Introduction

We will consider all spheres of Earth

Lithosphere – Rock – GeologyAtmosphere – Air - Meteorology & ClimatologyHydrosphere – Water – OceanographyBiosphere – Life - Biology

Our goal is to understand interactions between spheres

http://www.hcsi.com/im_lib/space/geosna.jpg

First, we must agree on a method of work

Lava lamp

Scientific Method

• Hypothetico-deductive framework

• Hypotheses have testable consequences

• We test hypotheses to try to falsify them

• Karl Popper

1934 Popper Logic of Scientific Discovery

http://www.eeng.dcu.ie/~tkpw/

Falsification

• Paradigm shifts

Book: The_Structure_of_Scientific_Revolutions (1962)

biography of

An example: The earth’s orbit

• The Greek philosophers including Aristotle (384 BC - 322 BC ) observed the Sun rising in the east and setting in the west and inferred that the Sun revolved around Earth in a geocentric (Earth-centered) orbit.

http://en.wikipedia.org/wiki/Aristotle

Galileo's Letter to the Prince of Venice

http://www.mira.org/fts0/planets/099/text/txt002x.htm

Aristotle’s model is wrong

• Galileo’s observations of the orbits of Jupiter’s four largest satellites revealed that the Aristotle-Ptolemy model is unbelievable

• Objects that do not orbit the Earth

• We now know that the planets, including the Earth, orbit the Sun

http://www.hcsi.com/im_lib/imlib_space.html

IoEuropa

Callisto

Ganymede

http://www.enchantedlearning.com/subjects/astronomy/planets/jupiter/moons.shtml

A new lawA new law Isaac Newton (1665) discovered the force that

held the planets in their orbits around the sun - gravity.

gravitation, "every body in the universe attracts every other body.“

Force = mass x acceleration = maGravitational Force = gm1m2/r2 identify symbols

Both orbit, but …

Sun is much more massive, appears to hold still while the earth orbits around it.

We will see “g” again

How Far Away?

• We use the speed of light to indicate distance – light years 9460 billion kilometers

• Nearby Cepheids (variable stars) maximum brightness varies with period

• Measure apparent brightness and get distance

of far away Cepheids

• Our galaxy, the Milky Way, is 100,000 light years across (diameter)

Continuous, Emission and Absorption Spectra

White light contains a continuum of colors from short wave violet to long wave red

Hot, dense materials emit discrete "emission" spectra

When light with a continuous spectrum passes through a cold, rarefied gas, an absorption spectrum results.Each gas absorbs the same wavelengths that it emits when it is hot.

The spectrum of the light from our Sun is an Absorption spectrum.

Hydrogen

Helium

Redshift: absorption spectra shift to red with retreat of the emitter

Analogy: Passing train whistle, high to low frequency = short to long wavelength“Doppler Effect”

Very distant objects aren’t just single stars, those are galaxies of stars! Hubble: What if their colors reflect their speed and

direction?

Blue, moving toward us

Red, very distant, moving away fast

Hubble Space Telescope

The Hubble Redshift

• Hubble discovered that the most distant galaxies with Cepheids had their light

shifted to the red end of the spectrum. This meant that they are moving away from us.

• Hubble: Turn this into a new yardstick: the redder the shift, the further the galaxy

• Result: the edge of the universe (furthest objects we can detect) is approximately 15 billion light years away.

http://en.wikipedia.org/wiki/Edwin_Hubble

http://skyserver.sdss.org/astro/en/proj/advanced/hubble/conclusion.asp

Very red and far object

Origin of the UniverseThe spectral shift of light coming from distant

galaxies tells us that the universe is expanding out of a very small volume that began at most 15 billion years ago

Estimates vary according to method The universe expanded from a state of pure

energy, hydrogen atoms condensed from energy in a process called nucleosynthesis E=mc2

Origin of the Elements

• Very small volume expands “Big Bang”

• A few minutes energy cools to form H

• Hydrogen gas clouds condensed to form main sequence stars.

• H fuses to form He and heavier atoms

• “Main sequence stars” form Oxygen and Carbon.

Water = 2 Hydrogen + 1 Oxygen

H2O

Symbols for elements

Origin of Heavy Elements

• A star more than 8-20 times the mass of our sun burns faster, then expands into a red super giant star, similar to Betelgeuse.

