Cycles of the Earth

• Hydrological Cycle and Weather• Climate• Chemical Cycles• Ice Ages• Rock Cycle• Geological Time Scale

Hydrological Cycle

Taxonomy of Clouds

Luke Howard (1772-1864), Britain

Fitzroy and the Weather Forecast• In the British Navy and

responsible for weather reports

• Coined phrase Weather Forecast

• Convinced that barometer readings foretell tomorrow’s weather

• Committed suicide after he was ridiculed by the press and the Admiralty dropped the need for forecasting

Vice-Admiral Robert Fitzroy (1805-1865), Britain

High and Low Pressure

Cyclonic Circulation

Collision of Air Masses

Ocean Currents

Movement of the Air

Hadley cell named for George Hadley (1685-1768) tried to explain why trade winds seemed to flow to the west

Climate Conveyor

Global Climates

El Niño & Gilbert Thomas Walker

1868-1958; England & India

Chemical Cycle: Carbon

Chemical Cycle: Oxygen

Chemical Cycle: Nitrogen

Ice Ages

Evidence of Glacial Action

• Moraines• Glacial Till and Flour• Erratics• U-Shaped Valleys

Jean Louis Rodolphe Agassiz (1807-1873); Switzerland and USAProposed Europe had been subjected to an Ice Age (1837-1840)

Svante August Arrenius

• Developed theory of Greenhouse Effect to explain Ice Ages

• 1896 calculated how changes in CO2 concentration could change climates

1859-1927; Sweden

James Croll

• Used the formulas developed by Le Verrier on planetary orbital variations

• Developed a theory about orbital variations influencing the amount of snow

• Orbital eccentricity should cause ice ages on a 22,000 year cycle

• Largely dismissed by end of the 19th Century 1821-1890; Britain (Scotland)

Milutin Milanković

• Canon of the Earth’s Insolation: climates of the planets

• Explanation of changes in Earth’s climate by interactions of three planetary cycles 1879-1958 (a Serb) born

in Kingdom of Hungary and died in Yugoslavia

Milanković Cycles• Eccentricity of earth’s

orbit (Kepler’s theory) has a 100,000 year cycle from 0.005 (nearly circular) to 0.058 (mildly eliptical)

• Axial tilt has a 41,000 year cycle (tilt changing from 22.1o to 24.5o )

• Precession has a 23,000 year cycle (suggested by Hipparchus in 130 BCE)

Inference of Climate Based on Temperature Proxies

PollenTree ringsIce coresRatio of oxygen isotopesCoralsDiatoms and foraminifera

Rock Cycle1. Magma2. Crystallization (freezing)3. Igneous rock4. Erosion5. Sedimentation6. Sediments & sedimentary rock7. Tectonic burial and

metamorphism8. Metamorphic rock9. Melting

Defined by Hutton and Lyell and modified by John Tuzo Wilson (1908-1993), Canada.His Ph.D. advisor: Harry HessRock cycle explained by erosion and action of plate tectonics

Using Steno’s Laws, attempt to interpret geological strata by relative time

Jean Léopold Nicolas Frédéric Cuvier& Alexandre Brongniart

• Together studied geology of Paris basin• Defined concept of faunal succession• Theory of cycle of repeated catastrophes

Cuvier(1769-1832) France

Brongniart(1770-1847)France

William ‘Strata’ Smith• Surveyor• Strata of coal

mines and canals• Used principle of

faunal succession to define layers

• Life’s work: Geological map of England and Wales

1769-1839, England

A plate of Smith’s fossils

Roderick Impey Murchison, 1st Baronet

• Independently wealthy, urged by Humphry Davy to turn his focus to science

• Became interested in the geology of Wales, England, Alps, Russia, Scotland

• Helped define the Silurian, Devonian, and Permian Systems 1792-1871, Britain (Scotland)

Adam Sedgwick• Cambridge University faculty

(ordained in the Church of England)

• Defined Cambrian system• Worked with Murchison to

define Devonian in England and on the system in the Alps

• Charles Darwin was his student who helped to define the sequence of Cambrian rocks in Wales

1785-1873, England

Arthur Holmes• Pioneer of radiometric dating

(Uranium-Lead method). Wrote this in a book by the time he was 24.

• Provides absolute time to strata

• Showed the earth was more than 1 BY old (most geologists had accepted that the earth was only 100 MY old)

• Completed the Geological Time Scale in 1944

1890-1965; England

Geological Time Scale