Earth’s History – 7th Grade Ms. De Los Rios 4.4 Essential Question: How do Scientist study Earth’s past? What is the Geologic Time Scale? How has Earth Changed Over Geologic Time? Geologic Time Pgs. 158-163

My Planet Diary pg. 158 Earth’s History In A Day Suppose you could squeeze all of Earth’s 4.6-billion-year history into one 24-hour day. The table shows the times at which some major events would take place. Write the letter for each event on the clock diagram. 2. Did anything surprise you About the data? If so, what? ________________________

What is the Geologic Time Scale? Pg. 159 r. 159 3rd The history of the Earth covers an enormous length of time. Scientists have developed new terms to identify long periods. Because the time 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 the geologic events and the evolution of life forms as shown in the fossil record.

1st Precambrian Time- The earliest part of the geologic time scale. Geologic Time Scale pg. 161 In the geologic time scale, scientists have placed Earth’s rocks in order by relative age (when rocks were formed) Then, they divided geologic time into parts, based on times in Earth’s history when there were major changes in life forms. 1st Precambrian Time- The earliest part of the geologic time scale. Covers 88% of Earth’s history The longest of the geologic time scale, ended 542 million years ago. Few fossils survived from this period.

Dividing Geologic Time pg. 161 Scientists divided the time between Precambrian Time and the present into three long units of time called eras. 3 Eras are: Paleozoic Era Mesozoic Era Cenozoic Era.

Dividing Geologic Time pg. 161 Moreover, scientists subdivided eras into units of geologic time called periods. The Paleozoic Era is made up of 6 periods

Dividing Geologic Time pg. 161 the Mesozoic Era is made up of 3 periods The Cenozoic Era is made up 3 periods. The last of these, the Quaternary Period, continues to the present time.

Assess Your Understanding Pg. 161 1a. Define The geologic time scale is a record of __________ and __________. b. Sequence-Number the following periods in order from earliest to latest. Neogene ________ Jurassic ________ Quaternary ________ Triassic _________ Cretaceous _________ c. Draw Conclusions-Refer to My Planet Diary and Figure 2. During which period did modern humans arise? ______________________________________________________

How Has Earth Changed Over Geologic Time? Pg. 162 Scientists use the principle of uniformitarianism to help explain Earth’s past. This principle explains that geologic processes that operate today are the same ones that operated in the past. Natural processes such as weathering, erosion, and plate tectonics have reshaped Earth’s surface. The distribution of land and water on Earth’s surface has changed over time. How can scientist infer about events in Earth’s history? Using fossils, evidence from rock layers, and radioactive dating,

Geologic Time – pg. 162-163 The Evolving Earth The timeline shows how Earth has changed over time. Identify each development with the period in which it occurred.

Assess Your Understanding pg. 163 1a. Explain How does uniformitarianism help scientists who are Studying Earth’s past? ____________________________________________________________________________________________________________ b. How do scientists study Earth’s past? Use an example from this chapter in your answer. I get it! I know that the ways Earth has changed over geologic time include____________________________________________ ______________________________________________________