• Pressure is high enough to also produce the heavier elements including silicon Si, magnesium Mg, iron Fe.

• Once its fuel is exhausted,

a supernova explosion occurs. http://www.solarviews.com/cap/ds/betelgeuse.htm

Main Sequence Stars

Super GiantStars

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Most rocks are made of these two

Origin of Our Solar System

• Our solar system with its abundant collection of heavier elements condensed from the gas cloud left after the explosion of a supernova.

Supernova ejects matter-rich pressure waves into space

Local concentrations of dust coalesce

Balance between gravityand solar wind

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Planetesimalsstrike growingEarth

Iron melts andbegins to sink

Lighter materialsconcentratecloser to surface

Crust andmantle

Inner core

Atmosphere

Crust

Mantle

Outer core

Liquidcore

The moon formed after a Mars-sized planet hit earth, about 4.6 bya

We got most of the core material in the exchange

DIFFERENTIATION

During coalescence:Particles assembledue to gravity – heat up

1. Rub your hands together.Motion (“kinetic”) energyis converted to heat.

Earth’s Internal Structure

• Earth’s internal layers defined by – Chemical composition– Physical properties– Deduced from Seismographs of Earthquakes– Meteorites lend support

• Layers defined by composition– Crust– Mantle– Core

Iron-Nickel Meteorite

Earth’s internal structure• Main layers of Earth are based on physical properties including mechanical strength

• Outer layers mostly Silicate Minerals: Crust and Mantle • Lithosphere (behaves like a brittle solid) Crust and uppermost mantle• Asthenosphere “weak sphere” Rest of Upper Mantle Heat softened, plastic solid • Lower Mantle Solid due High Pressures

• Inner Layers Core Iron and Nickel, outer core hotter than melting point - liquid, inner core solid due to high pressures

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CRUST

MANTLE

(least dense)

CORE(most dense)

~2900 km

~5155 km

Upper mantle

Lower mantle

Outercore

Continental crust

Oceanic crust

0 km~100 km~350 km

Lithosphere

Asthenosphere

Innercore

Conversion Factors

6370 kilometers to the center of the Earth

6370 km x 5 miles/8 km = 3981.25 miles

Earth has a radius of about 4000 miles

Note progression of densitiesOil and water

Liquid Outer Core causesMagnetic Field

Earth has a large liquid outer core, makes a magnetic field, and so a thick atmosphere

“Asthenosphere”

“Lithosphere”

The Magnetic Field protects the Atmosphere. The Atmosphere

protects Earth from most meteors

Origin of magnetic field: the liquid outer core

An Important Magnetic Field

A magnetic field once surrounded Mars. The red planet lost its protectivemagnetic field as the smaller planet cooled down more rapidly than Earth, losing its hot liquid core. Mars retains just isolated remnants of its atmosphere where pockets of relict magnetism remain.

A Perfect SpotA Perfect Spot

Earth's distance from the Sun allows Earth's distance from the Sun allows water water to exist as a to exist as a liquid. liquid.

The The biosphere biosphere of Earth has moderated the composition of of Earth has moderated the composition of the atmosphere to make it more suitable for life. Vegetation the atmosphere to make it more suitable for life. Vegetation absorbed large volumes of carbon dioxide and produced absorbed large volumes of carbon dioxide and produced oxygen Ooxygen O2 and Ozone O and Ozone O3. .

Earth's Earth's atmospheric gases atmospheric gases protect the planet from all but protect the planet from all but the largest incoming space projectiles (comets, meteorites) the largest incoming space projectiles (comets, meteorites) and ozone blocks harmful ultraviolet radiation from the Sunand ozone blocks harmful ultraviolet radiation from the Sun

The Geothermal GradientThe Geothermal Gradient The temperature gradient in the crust The temperature gradient in the crust

averages approximately 25averages approximately 25ooC per C per kilometer.kilometer.

Varies with location (higher in areas of Varies with location (higher in areas of volcanic activity) and depthvolcanic activity) and depth

Shows the interior of the planet is much Shows the interior of the planet is much hotter than the exterior. hotter than the exterior.

Volcanism an indication that heat is being Volcanism an indication that heat is being transferred from the interior toward the transferred from the interior toward the surface. surface.

