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Explore the origin and evolution of Earth through its 4.6-billion-year history, from the formation of the Himalayas to the study of fossils in paleontology. Delve into geologic time divisions like Eons, Eras, Periods, and Epochs, understanding key aspects such as Catastrophism and Uniformitarianism.
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Historical Geology studies the origin of Earth and the development of the planet through its 4.6- billion-year history.
Historical geology investigates the sequence of events that have occurred in the past.
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
Geologic time Understanding the evolution of Earth requires an appreciation of the immensity of geologic time
Geologic time Time is the main aspect of Geology
Geologic time To understand geologic time, do not think in terms of seconds, minutes, hours days and years (human perspective)
Geologic time To understand geologic time you must think in millions of years.
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 • The time divisions are: Eon Era Period and Epoch
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.
PeriodMeasured in terms of tens of millions to hundreds of millions of years.
Period Defined by the life-forms that were abundant or became extinct during the time in which specific rocks were deposited
EpochMeasured in millions to tens of millions of years. Defined by different groups of organisms.
Regardless of how a geologic time division was defined, each unit contains specific characteristics that set it apart from the rest of geologic history.
Geologic Time “The Present is the Key to the Past”
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
Uniformitarianism - the processes occurring today have been occurring since Earth formed.
Uniformitarianism means: • Geological processes operate over extremely long periods of time • Catastrophic events are included as punctuated events • Rates and intensities vary but physical and chemical laws have remained the same • Example: erosion
