Plate tectonics
Download
1 / 143

Plate Tectonics - PowerPoint PPT Presentation


  • 337 Views
  • Updated On :

Plate Tectonics. The Unifying Theory of Geology. The 4 “Big Ideas” in Geology. The Rock Cycle (Friday’s lecture) By the mid-1700s Antiquity of Earth - “Deep Time” (Wednesday’s Lecture) By the early 1800s, millions of years Faunal Succession (Fossil Record – Core 6) By mid-1800s

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Plate Tectonics' - Anita


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Plate tectonics l.jpg

Plate Tectonics

The Unifying Theory

of Geology


The 4 big ideas in geology l.jpg
The 4 “Big Ideas” in Geology

  • The Rock Cycle (Friday’s lecture)

    • By the mid-1700s

  • Antiquity of Earth - “Deep Time” (Wednesday’s Lecture)

    • By the early 1800s, millions of years

  • Faunal Succession (Fossil Record – Core 6)

    • By mid-1800s

  • Plate Tectonics

    • By late 1960s


The big ideas earth is old and dynamic l.jpg

The Big Ideas  Earth is Old and Dynamic

Rather than Young and Static


Recall the scientific method l.jpg
Recall: The Scientific Method

  • Observations

  • Hypothesis (a testable explanation)

    • Includes testing by prediction

  • More observations (testing)

  • If ALL observations fit ---> Theory


The ancient greeks l.jpg
The Ancient Greeks

  • Knew that Earth was round (not discovered by Columbus) by 300 B.C.

  • In fact Eratosthenes (ca. 250 B.C.) measured its circumference

PhotoNot Available


Early observations l.jpg
Early Observations

  • First European explorers started to gather knowledge on world geography

  • Early 1500s: E.g., Magellan & da Gama


Early observations7 l.jpg
Early Observations

  • Francis Bacon (1561-1626) first noted how coasts of Africa and South America fit.

Yikes!!!…

bacon!


Slide8 l.jpg

Today it’s

known:

Fit best

along their

continental

shelves


The 1800s l.jpg
The 1800s

  • Better maps available

  • Some people proposed that all continents could fit together

  • In 1872, British Challenger began mapping ocean floor by soundings

  • Similarities in rocks of NW Europe and NE America were discovered


Slide10 l.jpg

About 1910, the Mid-Atlantic Ridge was discovered


Paleontology l.jpg

Paleontology

The study of fossils


Evidence from paleontology l.jpg

Evidence from Paleontology

Similar fossils in

South America and Africa


Glossopteris a seed fern whose seeds are too large to be carried far by wind l.jpg
Glossopteris, a seedfern whose seeds are too large to be carried far by wind


Mesosaurus a fresh water reptile that couldn t swim across the open sea l.jpg
Mesosaurus, a fresh water reptile that couldn’t swim across the open sea


Paleoclimatology l.jpg

Paleoclimatology

The study of ancient climates


Slide16 l.jpg

Evidence of glaciers


Slide17 l.jpg

Evidence of glaciers


In south america africa india and australia at same time the northern hemisphere had lush swamps l.jpg
in South America, Africa, India, and Australia...At same time the Northern Hemisphere had lush swamps...



Slide20 l.jpg
Coal

  • Deposits found in Antarctica brrrrr….

  • Coal requires a warm, lush climate ===>

  • What’s Antarctica like today? ===>


Paleomagnetism l.jpg
Paleomagnetism

  • Magnetic minerals in molten rock align with Earth’s magnetic field


Paleomagnetism22 l.jpg
Paleomagnetism

  • When igneous rock cools, magnetism is “frozen in”, like little compasses...


Polar wandering apparent change in position of poles over time l.jpg
Polar Wandering = apparent change in position of poles over time


Polar wandering l.jpg
Polar Wandering

  • Different continents indicate different position of North Pole - very strange...

  • Only logical explanation is that the CONTINENTS have moved since the rocks were formed


Wegener and continental drift l.jpg
WEGENER and CONTINENTAL DRIFT

  • In the 1910s Alfred Wegener put all these pieces of evidence together and made the hypothesis of CONTINENTAL DRIFT...