Heat transfer occurs by convection, Heat transfer occurs by convection, radiation and conduction. (define)radiation and conduction. (define)

From the Asteroid Belt to Earth

• The gravitational attraction of Jupiter , or passing comets, jostles asteroids from their asteroid belt orbits causing collisions

• Sends asteroids toward the inner planets.

• Impacts with earth, moon and terrestrial planets have left scars that can still be observed today

Barrington CraterWinslow, Arizona

The Tunguska Event • Had the object responsible for the

explosion hit the Earth a few hours later, it would have exploded over Europe (most probably Scandinavia) instead of the sparsely-populated Tunguska region, producing massive loss of human life and changing the course of human history

http://en.wikipedia.org/wiki/Tunguska_event

A Dirty Comet Impact in 1908 -- No Crater

2100 km2 flattened

Comets – dirty snowballs – are jostled loose from the Oort Cloud and fall toward the Sun

K-T Mass Extinction - A Crisis in the History of Life

Cretaceous-Tertiary extinction claimed dinosaurs, flying reptiles, marine reptiles, and many marine invertebrates

Chicxulub impact structure on the Yucatan Peninsula, Mexico

65 mya this event placed dust in the atmosphere and started fires that killed 70% of all species

http://en.wikipedia.org/wiki/Chicxulub_Crater

Gravity Map

The dust is found in a thick layer worldwide, and forms the K|T boundarythe boundary between the Age of Reptiles and the Age of Mammals.

Luis and Walter Alvarez

The K\T ash layer in Alberta

Shocked Quartz

The consequences of a Chicxulub

• Powerful air blast flattens everything for thousands of square kilometers

• Massive earthquake 100 to 1000 x greater than historical times

• Deep crater 10-20 x object diameter• Massive plume of dust into atmosphere.

blocking sunlight• Lower temperatures and a short-term cooling trend. • Earth in darkness prevents photosynthesis for the next

year.• Vegetation would not survive • Colossal wildfires that would add smoke to the rapidly

darkening skies. • Giant tsunami waves with heights up to 2 miles) would be

possible from a Chicxulub-sized event in the deep ocean.

The End of the Age of Reptiles65 million Years Ago

NASA'sannualbudget fordetection ofNEOs:$3 million

One superfund cleanup $21 million

The Geology Paradigm

What is That?

Okay, that’s enough background. During WWII ships with depth sounders crisscrossed the earth’s oceans

• Alfred Wegener• Proposed hypothesis in 1915 • Published The Origin of

Continents and Oceans

• Continental drift hypothesis • Supercontinent Pangaea began breaking

apart about 200 million years ago

Continental drift: An idea

before its time

South American and African Coastlines Fit

Fossils, mountain ranges, glaciers

The revolution beginsThe revolution begins

• During the 1940s and 1950s technological advances permitted mapping of the ocean floor. Hess was captain of a minesweeper with sonar. Left it on all WWII.

• Seafloor spreading hypothesis was proposed by Harry Hess in the early 1960s.

http://www.amnh.org/education/resources/rfl/web/essaybooks/earth/p_hess.html

Remember Arthur Holmes

Harry Hess

http://www.gfdl.noaa.gov/~io/Bubble.html

Convection, the basic idea of Plate Tectonics, Atmospheric Cells, and Ocean Currents

Bubble Convection ( i.e. the lava lamp model)

Start with a hot bubble, it expands and so is less dense. It rises as surrounding dense material presses on it, especially at deeper, higher pressure, levels. When it hits a barrier it spreads, cools and becomes denser. It sinks and returns material to the start.

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Mid-oceanridge

Harry’s Idea:Sea-Floor Spreading

Convection cells in the hot mantle hit the lithosphere barrier. They spread out and cool,

pulling the lithosphere apart. New lava gets into the cracks, filling the gap, and FORMING NEW

OCEAN CRUST!

Some mineral crystals in solidifying lava align with Earth’s magnetic field. Tilt tells latitude.

Earth’s North –SouthPoles can flip. Tilt will change direction

New lava rock will have the signature of the magnetic field when it froze

How Can We Test Harry’s Hypothesis?

