EES 215

Lecture 1

Goals of course: discussion of processes at surface of earth; make-up of crust, hydrosphere and atmosphere; dynamic processes in these three subsections; interaction between lithosphere, hydrosphere and atmosphere; influence of human activities on status of surface of earth.
 

The earth: two scales - microscopic - macroscopic:

Earth is a planet in solar system
       specific characteristics:                Fig. 1
size: two groups:


Earth is largest of terrestrial planets, relatively high density (5,500 kg/m3)

Distance to sun:
third closest to sun; elliptical orbit around sun with small differences in the two axes of ellipse; rotation of earth around axis which is slightly tilted with respect to plane of rotation around sun - important for energy balance at surface of earth; causes for change in day and night; seasons; difference in climatic zones.

Important features of earth: energy flux from sun allows presence of atmosphere, hydrosphere; surface temperature around 10oC (variations between -40oC and 50oC, i.e., between freezing and evaporation of water - water is predominantly in liquid state at surface of earth; relatively small variations in surface temperature (day and night; seasons) - tempered by presence of atmosphere (and hydrosphere) - feed back mechanism

Microscopic scale: Element distribution

Universe (solar system): Observations:             Fig. 3

Predominance of hydrogen and helium; decrease in abundance from light to heavy elements; local maxima and minima; even-numbered elements preferred over odd-numbered
Potential reasons: building block system: larger nuclei are formed by fusion of smaller nuclei - probability for forming nuclei decreases with increasing size
stability rules: symmetry prefers even numbered nuclei; 'magic' numbers (2,8,10,...82,126...): local maximum at 4He; Fe; Pb; local minimum at Li, Be, B

Earth: Observations: absence of H, He; eight elements make up more than 99%; dominance of Fe; O; Si
Crust: same elements, but in different proportions, make up 99% of crust           Fig. 4

Explanations: Absence of light elements due to size of earth - too small to hold on to light elements
differentiation in the earth: different subsections of the earth: core - mantle - crust
 processes active in differentiation: gravity - heavy elements are dominant in core and compatibility: classification of elements into siderophile, chalcophile, lithosphile and atmosphile elements
Siderophile: compatible with metallic iron (e.g. Fe; Ni, Au)

Chalcophile: compatible with S (e.g. Cu; Ag; Fe)

Lithophile: compatible with O (e.g. Na; Si; Fe)

Atmophile: gaseous (e.g. noble gases; N)

inner core: siderophile
outer core: chalcophile
mantle and crust: lithophile
atmosphere: atmophile

make-up of crust:
classifications of minerals
 

SUMMARY

Factors influencing our environment:

Earth as planet:
             distance from sun: energy flux;
                         T distribution
                         presence of hydrosphere; atmosphere; feedback mechanism
              rotation around sun; earth's axis:
                         year; day
                         seasons (ellipticity of rotation; tilted axis)

Composition of Earth (distribution of elements):
            absence of H; He: high density (solid surface)
            dominance of O in atmosphere; lithosphere
            presence of O (and H2O): life