  • The Origin of Continents and Oceans (1915)


Continental drift l.jpg
CONTINENTAL DRIFT

  • When Wegener proposed to fit the continental shelves together, rather than the coastlines, we got a better fit for all modern continents...


Slide27 l.jpg

All continents have moved to their present positions from one “supercontinent” he called PANGAEA

- 200 Ma


Scientific consensus is that earth is about l.jpg

Scientific Consensus is that Earth is about one “supercontinent” he called

4.5 billion years old

(4.5 Ga)


Breakup of pangaea l.jpg
Breakup of Pangaea one “supercontinent” he called


1912 1945 l.jpg
1912 - 1945 one “supercontinent” he called

  • A few geologists looked for more evidence during this period...

  • Seismologists began studying the deeper layers of the earth and discovered a dense mantleand liquid outer core.


Wwii and sonar l.jpg
WWII and SONAR one “supercontinent” he called

  • Sonar, developed to find enemy subs, was used in the decade after WWII to map the deep sea floor...


Sonar l.jpg
SONAR one “supercontinent” he called

  • Previously, most geologists thought the sea floor was rather flat and featureless

  • They were wrong...

  • A diverse topography was discovered


Topography of the sea floor l.jpg
Topography of the Sea Floor one “supercontinent” he called


Topography of the sea floor34 l.jpg
Topography of the Sea Floor one “supercontinent” he called

  • Researchers found an undersea mountain range 40,000 miles long.

  • And a trenches seven times deeper than the Grand Canyon.

  • Even more striking were the geophysical findings...


Some geophysics l.jpg

Some Geophysics one “supercontinent” he called

Thousands of drilling samples were taken...


Geophysics l.jpg
Geophysics one “supercontinent” he called

  • Paleomagnetism in the deep sea floor rocks indicated that many episodes of magnetic reversals had taken place...


These reversals occur in parallel paired bands on opposite sides of a mid ocean ridge l.jpg
These reversals occur in one “supercontinent” he called parallel paired bands on opposite sides of a mid-ocean ridge.

Radiometric dating showed the rocks get older the farther you get from the ridge.


Sea floor spreading l.jpg
Sea-Floor Spreading one “supercontinent” he called

  • In 1962, these data were collected into a theory called SEA-FLOOR SPREADING

    • New crust forms at mid-ocean ridges...

    • Oceanic crust pushes outwards from the ridge and (perhaps) takes the continents along


Earthquakes and volcanoes l.jpg
Earthquakes and Volcanoes one “supercontinent” he called

  • Seismology is the study of earthquakes


Remember the tsunami l.jpg
Remember the one “supercontinent” he called Tsunami?


Earthquakes and volcanoes41 l.jpg
Earthquakes and Volcanoes one “supercontinent” he called

  • Data indicate that earthquakes and volcanoes do not occur at random locations, rather...



E g pacific ring of fire l.jpg
E.g., Pacific “Ring of Fire” trenches and mid-ocean ridges...


Seismology studies l.jpg
Seismology studies trenches and mid-ocean ridges...

  • located a zone of weakness where seismic waves travel more slowly

  • It was called the asthenosphere.

  • The rigid lithosphere sits on top of this


Finally a unifying theory l.jpg
Finally, a unifying theory trenches and mid-ocean ridges......

  • In 1968, seismologists at Columbia put all the evidence together and came up with the theory of PLATE TECTONICS...

  • This combined the sub-theories of CONTINENTAL DRIFT and SEA-FLOOR SPREADING


Plate tectonics46 l.jpg
PLATE TECTONICS trenches and mid-ocean ridges...

The rigid upper 35 miles or so of the earth (lithosphere) is broken up into a dozen or so plates, which can slide around on the zone of weakness.


Mechanism l.jpg
MECHANISM trenches and mid-ocean ridges...

Current idea: plates move as a result of mantleconvection, driven by earth’s internal heat


Consequences of plate tectonics earthquakes volcanoes mountain ranges l.jpg

Consequences trenches and mid-ocean ridges... of Plate TectonicsEarthquakesVolcanoesMountain Ranges

Why it’s a

“Unifying Theory”


First a few definitions l.jpg
FIRST, A FEW DEFINITIONS... trenches and mid-ocean ridges...


