Download Earth`s History… Earth s History…

Earth’ss History…
Earth
History…
• The
The earth has a history much like human earth has a history much like human
civilization has a history.
– Major events
Major events
– Distinctions of time
– Periods of lost time
Periods of lost time
– Distinct cultures
• Rather than on paper the Earth’s history is written in the rocks.
Uniformitarianism…..
• The present is the key to the past…
• The events of today have always taken place.
2.9 Billion Years Ago
Today
Geologic Timescale…
• Human History is compiled in books – Earth’s history is compiled in the rocks….
• Geologic Timescale.. Earth’s Age ‐Apx. 4.6 billion years
– Events are placed in chronological order and grouped into Eons Eras Periods Epochs
Eons, Eras, Periods, Epochs …
– Each grouping is marked by distinct major events and ages in m.y.a (millions of years ago) are given….
– The timescale is a living document. Meaning the groupings, events and times are based on our most current knowledge and are constantly changing
knowledge and are constantly changing……
• Geologic Timescale –
g
A summary of the major events in y
j
Earth’s history is based on living things (fossil evidence).
How do scientist divide geologic time ?????
time ?????
• Fossil Record …….
Fossil Record …….
4 Major Time Scale Divisions….
4 Major Time Scale Divisions….
• Eons – largest segments of time…
• Eras – based on changes in life forms (based on mass extinction events)
• Periods – existing life world wide.
• Epochs ‐ Differences in life forms continent to continent.
i
Precambrian Time.. (4 5 bya 500 mya)
(4.5 bya. –
500 mya)
* Longest part of Earth’s history (apx. 4billion years).
• Life (little to none) – simple, single‐celled organism. organism
• ex) bacteria, algae, fungus.
Paleozoic Era…
( 500
( 500mya –
250
250 mya.)
)
• Means Ancient Life : Age of Marine g
Invertebrates.
• Life Life – Marine (fish), amphibians(breath Marine (fish) amphibians(breath
oxygen ), first reptiles, first land plants.
• Geology ‐
Geology Pangaea formed, Many Volcanoes, Pangaea formed Many Volcanoes
Appalachian Mountains.
• End ‐mass extinction of land (70%) and d
fl d(
) d
marine animals (90%) . Sea level drop and climate change.
li
h
Mesozoic Era
(250 mya 65 mya.) (250 mya. –
65 mya )
• Means Middle Life: Age of Reptiles
Means Middle Life: Age of Reptiles
• Life ‐
if First flowers and birds. Dinosaurs i fl
d bi d
i
evolved and dominated.
• Geology – Pangaea breaks up. • End – Dinosaur mass extinction (asteroid impact).
Cenozoic Era
(65 mya. – today)
• Cenozoic Cenozoic ‐ Means Recent Life: Age of Means Recent Life: Age of
Mammals.
• Life –
Life Evolution of mammals. First humans Evolution of mammals First humans
(homo sapiens).
• Geology –
G l
A d Al Hi l
Andes; Alps; Himalayas. Cooler C l
climates (ice ages).
• End – Still going on ….
Difficulties with Compiling the Timescale
• There is not a complete record of events in any one place.
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• Much of the record is based on past life (
(fossil record). However, there are some cases )
,
where this record is incomplete.
• We need to rely on geologic “correlation” (matching) methods
(matching) methods….
Methods of Rock Correlation….
Methods of Rock Correlation….
• Relative age dating laws…..
Relative age dating laws
• Using fossil records…..
i f il
d
• Rock Correlation…
• Walking the outcrop (simplest & most direct).