Transcript Principles of Earth History

VISUALIZING EARTH HISTORY
By Loren E. Babcock
Chapter 1
Introduction to Earth System History
What is Earth History?
Distinguish Earth history from Earth dynamics.
Geology is the science of the Earth.
Geology studies the composition, structure, origin, life forms,
physical and chemical processes affecting it, and its history.
The science of geology is divided into two broad but overlapping
subdisciplines referred to as:
Earth dynamics (or physical geology) and
Earth history (or historical geology).
What is Earth History?
Explain the meaning of a scientific theory.
Geology is based on facts or observations about nature.
The Scientific Method – is a scientific investigation involving
an iterative process of empirical observation,
hypothesis building (with a predictive or
retrodictive component), and testing.
What is Earth History?
Explain the meaning of a scientific theory.
A scientific theory is a unifying idea that incorporates a
number of provisionally accepted hypotheses.
The popular meaning of “theory” is speculative,
an idea in need of testing, and one that is
not necessarily widely accepted by scientists.
Scientific theory is a scientific concept that is tantamount to fact.
What is Earth History?
The theories of plate tectonics and biological evolution.
Two important scientific theories are central to an
understanding of Earth history:
plate tectonics and biological evolution.
The Early Earth and Plate Tectonics
http://www.youtube.com/watch?v=QDqskltCixA
What is Earth History?
The theories of plate tectonics and biological evolution.
Plate tectonics theory is the great unifying idea of geology.
It states that the Earth’s outer shell (the lithosphere), which
consists of the crust and upper mantle, is cracked and
composed of pieces that float on a hot, deformable
asthenosphere.
The pieces move in various directions, and may slowly
spread apart, collide, or slip past one another.
What is Earth History?
The theories of plate tectonics and biological evolution.
Evolutionary theory is the great unifying idea of biology.
It is the process by which biological species give rise to
other species by way of genetic changes.
What is Earth History?
The theories of plate tectonics and biological evolution.
Plate tectonics and evolutionary theories provide a sound,
consistent framework within which to interpret the past
and present, and both ideas are well tested and supported
by an overwhelming amount of evidence.
What is Earth History?
Composition of the Earth’s Crust
Crust - The outermost layer of the Earth, defined by
density, composition (Si, O), and a seismic velocity difference
from the underlying mantle. Oceanic: 5-10km, continental: 33km.
Mantle – It’s composed of Si, O, Mg and Fe.
It extends to 2900km depth.
Lithosphere - Outer, relatively rigid layer of the Earth,
approximately 100 km thick, overlying the asthenosphere.
It includes the entire crust plus the upper mantle.
Asthenosphere - Layer within the upper mantle and
below the lithosphere where rocks are relatively
ductile and easily deformed.
Overview of Earth Systems
Explain what parts of the Earth system geologists study.
The systems approach to studying the Earth is a way of
breaking down large, complex problems into smaller
components while remaining mindful of the
connections between the components.
Earth system - The sum of the physical, chemical, and
biological processes operating on and within the Earth.
Overview of Earth Systems
Explain what parts of the Earth system geologists study.
A change in one component in a system commonly has
effects in other components and its systems.
The usage of oil increases carbon dioxide, water vapor,
and other gaseous chemicals to the atmosphere;
these gases limit heat loss from the Earth’s thin
atmosphere and promote an increase in temperature.
Overview of Earth Systems
Explain what parts of the Earth system geologists study.
Overview of Earth Systems
Identify the major geologic processes operating on Earth.
Earth is a planet that differs markedly from
others in the Solar System.
Three important processes have substantially modified
the Earth’s surface over time:
1, tectonics,
2, the action of water in various forms
3, biological processes,
Overview of Earth Systems
Identify the major geologic processes operating on Earth.
1, tectonics, which involves the movement of lithospheric
plates across the planet’s surface, and which is responsible
for the recycling of rocks;
2, the action of water in various forms (liquid, ice, and water
vapor), which plays a major role in weathering and erosion,
and in the formation of rocks; and
3, biological processes, living organisms are source of profound
change on Earth surface, and their effects alter surface and
subsurface areas, water systems, and the atmosphere.
