1654: Archbishop Ussher -- dated formation of Earth.

4004 BC on October 22, at 9:00 AM. Noah's flood: 11-18-2349 BC.
 

1780's: French paleontologists, Baron Georges Cuvier and Alexander Brogniart, expounded the

Principle of Catastrophism.
 
 
 

1795: James Hutton established Principle of Uniformitarianism -- the same physical and chemical laws that we recognize in action today have operated throughout the history of the earth.
 
 
 

Atmosphere

- Composition: 78% N₂ , 20% O₂ , 1% Ar, trace CO₂, CO, SO₂, N₂O, O₃

- Transports water - mostly in the troposphere (lowest 13 km), jets fly just above this.

- was very different in the past - low O₂, lots of NH₃, strong changes in chemical reactivity

Biosphere

- distribution: 90% plants, 10% others, <<1% "higher" animals

- range: nearly everywhere on surface and water, mostly in warm, wet, nutrient rich areas

- effects: limestone deposition, O₂ in atmosphere, source of coal, oil, natural gas
 

Hydrosphere

- distribution: 94% Ocean, 4% groundwater, 2% glaciers, <<1% lakes, rivers, etc.

- distribution varies through time, chemistry varies through time early, but not much lately

- effects:

transport of solar heat from tropics to poles (climate control),

erosion,

weathering

transport of sediments, salts

aids metamorphism, melting of rocks

no continents if there were no water (water required for many minerals)
 

Geosphere

- soil, sediment, rock => on down to the core

- igneous: crystallize from melt

- sedimentary: settling of sediments, crystallization from water

- metamorphic: altered rocks at high temp & pressure

Hydrologic Cycle

- Leonardo da Vince (~1500) gave first cogent description of the hydro cycle

- Perrault and Mariotte (late 1600's) first quantified the cycle for the Seine River in France

=> precipitation in basin = river discharge + spring discharge ( + evaporation)
 
 
 
 
 
 
 
 
 
 
 
 

- key points of the hydrologic cycle:

1. evaporation from ocean and evapo-transpiration from land (plants)

2. clouds - potential energy

3. precipitation - kinetic energy. Worldwide, kinetic energy is equivalent to 90 Niagara Falls that extend half a mile into the sky.

4. glaciers and snow - temporary storage of water

5. infiltration, runoff, groundwater

Rock Cycle
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Compositional zonation of the Earth.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Earth = 6371 km radius

Core = about half way out (2883 depth) - Fe, Ni composition

Mantle = middle portion - Peridotite composition (an igneous silicate rock)

Crust = outermost portion (chalk width on the board)

Two types:

Continental - 10-75 km thick, average 35 km, Granitic composition

Oceanic - 5-20 km thick, average 7 km, Basaltic composition

Physical or Behavioral zonation of the outer earth.
 
 
 
 
 
 
 
 
 
 
 
 
 
 

-- Lithosphere - cold, strong outer portion. Crust and uppermost mantle. High viscosity.

-- Asthenosphere- warm, weak underlying zone. Upper mantle. Low viscosity. Very Actively convecting.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

I. Heat in the Earth.

A. Earth is hot inside. The temperature gradient (geothermal gradient) is an average 25°/km.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

B. Two ways heat moves through a body:

Conduction - heat transfer without deformation of the body. Ex. Frying pan handle.

Convection - heat transfer with deformation of the body. Ex. Boiling water.

C. Convection occurs in Gases, Liquids and Solids. Depends on the Viscosity of the body -

Viscosity is resistance to flow.

High Viscosity = Material Flows Slowly...

Low Viscosity = Material Flows Easily...

Temperature is a primary control on viscosity for most all earth materials.

Higher temperatures yield weaker materials - lower viscosity.

D. Why is the earth hot?

1)

2)
 
 

The temperature of the earth is hot enough to cause convection in both the molten iron core and in the overlying mantle.

Plate Tectonics = Scum of the Earth.

Lithosphere is a "thermal boundary layer" between hot asthenosphere and cold air/water at the surface.
 
 
 

Convection in the mantle breaks up the scum (lithosphere) and pushes the little pieces around.

Lithospheric pieces are strong enough to behave as rigid plates, playing bumper cars. We call this "plate tectonics".

(Tectonics = study of earth deformation)

Soup:
 
 
 
 

Each lithospheric plate may consist of:

A) Continents or parts of continents, or...

B) Oceans or parts of oceans, or...

C) Both.
 

Three Types of Plate Boundaries:

Divergent - plates moving apart. Many small volcanoes. Mid-Ocean Ridges and Continental Rift zones.
 
 

Convergent - plates moving together. Mountains, Volcanoes and Earthquakes. Subduction zones are where one plate is pulled beneath another because it is heavier.
 

Transform - plates slipping past each other laterally. San Andreas fault. Earthquakes.

Divergent margins => new lithosphere forms.

Convergent margins => old, cold lithosphere returns to the mantle.

Map of Plates of the World:
 
 
 
 
 
 
 
 
 
 

Revisit Rock Cycle:
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Why Plate Tectonics?

- Primary control on the shape and character of the earth's surface (mountains, oceans, ......)

- Primary control of major earth processes (volcanoes, earthquakes)

- Primary control on distribution of rock types around the world (ig, met, sed, and how much of each).

- Significant control on distribution of earth resources (oil, coal, many economic minerals).

- Provides a testable framework for describing earth history.

For Wednesday, MINERALS! Read Chapter 2.  Know the whole chapter before your second GLY 111 lab.