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DESERT DUST

DESERT DUST. YOU HAVE A HANDOUT THAT PROVIDES AN OVERVIEW OF THE SUBJECT – READ IT AS WELL AS MY BRIEF SUMMARY DUST STORMS COMMON PHENOMENON IS ARID AND SEMI-ARID REGIONS OF THE WORLD. DESERT DUST. WORLD WIDE PICTURE MAP ON PAGE 1 OF HANDOUT

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DESERT DUST

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  1. DESERT DUST • YOU HAVE A HANDOUT THAT PROVIDES AN OVERVIEW OF THE SUBJECT – READ IT AS WELL AS MY BRIEF SUMMARY • DUST STORMS COMMON PHENOMENON IS ARID AND SEMI-ARID REGIONS OF THE WORLD

  2. DESERT DUST • WORLD WIDE PICTURE • MAP ON PAGE 1 OF HANDOUT • SHOWS MAJOR DIRECTIONS AND DISTANCES OF TRANSPORT OF DUST • SAHARAN DUST TO THE CARIBBEAN • SEE FIGURE 2 OF HANDOUT • VOLUME OF DUST PER YEAR • ESTIMATED AT 500,000,000 TONS • OFTEN NEGLECTED PART OF TOTAL SEDIMENT TRANSPORT ON THE EARTH • SUBJECT OF GREATLY INCREASED INTEREST AND STUDY

  3. DESERT DUST • VOLUME (CONT) • WHAT DOES THIS MEAN/ • UNIT COAL TRAINS W/ 120 CARS OF 120 TONS OF COAL EACH • EACH TRAIN CARRIES 14,400 TONS • 500,000,000 DIVIDED BY 14,400 = 34,722 TRAINS • EACH TRAIN 1.26 MILES LONG • 1.26 TIMES 34,722 = 43,750 MILES • EARTH CIRCUMFERENCE = 24, 901 MILES • 1.76 TIMES AROUND THE EQUATOR

  4. DESERT DUST • SOURCE AREAS • 36% OF EARTH’S SURFACE (ARID AND SEMI-ARID REGIONS) • SAHARA • ARABIAN PENINSULA • SUDAN • CHINA • AUSTRALIA • US • ARGENTINA AND CHILE • ETC. – SEE LIST ON P.2 OF HANDOUT

  5. DESERT DUST • SOURCES • LARGE DUST STORMS ORIGINATE OVER ALL DESERTS • LARGE DUST STORMS ARE ALSO ASSOCIATED WITH AREAS OF SEMI-ARID CLIMATE WHICH PERIODICALLY BECOME ARID – WEST TEXAS, RUSSIAN STEPPE, INDIA

  6. DESERT DUST • SOURCES • DUST DEVILS • SMALL LOCAL FEATURES UP TO WHAT AMOUNT TO TORNADOES • HABOOBS (Arabic term) – HUGE STORMS LIFTING DUST UP TO 2500 METERS • DUST STORMS OBSERVED ON SATELLITE IMAGERY

  7. DESERT DUST • SOURCES • DUST FROM LOCAL IN SITU WEATHERING OF ROCKS • ALSO ALLUVIUM FROM WADIS, ARROYOS, AND PLAYAS • AGRICULTURAL FIELDS • CONSTRUCTION SITES, ETC.

  8. DESERT DUST • TRANSPORT • FACTORS THAT INFLUENCE INITIATION OF DUST MOVEMENT • WIND VELOCITY • SURFACE ROUGHNESS • PARTICLE SIZE • VEGETATION OR LACK THEREOF • MOISTURE CONTENT • TEXTURE • MINERALOGY

  9. PARTICLE SIZE • VARIES BUT MOST LESS THAN 50m • COMMON DUST DEVIL SIZE IS 5-50M • VERY FINE FRACTION CAN BE HELD IN SUSPENSION FOR QUITE SOME TIME • SEE GRAIN-SIZE CURVES OF FIGURE 3. • AEROSOL DUST – WHAT IS IT? • IMPORTANCE • SIZE FRACTION

  10. DESERT DUST • DISTANCE OF TRANSPORT • ACROSS THE ATLANTIC • GOBI DESERT TO ALASKA • GOBI DESERT TO CANADA • AUSTRALIA TO INDIAN OCEAN AND ALSO INTO PACIFIC • SAHARA DUST TO ISRAEL (25,000,000 TONS?) • US. DUST FROM WEST TO GEORGIA, 2400 KM.

  11. DESERT DUST • MINERALOGY • MAINLY QUARTZ (65%0) • FELDSPAR (0-20%) • CALCIUM AND MAGNESIUM CARBONATES (UP TO 35%)

  12. DESERT DUST • ROLE OF DUST IN GEOLOGIC PROCESSES • OCEAN SEDIMENTS • DESERT VARNISH • CALICHE • SOIL FERTILITY

  13. DESERT DUST • DUST AND MAN • PATHOGENS • POLLUTION • DESERTIFICATION • AUTOMOBILE ACCIDENTS • CLIMATIC EFFECTS

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