Types of plate boundaries l.jpg

Types trenches and mid-ocean ridges...of Plate Boundaries


Slide68 l.jpg


Slide69 l.jpg

Great trenches and mid-ocean ridges...

RiftValley

of Africa


Slide70 l.jpg



Slide72 l.jpg


San andreas fault l.jpg
San Andreas Fault trenches and mid-ocean ridges...


Volcanoes l.jpg
Volcanoes trenches and mid-ocean ridges...

  • Are associated with divergent and convergent plate boundaries ...

  • Why ?


Slide75 l.jpg

Pacific rim trenches and mid-ocean ridges...

“Ring of Fire”

Convergent

and

Divergent boundaries


Earthquakes l.jpg
Earthquakes trenches and mid-ocean ridges...

  • Are associated with ALL boundary types ...

  • Why ?


Mountain building l.jpg

Mountain Building trenches and mid-ocean ridges...

“Tectonics”


Appalachians l.jpg
Appalachians trenches and mid-ocean ridges...

Started forming 400 million years ago (400 Ma)

Cumberland Gap


Rockies l.jpg
Rockies trenches and mid-ocean ridges...

Started forming 60 Ma

Maroon bells, CO


Himalayas l.jpg
Himalayas trenches and mid-ocean ridges...

Started forming 30 Ma


Folded strata l.jpg
Folded trenches and mid-ocean ridges...Strata

Rockies 

Appalachians 


Mountain building and plate tectonics l.jpg

MOUNTAIN trenches and mid-ocean ridges...BUILDING and PLATE TECTONICS


Convergent boundary l.jpg
CONVERGENT BOUNDARY trenches and mid-ocean ridges...

Complex mountain system develops---> Continent Grows


Example the andes l.jpg
Example: The Andes trenches and mid-ocean ridges...


The andes l.jpg
The Andes trenches and mid-ocean ridges...


Geocycles l.jpg

Geocycles trenches and mid-ocean ridges...

Rocks, Water, Air


Geocycles88 l.jpg
GEOCYCLES trenches and mid-ocean ridges...

  • Recycling of matter at or near earth’s surface

  • Rock cycle

    • Lithosphere

  • Water cycle

    • Hydrosphere

  • Weather and Climate

    • Atmosphere


First the rock cycle l.jpg

First, the trenches and mid-ocean ridges...ROCK CYCLE


4 concentric layers l.jpg
4 trenches and mid-ocean ridges... concentric layers

  • Inner core (solid)

  • Outer core (liquid)

  • Mantle (gooey in places)

  • Crust (solid) 3-40 miles thick


What is the lithosphere and what are the plates l.jpg
What is the Lithosphere and what are the “Plates”? trenches and mid-ocean ridges...

  • The crust, plus the upper 40 miles of the mantle, form the lithosphere, broken into plates which slowly slide around on the zone of weakness…


Igneous rxs fire formed l.jpg
IGNEOUS RXS trenches and mid-ocean ridges...“Fire-formed”

  • Liquid rock is called magma or lava, depending on amount of dissolved gas

  • INTRUSIVE - cooled under surface

    • Examples: Granite, Gabbro

  • VOLCANIC - cooled at surface

    • Examples: Basalt, Obsidian, Scoria


Sedimentary rx settling l.jpg
SEDIMENTARY RX trenches and mid-ocean ridges...“Settling”

  • Clastic - formed from pieces “clasts”, which come from the weathering and erosion of other rock.

    • Examples: Shale, Sandstone, Conglomerate

  • Bio-chemical and Organic

    • microskeletons, e.g. in coral reefs:Limestone

    • Salts in stagnant pools, e.g., Halite

    • Organic - decayed remains of plants:coal


Metamorphic rx changed form l.jpg
METAMORPHIC RX trenches and mid-ocean ridges...“Changed form”

  • Depends on original rock type and amount of heat and pressure

  • Shale ----> Slate or Schist (more heat)

  • Granite or “dirty” sandstone ---> Gneiss

  • Sandstone ----> Quartzite

  • Limestone ----> Marble


Igneous rxs and absolute dating l.jpg
IGNEOUS RXS and trenches and mid-ocean ridges...ABSOLUTE DATING

  • Some igneous rocks can be radiometrically “dated” – i.e., have an ABSOLUTE AGE assigned...