Paleomagnetic reversals would be recorded by lava (called basalt) at mid-ocean ridges

Fred Vine and Drummond Matthews: Harry’s idea is A TESTABLE HYPOTHESIS

New lava rock will have the signature of the magnetic

field when it froze

Maps of Magnetic Stripes in Oceanic CrustPrinceton PostDoc Fred Vine

and Drummond Matthews

Did they prove Harry’s idea?

Plate tectonics: The new paradigmPlate tectonics: The new paradigm• More encompassing theory than

Wegener’s continental drift

• Explains motion of Earth’s lithosphere by seafloor spreading (creation of new ocean floor) and subduction (destruction of old ocean floor)

• All major earth features are explained

Harry Hess’s Seafloor Spreading developed into

Here we see Divergent Margins (the Atlantic Mid-Ocean Ridge – Harry’s Sea-Floor Spreading) and

Convergent Margins (the dense Pacific Ocean Plate is being dragged under South America – called subduction zones )

The Asthenosphere boils, like soup. This moves the cold Lithosphere PLATES above

Lithosphere is "the scum floating on top of the boiling soup"

Continental Lithosphere

Oceanic Lithosphere

Subduction Zone

Asthenosphere

Divergent Boundaries (Rising Convection Currents) Mid-Ocean Ridge

Convergent Boundaries (Descending Convection Currents)

Subduction Zone

Mantle material rises, ponds under the lithosphere, spreads, pulls the lithosphere apart. Mantle minerals exposed to low pressures. Some mantle minerals are unstable at low pressures.They melt, forming lavas, which get into the cracks, and cool into basalt, the main rock of ocean lithosphere.

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NORTHAMERICANPLATE

CARIBBEANPLATE

PACIFICPLATE

COCOSPLATE

ANTARCTIC PLATEANTARCTIC PLATE

Mid-AtlanticRidge

Mid-AtlanticRidge

SOUTHAMERICANPLATE

AFRICANPLATE

ARABIANPLATE

INDIAN-AUSTRALIANPLATE

PHILIPPINEPLATE

PACIFICPLATE

FIJIPLATE

EURASIANPLATE

NAZCAPLATE

SCOTIAPLATE

90º90º 0º

0º

45º

45º

180º

0º

45º

45º

180º 180º90º 90º0º

180º

JUAN DEFUCAPLATE

Convergent plateboundaryDivergent plateboundary

Transform plateboundary

Seven or so major plates, about an equal number of small plates

Components of Plate Tectonics: there are three main types of plate marginsDivergent, Convergent and Transform

Each plate bounded by combination of all three boundary types

Divergent boundaries are located mainly along Mid-Ocean Ridges (MORs)

The East African Rift

MORs can start as rift valleys, the dry land precursor of mid-ocean ridges.

Soon enough they connect to the sea, and flood, forming a new ocean

CONTINENTAL PLATE

CONTINENTAL PLATE

Oceanic lithospherebeing subducted

(a)

Convergent Plate BoundariesIf Seafloor Spreading (Divergence) is occurring somewhere,

plates must push against one another in other areas

Subducted Ocean Plate loses water and adjacent Mantle partially melts, new buoyant magma rises to the surface, forming a

Volcanic Arc such as the Andes Mountains of South America

Rocks deformed in collision

Collisionalmountains

(b)

Collisions formed the Appalachians, and, more recently, the Himalayas and the Alps.

Suture

Once the ocean crust between them is subducted, the continents collide. Both are thick and made of buoyant (low density) minerals, so neither

continent can be subducted under the other

The collision of India and Asia produced the Himalayas

1. Subduction Zone Phase 2. Collision Phase

Convergent Boundaries

Ocean-Continent

Ocean-Ocean

Continent-Continent

TypesProducts

India

Asia

Andes, Cascades

Japan, Aleutians

Himalayas, Alps, Appalachians

Favorite quiz picture

Transform Margins accommodate movement as plates slide past one another, for example

the San Andreas Fault and between Mid-Ocean Ridge segments

Transform Plate

Boundaries

Plate Tectonics Explains It AllPlate Tectonics Explains It All• The Plate Tectonic concept caused the

realization that Earth’s many geologic features were all caused by the same process.

• We now understand mountains, volcanoes, and big earthquakes associated with, for example, the San Andreas fault.

• We understand rift valleys and how oceans form, deep ocean trenches, mid-ocean ridges, and why fossils and mountain ranges look alike across vast oceans.