Historical Geology studies the origin of
Earth and the development of the
planet through its 4.6- billion-year history.
Paleontology - the study of fossils
(living organisms, animals and plants
that once existed on the plant).
Geologic time• Thinking in terms of “millions of years”
• Try it in seconds, just for fun: 1,000,000 seconds
How many minutes is this? 1,000,000 seconds / 60 seconds per minute This = 16,667 minutes
How many hours is this? 16,667 / 60 minutes per hour = 278 hours
How many days? 278 hours / 24 hours per day = 11.6 days
• So, 1 million seconds ~ 12 days
How does 1 million compare to 1 billion?
• Again, in seconds just for fun: 1,000,000,000 seconds
How many minutes is this? 1,000,000,000 seconds / 60 seconds per minute This = 16,666,667 minutes
How many hours is this? 16,666,667 / 60 minutes per hour = 277,778
hours How many days?
277,778 hours / 24 hours per day = 11,574 days
Keep going…
• 11,574 days--how many weeks is this?
• 11,574 / 7 days per week = 1,653 weeks Great, now how many years is this?
• 1,653 weeks / 52 weeks per year
• This equals 32 years
• So, one billion seconds = 32 years
• And one million seconds = 11 days
• Now instead of seconds, lets think in YEARS
Understanding the evolution of Earth
requires an appreciation of the immensity of
geologic time
Geologic time
To understand geologic time, do not think in terms
of seconds, minutes, hours days and years (human perspective)
Geologic time
Example:
Himalayas start to develop 50 mya. It is difficult to say that Himalayas formed 50,000,000 years ago or
18,250,000,000 days ago.
Geologic time
EonLongest time unit
measured in billions of year. The Archean,
Proterozoic, and Phanerozoic are eons.
EraMeasured in hundreds of millions to billions.
Defined by the differences in Life-
forms found in rocks.
Period Defined by the life-
forms that were abundant or became
extinct during the time in which specific rocks
were deposited
Regardless of how a geologic time division was defined, each unit
contains specific characteristics that set it
apart from the rest of geologic history.
Hypotheses for Earth Development: Catastrophism
• 1600-1700s
• Landscape formed through a series of catastrophes Mountains, canyons formed during sudden
world-wide disasters triggered by unknowable causes that no longer operate