On the other hand sedimentary rocks l.jpg

On the other hand… trenches and mid-ocean ridges...SEDIMENTARY ROCKS

Are most likely to contain fossils


But sedimentary rocks l.jpg

But, SEDIMENTARY ROCKS trenches and mid-ocean ridges...

Can only be “relatively dated”…


Relative dating l.jpg
RELATIVE DATING trenches and mid-ocean ridges...


Relative dating100 l.jpg
RELATIVE DATING trenches and mid-ocean ridges...


Deep time l.jpg

DEEP TIME trenches and mid-ocean ridges...

Oceans vs. Puddles


Air and water l.jpg

AIR trenches and mid-ocean ridges...and WATER


Water facts l.jpg
Water Facts... trenches and mid-ocean ridges...

  • 70 % of Earth’s surface is covered by H2O

  • 70 % of human body’s weight is H2O

  • Water can exist in 3 states earth’s surface

    • exists only as solid and vapor on Mars

    • only vapor on Venus


Mars is too cold l.jpg
Mars is too trenches and mid-ocean ridges...cold...


Venus is too hot l.jpg
Venus is too trenches and mid-ocean ridges...hot...


Earth is just right l.jpg
Earth is trenches and mid-ocean ridges...just right...


More water facts l.jpg
More Water Facts... trenches and mid-ocean ridges...

  • Water freezes at 0 degrees Celsius and boils at 100 degrees Celsius

    • This is higher than similar substances because of hydrogen bonding

    • Water is most dense at 4 oC. This explains why ice floats, which prevents lakes from freezing solid in Winter


Hydrogen bonding l.jpg
Hydrogen Bonding trenches and mid-ocean ridges...

........O H ........

/ \ /

H H ---- O

| | \

O O H .........

/ \ / \

H H H H .........

| | | |


Water l.jpg
Water... trenches and mid-ocean ridges...

  • Its heat capacity is higher than similar substances

    • “A watched pot never boils.”

  • Moderates Earth’s temperatures

    • Compare San Francisco and St. Louis


Slide110 l.jpg
AIR trenches and mid-ocean ridges...

  • Main gases in present atmosphere: Nitrogen (78%), Oxygen (21%), and Argon (0.9%), variable amounts of water vapor

  • Average sea level atmospheric pressure is 14.7 pounds per square inch and decreases with altitude


Distribution of earth s water and air l.jpg

DISTRIBUTION trenches and mid-ocean ridges...of EARTH’SWATER and AIR


Origin l.jpg
Origin trenches and mid-ocean ridges...


Origin113 l.jpg
Origin trenches and mid-ocean ridges...

  • How: Impact of IcyComets and Degassing of volatiles ... bottle

  • Earth’s atmosphere was forming 4.4 to 4.0 Ga

  • It then (probably) consisted mainly of water vapor, carbon dioxide, ammonia, methane (Some controversy)


Mt erebus antarctica l.jpg
Mt. Erebus, Antarctica trenches and mid-ocean ridges...


Brief history l.jpg
Brief History trenches and mid-ocean ridges...

  • Icy Comet impacts ---> add H2O to atmosphere and down to about 70km

  • Earth cools ---> Water condenses

  • Lots of rain; Volcanoes add CO2

  • Most of CO2 dissolved in oceans

  • Photosynthesizing organisms evolve

    • CO2 + H2O ------> C6H12O6 + O2


The water cycle l.jpg

The Water Cycle trenches and mid-ocean ridges...

How Earth’s water and air interact ...

Natural “recycling” process


The water cycle117 l.jpg
The Water Cycle trenches and mid-ocean ridges...


Zones of concentration l.jpg

ZONES OF CONCENTRATION trenches and mid-ocean ridges...