Overview of Earth Systems
The roles of water, carbon, and oxygen in Earth systems.
Key elements of the Earth system are the cycles of essential
ingredients for life and some of the forces of change:
water, carbon, oxygen, and other chemicals.
Overview of Earth Systems
The roles of water, carbon, and oxygen in Earth systems.
The water cycle is used
to describe the endless
exchange of water
among the atmosphere,
oceans, lakes, streams,
through living
organisms, and through
the ground.
Overview of Earth Systems
The roles of water, carbon, and oxygen in Earth systems.
Water, carbon, oxygen, and other nutrients are cycled
through atmospheric, biological, and geological systems.
Carbon and oxygen from the atmosphere may be used by
living organisms.
Oxygen is used for respiration by animals, and carbon dioxide is
used by plants and some bacteria for photosynthesis.
Overview of Earth Systems
The roles of water, carbon, and oxygen in Earth systems.
Sediments or derivative rocks may be exposed
to weathering and erosion, and the elements
may be released to continue cycling through
the Earth systems.
Earth is not entirely a closed set of systems.
Biological processes depend heavily on both the
presence of liquid water from Earth, and a constant
stream of radiation from the Sun.
Principles of Earth History
Seven important principles guide our interpretation of
Earth history, and provide a way of deciphering historical
events in their correct relative time sequence:
uniformitarianism,
superposition,
original horizontality,
lateral continuity,
cross-cutting relationships,
included fragments,
and biotic succession.
Principles of Earth History
Explain Hutton’s principle of uniformitarianism.
Uniformitarianism - The principle that processes acting upon
the Earth today have also operated in the geologic past.
The concept of uniformitarianism, which is often
expressed in the phrase “the present is the key to the past.”
Principles of Earth History
Describe Steno’s three principles of stratigraphy.
Stratigraphy, the science of layered rocks, developed
from three principles first stated by Niels Stenson (1638-1687),
who latinized his name to Nicolaus Steno.
Steno was the first to formally recognize the importance
of stratification, or horizontal layering.
Stratification of sediments occurs as the result
of differences in particle size and density.
Principles of Earth History
Describe Steno’s three principles of stratigraphy.
The principle of Original Horizontality
Steno’s principle of original horizontality states that sedimentary
layers were deposited nearly horizontally and parallel to the
Earth’s surface.
Principles of Earth History
Describe Steno’s three principles of stratigraphy.
The principle of Lateral Continuity
Steno’s principle of original lateral continuity states that at the
time of deposition, strata extended continuously in all
directions until they terminated by thinning at the edge of a
basin, ended abruptly at a barrier to sedimentation, or graded
laterally into a different sediment type.
Principles of Earth History
Explain Lyell’s two principles of stratigraphy.
Lyell provided interesting illustrations of the concept of
uniformitarianism, and provided cogent explanations for
geological phenomena that countered the prevailing
geological philosophy of the time—catastrophism.
Catastrophism (rooted in biblical scriptures) was a paradigm
that attempted to explain the development of erosional
surfaces and the extinction of species by violent, rapid,
calamities, like giant floods.
Principles of Earth History
Explain Lyell’s two principles of stratigraphy.
Lyell also introduced two other general principles of geology:
Principle of cross-cutting relationships – States that
a rock unit, sediment body, or fault that cuts another
geologic unit is younger than the unit that was cut.
Principle of included fragments - States that
fragments of rock within a larger rock unit
are older than the rock in which they
are enclosed.
Principles of Earth History
Understand Smith’s principle of biotic succession.
Principle of biotic succession - The principle that body
fossils occur in strata in a definite, determinable order.
This final major principle used to interpret the
relative ages of strata was proposed by the
English engineer and surveyor, William
(“Strata”) Smith (1769–1839).
Principles of Earth History
Understand Smith’s principle of biotic succession.