Geological Time Scale AIM How have stratigraphy and radiometric dating been used to construct the geological time scale The History of Earth Earths history has been studied through 2 methods ID: 656987
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Slide1
Unit 1- Earth Systems and Resources
Geological Time ScaleSlide2
AIM:
How have stratigraphy and radiometric dating been used to construct the geological time scale?Slide3
The History of Earth
Earth’s history has been studied through 2 methods:
Examining sequences of rock layers
Radioactive dating Slide4
Stratigraphy
Stratigraphy- branch of geology that studies
rock layers (strata)Slide5
Rules of Stratification
Rock layers (
strata
) are laid down in
succession
with each strata representing a “slice” of time
The principle of superposition- younger layers are on
top
, older layers are on
bottomSlide6Slide7
Geology
The
fossil record
of life on earth is captured in the rock layers of earth
The fossil record is our greatest source of information about the
evolution
of life on earthSlide8Slide9Slide10
The History of Earth
Using fossil evidence and the concepts of
stratification
, Earth’s history has been organized into various units according to
major events
that took place in each period.
This is called the
Geologic Time ScaleSlide11Slide12
Earth’s history has been divided into 4 major
Eras
, which are furthers categorized into
Periods.Slide13
Earth’s Eras
Cenozoic
Era
Mesozoic
Era
Paleozoic
Era
Precambrian
EraSlide14Slide15Slide16
TODAY
Today, we are in the
Cenozoic
Era, in the
Quaternary
Period
Cenozoic Era
(
65
mya
)- begins after extinction of
dinosaurs
; characterized by the evolution and diversification of mammalsQuaternary Period (1.8 mya) - Ice ages, evolution of humanSlide17
The History of Earth
Scientists estimate that Earth is
4.5 billion
years old
Radiometric Dating- decay of
radioactive elements
in rocks are quantified to determine age in yearsSlide18
Relative Age- rules of
stratification
to identify a chronological series of evolutionary and geological events
Fossil
evidence
Strata are laid down in succession
For any given strata, the rock layer above is younger, the rock layer below is older.Slide19
Absolute Age
- radioactive decay of elements in rock to determine age in years
“
radiometric
dating”Slide20
The Structure of EarthSlide21
Crust
U
ppermos
t
layer of earth
Continental
Crust- 20-30
miles deep
Oceanic Crust- 7
miles deep
Rocky and brittle, and can
fracture
in earth quakesSlide22Slide23
Mantle
Composed
of iron, magnesium, aluminum, and silicates
Mostly solid, but the uppermost portion is more “
plastic-like
”Slide24
Core
Center
of the earth
Mosly
iron
Outer core = solid
Inner core = liquidSlide25
HOMEWORK
15 Questions