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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)

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Observation in the age of satellites

https://svs.gsfc.nasa.gov/vis/a000000/a003800/a003868/GlobalSnowNDVIFire.mp4

Earth Science in the age of computers

https://svs.gsfc.nasa.gov/vis/a010000/a011700/a011719/11719-1920-MASTER.mp4

What makes an idea scientific?

•  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’

www.savingadvice.com/images/blog/hello-kitty-bicycle.jpg

The Energy Cycle Source: http://www.noaanews.noaa.gov

The Sun

Sun’s energy output

•  3.8 x 1026 W total energy output

•  1.7 x 1017 W reaches Earth

•  Energy flux at Earth’s distance is 1370 W per m2

BP 3.4

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Energy flux on Earth’s surface

Earth Radius: R=6370 km

Energy flux: 1370 W/m2

Earth intercepts πR2=1.74x1017 W

Spread out over sphere, which has area 4πR2

Average energy flux is thus 1370 [W/m2]/4 = 342 W/m2

BP 3.5

Energy budgets •  Energy flow is measured in Watts per square meter •  1 W = 1 J/s •  First law of thermodynamics: conservation of energy

Source: http://stephenschneider.stanford.edu

The Energy Cycle

•  Drives all of the processes that we see operating on the Earth

•  Energy inputs –  Solar radiation: light, radiant heat,

etc., –  Geothermal energy: released

from nuclear breakdown of Uranium, Thorium etc.,

–  Tidal energy – a result of gravitational attraction of Moon

•  Energy losses –  Reflection into space –  Re-radiation, as radiant heat

Tides

Geothermal energy

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Solar energy

•  Energy comes from the sun as electromagnetic (or EM) radiation, mainly in the visible and infrared bands.

•  About 1.74 x 1017 W (Watts) or 174,000 TW (Terawatts)

Short wavelength Solar radiation 174,000 TW

Where does solar energy go? (1)

•  About 30% is reflected into space (52,000 TW) •  Just under half is converted to heat and is re-

radiated (81,000 TW)

Short wavelength Solar radiation 174,000 TW

Long wavelength radiation Reflected

into space 52,000 TW

Converted to heat 81,000 TW

Where does solar energy go? (2)

•  Just under a quarter goes into melting ice and evaporating water; energy is stored in the hydrosphere (40,000 TW)

•  350 TW are converted to winds, ocean currents, waves etc

Short wavelength Solar radiation 174,000 TW

Long wavelength radiation Reflected

into space 52,000 TW

Converted to heat 81,000 TW

Evaporation and melting 40,000 TW

Precipitation

Wind, Waves and currents

Water and ice storage bank

350 TW

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Where does solar energy go? (3)

•  40 TW are captured by living things

Short wavelength Solar radiation 174,000 TW

Long wavelength radiation Reflected

into space 52,000 TW

Converted to heat 81,000 TW

Evaporation and melting 40,000 TW

Precipitation

Wind, Waves and currents

Water and ice storage bank

350 TW

Photo-synthesis

40 TW Plant

storage bank

Decay

Buried organic matter

Geothermal energy

•  Energy is released within the Earth by the slow breakdown of Uranium, Thorium and other radioactive elements.

•  Total amount is estimated at ~32 TW

Short wavelength Solar radiation 174,000 TW

Long wavelength radiation Reflected

into space 52,000 TW

Converted to heat 81,000 TW

Evaporation and melting 40,000 TW

Precipitation

Wind, Waves and currents

Water and ice storage bank

350 TW

Photo-synthesis

40 TW Plant

storage bank

Decay

Buried organic matter

Geothermal energy 32 TW

Where does geothermal energy go?

•  This energy drives volcanoes, hot springs, earthquakes, and movements of continents.

•  It is also radiated in very small amounts, averaging ~60 mW/m2, from the Earth’s surface

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Where does geothermal energy go?

–  Volcanoes and hot springs on land 0.3 TW –  Volcanoes under the sea 11 TW –  Heat loss (conduction) from the surface 21 TW

Short wavelength Solar radiation 174,000 TW

Long wavelength radiation Reflected

into space 52,000 TW

Converted to heat 81,000 TW

Evaporation and melting 40,000 TW

Precipitation

Wind, Waves and currents

Water and ice storage bank

350 TW

Photo-synthesis

40 TW Plant

storage bank

Decay

Buried organic matter

Geothermal energy 32 TW

Volcanoes Hot springs 0.3 TW Heat flow 21 TW

Submarine volcanoes 11 TW

Where does tidal energy go?

