15-09-04 1 Introduction to Earth Science: Studying the Earth • Scientific methods • Earth scientists: areas of study within the Earth sciences • Systems and cycles in Earth science • Applications of Earth and Atmospheric Science Read: Blue Planet: Ch. 1 The Earth System Scientific methods and the study of the Earth Source: USGS Experiment and observation • Physics and chemistry are primarily experimental sciences • Earth Science is primarily an observational science (though experiments are also used)
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15-09-04
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Introduction to Earth Science: Studying the Earth • Scientific methods • Earth scientists:
areas of study within the Earth sciences
• Systems and cycles in Earth science
• Applications of Earth and Atmospheric Science
Read: Blue Planet: Ch. 1 The Earth System
Scientific methods and the study of the Earth
Source: USGS
Experiment and observation
• Physics and chemistry are primarily experimental sciences
• Earth Science is
primarily an observational science (though experiments are also used)
• It can be tested against observation or experiment
BP 12.18
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What makes an idea scientific?
• It can be tested against observation or experiment
BP 12.18
The Scientific Method
A long, careful series of experiments or observations that aims to explain or understand the natural world.
Observation and hypotheses
Step 1: Observation
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The Scientific Method
Step 2: Hypothesis formation
hypothesis:
A tentative explanation for an observation, phenomenon, or scientific problem that can be tested by further investigation.
Step 3: Hypothesis testing
The Scientific Method
The Scientific Method
Step 3: Hypothesis testing
And steps 4, 5, 6, etc.
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The Scientific Method
Step 3: Hypothesis testing
And steps 4, 5, 6, etc.
If a hypothesis passes the tests…
Source: www.destination360.com
The Scientific Method
Hypothesis becomes theory
theory:
A set of statements or principles devised to explain a group of facts or phenomena, especially one that has been repeatedly tested or is widely accepted and can be used to make predictions about natural phenomena.
The Scientific Method • If, over many years
and much additional testing, the theory holds…
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The Scientific Method
Theory becomes law
law:
A statement describing a relationship observed to be invariable between or among phenomena for all cases in which the specified conditions are met
• Example: “Law of Conservation of Energy” (1st Law of Thermodynamics)
In a system of constant mass, the energy involved in physical or chemical change is neither created not destroyed but merely converted from one form to another
The Scientific Method
• Example: “Law of Conservation of Energy” (1st Law of Thermodynamics)
In a system of constant mass, the energy involved in physical or chemical change is neither created not destroyed but merely converted from one form to another
The Scientific Method
E = mc2
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The Scientific Method
Repeated testing, evaluation, modification of hypothesis, more testing…
Very powerful methodology!
• An example: principle of superposition
Sandstone layers in Nova Scotia
Principles: generalizations with exceptions
Principles: generalizations with exceptions • An exception:
overturned strata in mountain belts
Folded sedimentary layers in the Swiss Alps
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The principle of uniformitarianism
• Ancient sand dune, Zion, Utah
The principle of uniformitarianism
• Ancient sand dune, Zion, Utah
• Modern sand dune, Yuma, Arizona
The principle of uniformitarianism
• Ancient sand dune, Zion, Utah
• Modern sand dune, Yuma, Arizona
Are the processes that created ancient features similar to those that create modern ones?
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The principle of uniformitarianism
• Proposed by James Hutton in 1795 – Theory of the Earth
• Ancient features of the Earth are best interpreted in terms of processes that operate at the present day
• ‘The present is the key to the past’
Siccar Point, Berkwickshire, Scotland
‘Hutton’s unconformity’
• Hutton interpreted the contact between the lower rocks and the upper rocks as an ancient erosion surface, produced by processes similar to those operating at the present day
BP 1.12
Changes in Earth History
• Hutton proposed a very strict principle of uniformitarianism
• We now recognize that there have been big changes in Earth processes including:
long term changes (e.g. tectonics; evolution of the atmosphere)
short term changes (catastrophic meteorite impacts)
Source: exploratorium.com
Meteor Crater, Arizona
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Principle of actualism
• A more moderate version of Hutton’s principle is called actualism
‘The natural (i.e., physical and chemical) laws that allowed the formation of ancient features of the Earth are the same ones in operation today.’
• This allows for change!
Relationship to other sciences:
Source: USGS
• Earth science is largely an observational science
Relationship to other sciences: • Earth science makes use of principles and laws derived
from other sciences, such as physics, chemistry and biology. – Example: “Law of Conservation of Energy”
(e.g., 1st Law of Thermodynamics)
In a system of constant mass, the energy involved in physical or chemical change is neither created not destroyed but merely converted from one form to another
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Earth scientists: areas of study within the Earth sciences
Source: NASA
Geologists
• Field observations • Geologic maps • Samples • Chemical analyses • Resource
development and extraction
Shiprock Peak, New Mexico
Source: University of Wisconsin-Madison
Geophysicists
• Use variations in the Earth’s physical properties to determine subsurface structure, composition, etc.
Seismic velocities
Magnetic, electrical properties
Variations in strength of local gravitational field
• Examine the earth using natural phenomena such as earthquakes
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Paleontologists and Biogeographers
• Paleontologists Fossils and the history of life
• Biogeographers Distribution of living things at the present day
Hydrologists & Oceanographers
• Liquid water on and below the Earth’s surface
• Living things in
water • Sediments
deposited on the sea floor or the bottom of lakes
Atmospheric Scientists
• Meteorologists & climatologists
• Physics of the atmosphere
• Short term changes in the atmosphere (weather)
• Geographical variation and long term changes in the atmosphere (climate)
Source: University of Washington
Hurricane Katrina
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Glaciologists
• Behaviour and distribution of ice
• The impact of glaciers
on the landscape (e.g., erosion, deposition) and downstream environments
• Interactions between
ice masses and climate
Canine Glacio-hydrologists
Donjek
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Logan
Logan
Systems and cycles
A system is a portion of the universe that can be separated from the rest for the purpose of observing changes
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Types of systems
• Systems may be:
– Isolated – Closed – Open
BP 1.3
Isolated systems
• No matter or energy lost or gained
• Imaginary concept
BP 1.2
Closed systems
• No matter lost or gained; energy may be exchanged with surroundings
• The Earth is approximately a closed system
BP 1.2
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Open systems
• Matter and energy exchanged with surroundings
• Examples of open systems: – An ocean – An island – A forest – A leaf – You
BP 1.2
The Earth as a system
• Earth is approximately a closed system
• Note: – Small amounts of
gas are lost to space
– Small amounts of material are added by meteorites and comets
– These amounts are extremely small compared with the mass of the Earth
BP 1.5
Systems within the Earth
• The Earth system contains several major open systems – Atmosphere – Geosphere – Hydrosphere – Biosphere – Cryosphere
BP 1.5
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Cycles
• Cycles trace the flow of material or energy through systems
• Examples include: – The energy cycle – The hydrologic cycle – The rock cycle
• When a cycle is quantified it is sometimes called a ‘budget’