1. Outcomes: By the end of this Module you should be able to: Describe hot the solar system has evolved from a ball of gases released from a supernova explosion Describe the early Earth and its evolution Outline how living cells originated at a time when the atmosphere and environments were different from those presently found on Earth Explain how the evolution of photosynthesis shifted the balance of gases in the atmosphere Explain how the evidence provided by geological records suggests there have been climactic variations over Earth’s history

2. We all know what change means. Your body changes, seasons change, society itself changes. The Earth and its environments also change. This module focuses on the major changes that the Earth has undergone.

3.  Introduction: Geologic time  Part 1: The evolution of our solar system  Part 2: The evolution of Earth  Part 3: The evolution of life on Earth  Part 4: The evolution of the atmosphere  Part 5: Carbon in the atmosphere and hydrosphere  Part 6: Climatic variations

4. When studying the history of Earth, we must understand the concept of geologic time. Geologic time is the period of time over which the Earth’s rocks have formed. This first lesson we are going to learn about our current belief that Earth is 4.6 billion years old.

5.  In 1654, James Ussher calculated that the Earth was created 4004BC. He chose this date by adding all the generations described in the Bible back to Adam and then multiplied this by his estimated average generation.  Many scientists thought Ussher was wrong, it was to short a time span.

6.  In 1778 a Mathematician named Georges de Buffon estimated the Earths age based on experimental observation. He thought the Earth’s core was like iron and therefore heated iron canon balls and studied the rate at which they cooled.  He concluded the Earth was 75000 years. Still way off

7.  In 1830, geologist Sir Charles Lyell determined the 240 million years had passed since the beginning of the Cambrian period. He compared the degree of evolution shown in fossilised marine molluscs over time.

8.  In 1855 physicist William Kelvin, using Buffon’s principle of heat loss, thought the Earth was 20-30 million years old. Other scientists did not challenge this idea because there was no evidence to prove him wrong.

9.  In 1898 chemist John Joly determined the total amount of salt in the oceans is added by erosion from land. He thought that 100 million years had gone by to produce the current salt levels in the ocean

10.  In 1899 geologist Thomas Chamberlin challenged Kelvin. He thought another source of energy other than heat left over must exist. Other scientists working on the phenomenon of radiation proved him correct!

11.  In 1896 Henri Becquerel discovered that certain naturally occurring minerals emit radiation. And in 1904 New Zealand born Ernest Rutherford had a hypothesis of how radioactive decay occurred.

12.  In 1905 Bertram Boltwood and J.W.S Rayleigh developed a relatively simple radio- active dating technique to determine the age of certain minerals. Their initial results showed the Earth to be as old at 2000 million years.

13.  By 1960 the Earth’s age was increased to 3500 million years old.  Presently the oldest piece of crust ever sampled is from Mt Narryer in Western Australia dating between 4100 and 4200 million years.

14.  Because Earth’s crust is continually recycled and destroyed, it’s doubtful that scientists would find rocks that have not been altered since Earth’s formation. However meteorites that have fallen to Earth, that are believed to have formed at the same time as Earth and the solar system, have been dated back to between 4600 and 5000 million years.

15.  A geological time scale has been created which is divided into smaller periods and subgroups mainly based on fossil evidence.

16.  Read Pages 1-5 Prelim Spotlight Text  Start Electronic Vocab List Eg: Planet Earth and Its Environment 1. Geologic Time: The vast period of time over which the Earth’s rocks have formed.