Transcript The Denudation Dilemma, Deep Time and the Science of Geology

Hutton’s Solution and “Deep Time”
“No vestige of a beginning…
No prospect of an end.”
The Age of Enlightenment
Late 18th century
Tremendous advances in science, politics,
philosophy, economics, etc.
Thomas Jefferson and Benjamin Franklin
American figures in the Enlightenment
James Hutton
A “gentleman farmer”
Associate of James Watt
and other members of
the “Oyster Club”
The Scottish
Enlightenment –
centered in Edinburgh
(Edinboro)
Hutton and Deism
Hutton was a Deist
Deism held that one could gain greater
understanding of God by understanding nature –
his creation
The “Denudation Dilemma - a theological
conundrum
Denudation Dilemma
Rock and soil are essential to life
Rock is the foundation for where we live
Soil is the foundation of agriculture – sustains life
To the Deists, this was evidence of God’s
beneficence
Denudation Dilemma
Rocks decay at Earth’s surface – weathering
Soil is washed away from farmlands – erosion
Weathering and erosion indicate destruction of
the land
Martin Luther predicted that the world would end
as a result of erosion
The Dilemma
How can one reconcile God’s beneficence with
the destruction of the land, which is essential for
life?
Hutton’s Observations
Processes of weathering and erosion are slow
Many rocks visible on the land are made up of
the products of weathering and erosion
These rocks are Sedimentary Rocks
Sediments accumulate in the ocean, so these
rocks originally formed in the ocean
The Riddle
How can rocks that formed below sea level be
found on land?
More of Hutton’s Observations
Not all rocks form by accumulation of sediment
Some rocks are made of crystals
These rocks show signs of having formed at very
high temperatures from molten material
These are Igneous Rocks
Arthur’s Seat and Salisbury Crags
Hutton’s Solution
Igneous rocks provide evidence for heat within
the Earth
Heat is capable of work (Watt’s influence)
Heat within the Earth lifts rocks from the sea and
creates new land
The dilemma is solved because as erosion
destroys land, heat uplifts new land
Concept of the Rock Cycle
Implications of Hutton’s Solution
Earth processes are slow
Great changes can be accomplished with great
amounts of time
Evidence of great expanses of time recorded by
the rocks
Conclusion: the Earth must be extremely old
Evidence for Deep Time –
Hutton’s Unconformity
An old Earth
Recycling of Earth materials
Evidence for earlier episodes of recycling
“No vestige of a beginning… no prospect of an
end.”
Hutton’s “Theory of the Earth” - 1785
Playfair’s Commentary
“The mind seemed to grow giddy looking so far
into the abyss of time…”
What’s so remarkable about Hutton’s Ideas?
Contrary to prevailing views of the time
Based on observation – what he saw
Hutton drew inferences from his observations
Inferences are hypotheses
Hypotheses are testable
This is an application of the scientific method to
study of the Earth
Science and the Scientific Method
Science – a way of knowing
Objective
Based on observation
Scientific Method – a rational way of verifying
what is “known”
Nothing is absolutely “true” in science. All ideas
are subject to rejection as they are tested
Science and the Scientific Method
Proposed explanations are hypotheses
Hypotheses are tested by
Experimentation
Prediction and verification
Further observation
Well-tested hypotheses may be elevated to the status of
theory
Well-tested theories may eventually become natural
laws or simply laws