Transcript Topic 1a-Introduction to Geological Time - Fellows

PLANET EARTH AND ITS ENVIRONMENT
A 5000-MILLION YEAR JOURNEY
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
PLANET EARTH AND ITS ENVIRONMENT
A 5000-MILLION YEAR JOURNEY
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.
TOPIC 1 OVERVIEW
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

GEOLOGIC TIME
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.
GEOLOGIC TIME


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.
GEOLOGIC TIME


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
GEOLOGIC TIME

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.
GEOLOGIC TIME

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.
GEOLOGIC TIME

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
GEOLOGIC TIME

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!
GEOLOGIC TIME

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.
GEOLOGIC TIME

In 1905 Bertram
Boltwood and J.W.S
Rayleigh developed a
relatively simple radioactive dating technique
to determine the age of
certain minerals. Their
initial results showed
the Earth to be as old at
2000 million years.
GEOLOGIC TIME


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.
GEOLOGIC TIME

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.
GEOLOGIC TIME

A geological time scale
has been created which
is divided into smaller
periods and subgroups
mainly based on fossil
evidence.
HOMEWORK
Read Pages 1-5 Prelim Spotlight Text
 Start Electronic Vocab List

Eg:
1.
Planet Earth and Its Environment
Geologic Time: The vast period of time over
which the Earth’s rocks have formed.