geologic time (largest to the smallest):– Eon – Era– Period– Epoch

• Each eon, era, period, and epoch is given a specific name.

What time is it? What time is it? (in Geologic Time)(in Geologic Time)

• We currently live in the:– Holocene Epoch of the:

– Quaternary Period of the:

– Cenozoic Era of the:

– Phanerozoic Eon