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