Of natural waters


Zones of concentration119 l.jpg
ZONES OF CONCENTRATION trenches and mid-ocean ridges...

  • Marine (saltwater)- The oceans contain over 97 % of earth’s water -- salt water

  • Brackish (mixture of salt and fresh):

  • Found in estuaries, where fresh and salt water meet

    • Important to aquatic life

    • 3rd most productive ecosystem

    • Example: Chesapeake Bay


Fresh water l.jpg
Fresh Water trenches and mid-ocean ridges...

  • Less than 3 % of earth’s water is fresh

  • Glaciers contain over 75 % of Earth’s fresh water, but this source is not usable by biota


Fresh water123 l.jpg
Fresh Water trenches and mid-ocean ridges...

  • Lakes and rivers contain less than 1 %

  • Groundwater (including soil moisture) accounts for the remaining 24 %

  • If all Earth’s water fit in a gallon jug, there would be one tablespoon of available fresh water


Structure of the atmosphere l.jpg

Structure trenches and mid-ocean ridges...of the Atmosphere

Layers classified by temperature changes ...


The atmosphere l.jpg

The Atmosphere trenches and mid-ocean ridges...

All weather occurs in the troposphere = “churning sphere”


Convection causes the churning l.jpg
Convection trenches and mid-ocean ridges... causes the “churning”

Temperature

decreases

with altitude


Convection in humid air l.jpg
Convection in Humid Air trenches and mid-ocean ridges...


Thunderhead l.jpg
Thunderhead trenches and mid-ocean ridges...


Stratosphere l.jpg
Stratosphere trenches and mid-ocean ridges...

  • The ozone layer is contained in the stratosphere...

  • No “churning” because of a temperatureinversion, i.e.,

  • Temperature increases with altitude...


Slide130 l.jpg

A trenches and mid-ocean ridges...

l

t

i

t

u

d

e

Stratosphere --->

Troposphere --->

Temperature


The ozone layer l.jpg
The Ozone Layer trenches and mid-ocean ridges...

  • Ozone, O3 , is an air pollutant in the troposphere, but in the stratosphere protects from UV radiation :

  • O3 + UV --------> O2 + O

  • Chlorine radicals (like from CFCs) interfere with this process:

  • Cl + O --------> ClO


Slide132 l.jpg

WEATHER trenches and mid-ocean ridges...and CLIMATE

- Atmosphere Geocycles


Coriolis effect l.jpg

Coriolis Effect trenches and mid-ocean ridges...

Caused by an unattached atmosphere over a rotating Earth


Coriolis effect134 l.jpg
Coriolis Effect trenches and mid-ocean ridges...


Coriolis effect on winds l.jpg
Coriolis Effect on Winds trenches and mid-ocean ridges...


Coriolis effect on winds136 l.jpg
Coriolis Effect on Winds trenches and mid-ocean ridges...


Slide137 l.jpg

ACTUAL trenches and mid-ocean ridges...

NON-ROTATING


Prevailing winds l.jpg
PREVAILING WINDS trenches and mid-ocean ridges...

  • The direction the winds blow most of the time ...

  • Changes temporarily due to weather systems ...

  • In the middle latitudes (30o- 60o), the prevailing winds are from the west.

  • These affect climate as we shall see in a moment ...


Prevailing winds139 l.jpg
PREVAILING WINDS trenches and mid-ocean ridges...


Ocean currents l.jpg
OCEAN CURRENTS trenches and mid-ocean ridges...

  • (Surface) currents caused by prevailing winds and Coriolis Effect ...

  • They play a major role in redistributing earth’s heat ...

  • They are called warm or cold, compared with other water at that latitude ...

    • Example: The Gulf Stream is a warm current.


Slide141 l.jpg

OCEAN CURRENTS trenches and mid-ocean ridges...


Effects on climate l.jpg
Effects on Climate trenches and mid-ocean ridges...

  • Many factors affect climate

  • Prevailing winds and ocean currents are only two of these

  • Example: Why is the weather in Paris more pleasant than in Quebec City ?

  • Gulf Stream + Prevailing westerlies