Geologic Time - California State University, Sacramento time.pdf · Geologic Time Geologic time can...
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1 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 17 th and 18 th 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 principle of uniformitariansim – the present is the key to the past law of faunal succession assuming the rocks have not been overturned…
Transcript of Geologic Time - California State University, Sacramento time.pdf · Geologic Time Geologic time can...
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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 linesthrough 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 catastrophismstrongly 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
principle of uniformitariansim – the present is the key to the past
law of faunal succession
assuming the rocks have not been overturned…
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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 TimeRadiometric dating – radioactive decay
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Geologic TimeSo 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
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Geologic Time
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.
Geologic Time
Paleozoic era represents about 8% of all time (570 my to 245 my).
Life bursts onto the land masses.
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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.
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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,
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.
At 11:57 pm, man appeared and the industrial revolution last 1/40 of a second.
Each day is ~750 my, each second is 8,700 years, this 50 minute class would last 26,000,000 years
4:00 pm on Saturday, the big reptiles came on, by 9:00 pm they were gone.
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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
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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.
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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
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.
Evolution evidence
