Download Geologic Time Geologic Time

Geologic Time
How old is the Earth?
Archbishop Ussher (mid 1600’s), a respected scholar of the Bible
estimated the age of the Earth to be about 6000 years old (born in
4004 BC)? Estimates were derived by reconstructing family lines
through the Scriptures. Ussher’s work gained widespread
acceptance among scientific and religious leaders of his day.
During the 17th and 18th centuries the doctrine of catastrophism
strongly influenced people’s thinking about the Earth.
James Hutton (late 1700’s) put forth a fundamental principle that is
a pillar of Geology today – uniformitarianism or the present is the
key to the past. He further suggested that the Earth must be much
older than almost 6000 years.
Hadrian’s wall – built in 100 AD.
Geologic Time
How old is the Earth?
Absolute versus relative dating
Relative dating:
principle of superposition
youngest
oldest
assuming the rocks have not been overturned…
principle of uniformitariansim – the present is the key to the past
law of faunal succession
1
Geologic Time
How old is the Earth?
Absolute versus relative dating
Absolute dating:
Ages determined through radiometric dating techniques.
Is only applicable with materials that are radioactive.
Radioactivity involves the spontaneous decay/breakdown of a
parent element into a daughter element. This rate of decay is
uniform and constant and not affected by pressure, temperature or
chemical composition.
Geologic Time
Radiometric dating – radioactive decay
2
Geologic Time
So what does absolute dating tell us about the Earth’s age?
It is a very, very old place
4,600,000,000 years old
Geologic Time
Geologic spiral
3
Geologic Time
Early life began
developing during this
era. No land plants or
animals.
Precambrian era represents about
88% of all geologic time (4,600
million years (my) to 570 my).
Geologic Time
Paleozoic era represents
about 8% of all time (570
my to 245 my).
Life bursts onto the land masses.
4
Geologic Time
Mesozoic era represents
about 3% of all time (245
my to 66 my).
Reptiles flourish and mammals begin.
Geologic Time
Cenozoic era represents
about 1.5% of all time (66
my to present).
Most of what we see today developed during this era.
5
Geologic Time
Geologic time can be divided into four unequal periods of time called
era’s:
Precambrian era represents about 88% of all geologic time (4,600
million years (my) to 570 my). Early life began developing during
this era. No land plants or animals.
Paleozoic era represents about 8% of all time (570 my to 245 my).
Life bursts onto the land masses.
Mesozoic era represents about 3% of all time (245 my to 66 my).
Reptiles flourish and mammals begin.
Cenozoic era represents about 1.5% of all time (66 my to present).
Most of what we see today developed during this era.
Geologic Time
4,600,000,000 years old
4.6 billion years (by) = 6 days,
Each day is ~750 my, each second is 8,700 years, this 50 minute
class would last 26,000,000 years
Monday - noon Tuesday the Earth cooled, generated a primitive
atmosphere and produced water. Life began at noon on Tuesday
and unfolded over the next four days.
4:00 pm on Saturday, the big reptiles came on, by 9:00 pm they
were gone.
At 11:57 pm, man appeared and the industrial revolution last 1/40
of a second.
6
Geologic Time
4,600,000,000 years old
Geologic Time
4,600,000,000 years old
Law of faunal succession – states that older rocks contain more
primitive fossils (things that used to be alive) than younger rocks
which contain more complex fossils.
Evolution – descent with modification. All things change over time.
Mechanisms:
mutation
natural selection
Since fitter organisms produce more offspring, over time the nature
of a population changes
7
Geologic Time
4,600,000,000 years old
Direct human observation such as:
•
breeding for improved crops and domesticated animals
•
changing of moth pigmentation in Great Britain,
•
variation in Galapagos Island finches as a result of climate and food
resources change
•
the development of antibiotic resistance by numerous strains of
bacteria.
Geologic Time
4,600,000,000 years old
DNA studies – the blue print for all living things. How they are made.
•
99% similarity between human and chimpanzee DNA strands . This
DOES NOT suggest that we came from apes or vis-versa. It simply
indicates that we share a common ancestor.
8
Geologic Time
Evolution evidence
Faunal succession – the fossil
record shows evidence of
change over time.
Paleontologists have revealed
numerous elegant examples of
sequences of faunal succession
such as
•
the evolution of whales from
terrestrial mammals,
•
the evolution of birds from small
running dinosaurs, and
•
a three fold increase in brain
size during the last 4 million
years of human evolution.
Geologic Time
Evolution evidence
Homology - similarity of structure
- anatomical similarity
Vestigial properties - remnant
features no longer functional
such as:
•
the vestiges of tiny leg
bones embedded in the skin
of certain whales, or
•
the non-functional nubs of
pelvic bones in some
snakes, surviving as
vestiges of ancestors with
legs.
9