•  Tidal energy: 27 TW

Short wavelength Solar radiation 174,000 TW

Long wavelength radiation Reflected

into space 52,000 TW

Converted to heat 81,000 TW

Evaporation and melting 40,000 TW

Precipitation

Wind, Waves and currents

Water and ice storage bank

350 TW

Photo-synthesis

40 TW Plant

storage bank

Decay

Buried organic matter

Geothermal energy 32 TW

Volcanoes Hot springs 0.3 TW Heat flow 21 TW

Submarine volcanoes 11 TW

Tides 27 TW

Summary of energy cycle

Short wavelength Solar radiation 174,000 TW

Long wavelength radiation Reflected

into space 52,000 TW

Converted to heat 81,000 TW

Evaporation and melting 40,000 TW

Precipitation

Wind, Waves and currents

Water and ice storage bank

350 TW

Photo-synthesis

40 TW Plant

storage bank

Decay

Buried organic matter

Geothermal energy 32 TW

Volcanoes Hot springs 0.3 TW Heat flow 21 TW

Submarine volcanoes 11 TW

Tides 27 TW

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Solar energy budget

Source: http://stephenschneider.stanford.edu

Laws of thermodynamics •  Energy is conserved (1st Law of Thermodynamics)

•  All energy flows are ultimately converted to heat. This reflects the 2nd Law of Thermodynamics:

–  Whenever energy is used to do mechanical work in a system, some of that energy is dispersed (lost) as heat.

–  Because heat is an unorganized, random vibration of molecules, we say that the entropy (a measure of disorganization) of the system has increased.

–  The net entropy of the universe always increases.

2nd Law of Thermodynamics •  Without some external source of energy, entropy on

Earth would increase until we use up all available energy (losing it as heat).

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2nd Law of Thermodynamics •  Without some external source of energy, entropy on

Earth would increase until we use up all available energy (losing it as heat).

Source: http://www.geocities.com/larkspur10/neo/228/towers.jpg

Source: http://www.noaanews.noaa.gov

The Sun

2nd Law of Thermodynamics

The Hydrologic Cycle •  Water cycle BP 1.9

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Hydrologic pathways: Evapotranspiration

•  Evaporation –  from

surface water

–  from land •  Transpiration

–  from plants

BP 1.9

Hydrologic pathways: Condensation and precipitation

•  Condensation –  Clouds

•  Precipitation –  Rain –  Snow

BP 1.9

Hydrologic pathways: Surface and subsurface flow

•  Melting •  Surface flow

–  Glaciers –  Streams –  Rivers

•  Infiltration •  Groundwater

movement

BP 1.9

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Hydrologic reservoirs

•  Oceans (97.5%)

•  Ice sheets (1.85%)

•  Groundwater (0.64%)

•  Lakes, rivers, atmosphere (.01%)

BP 1.9

Earth’s water budget

1015 = 1,000,000,000,000,000

Earth’s water budget

1015 = 1,000,000,000,000,000 (a “million billion”)

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Reservoir change

•  For most of these reservoirs, the rate of flow in approximately balances rate of flow out.

•  Volume of water in the reservoir is approximately constant

•  When flow in > flow out, reservoir expands •  When flow in < flow out, reservoir contracts •  The ice sheet reservoir has been getting smaller over

time because melting > snowfall

Residence time

•  Size of reservoir / flow rate = residence time •  A measure of the average time that a water molecule

spends in the reservoir •  Typical residence times:

Oceans and ice caps: thousands of years Streams and rivers: a few weeks Atmosphere: a few days

Hydrologic cycle BP 1.9

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The Rock Cycle •  Cycling of rock material at

surface of the Earth •  Three types of rock

Igneous Sedimentary Metamorphic

BP 1.12

Magma •  Melting point: 800-1200ºC

(depending on rock type) •  Molten rock is magma; at the

surface, it’s called lava

BP 7.5

Igneous rock

•  Cooling •  Solidification

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Intrusive Rocks

•  Magma cools below surface

•  Generally have larger crystals

•  “Phaneritic” (visibly crystalline)

Ansel Adams

Extrusive Rocks

•  Lava that cools above surface

•  Typically have microscopic crystals

•  “Aphanitic” (without visible crystals)

Source: USGS

Differences in Crystal Size

•  Intrusive rocks “phaneritic” large crystals

•  Extrusive rocks “aphanitic” small crystals

Due to differences in rate of cooling

Slow = large Fast = small

http://www.birdseyefoods.com

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Weathering Destructive processes that change the physical and chemical characteristics of rocks at the earth's surface.

Erosion Transportation of weathering products

Source: http://www.truecolorearth.com

Sediment Deposition à Sediment Source: http://en.wikipedia.org/wiki/McCormick's_Creek_State_Park

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Sedimentary rock Results from “lithification” of sediments Sedimentary Rock: Often “Clastic” (made up of fragments)

Source: http://library.thinkquest.org/05aug/00461/images/sandstone.jpg

Metamorphism •  Results from heat and pressure (without melting)

BP 4.22

Metamorphic rocks

•  New minerals •  Change in texture •  Fabric

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Igneous rock

•  For comparison…

Metamorphic rocks

•  New minerals •  Change in texture •  Fabric

The rock cycle: summary

Magma

Igneous rock

Weathering

Transportation

SedimentLithification

Sedimentary rock

Metamorphism

Metamorphic rockMelting

Erosion

Deposition

Cooling

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Other Cycles

•  Biogeochemical cycles

–  Nitrogen cycle –  Carbon cycle

(We’ll look at these later on.)