Field Trips BRING LUNCH & drink, Bathrooms few & far between. In lieu of lab on 2 April Pick which trip If you can't make either one, see Kite http://www.weather.com/weather/weekend/uswv0507?from=search Cheat River Cacapon Mtn Cacapon Mountain - Saturday 2 hours 15 minutes from White Hall ~ some hiking on gentle-smooth & ruggedbouldery terrain. working trip: downloading data loggers & numerous measurements. Departure 9:00 a.m. and return about 6:00 p.m., may be later if science takes longer Dress for the weather (Berkeley Springs, WV) for at least 4 hours conducting field work. Trivial "extra credit for attending both trips 1
Sunday Cheat River including, Muddy Run, the 1840s Virginia Iron Furnace, Albright in the record 1985 flood, and large boulder transport in the Cheat Narrows. Blackwater Falls? Short-distance hiking on steep bouldery terrain. Departure 9:00 return by 6:00 p.m. 2007 Test 2 Results A = 77 B = 66 C = 55 Total Class GEOL non-geol 77.30 78.00 76.08 D = 44 So 77.43 Jr Sr Raw Score T2 vs T1 Avg Score 75.33 78.85 +4.61 Dust Storm, Tunisia, (D. Heron Photo) Aeolian Geomorphology 2
Many of The Images Used in This Presentation Were Obtained From a Web Site Constructed by Duncan Heron, Duke University Http://www.Geo.Duke.Edu/geo41/win.Htm Aeolian Processes What Causes Wind? Pressure Gradients What Causes Differences in Air Pressure? Temperature, Moisture Pressure Gradients Drive Wind 3
Coriolis Effect Deflects Flow Direction Jet Stream L L H L H Why Deserts? Rain Shadows Global Circulation Patterns 4
Orographic Effects Rain Shadow Global Circulation Cold Sun Hot Equator Hadley s Model Cold Air Sinks Sun Hot Air Rises Equator 5
Hadley s Model Cold Air Sinks Sun Hot Air Rises Equator Simple Convection Cell in Each Hemisphere Better Model 50-60 o Sun Hot Air Rises 20-30 o Equator 3 Convection Cells in Each Hemisphere Gas Laws PV = nrt 6
Wet, Wet, Cool Cool Better Model Sun Warm, Dry Air Hot, Wet Air Cool, Wet Air 50-60 o 20-30 o Equator Cold, Dry Air 3 Convection Cells in Each Hemisphere Better Model Dry, Cold Wet, Cool Dry, Hot Sun Wet Hot Dry, Hot 3 Convection Cells in Each Hemisphere Dry, Cold Better Model Easterlies Westerlies Sun Easterlies Equator 3 Convection Cells in Each Hemisphere 7
Summer Model Easterlies Sun Westerlies Easterlies Thermal Equator Real Equator Winter Model Easterlies Westerlies Sun Easterlies Real Equator Thermal Equator Global Circulation 8
Distribution of Deserts http://pubs.usgs.gov/gip/deserts/what/world.html Aeolian Sediments Aeolian Sediments Tractive Load: Surface Creep (Larger Clasts) Saltation: Mostly Msd-Fsd, Can Be Crs Silt to Pebble (Rare) 9
Ripples (D. Heron Photo) Topsail Beach, NC (D. Heron Photo) Suspension Load (Silt + Clay = Dust) Gravity Settling (Fallout!) Condensation Nucleii in Precip. 10
Lag Gravel Ventifacts Aeolian Depositional Systems Most Aeolian Landscapes Begin as Fluvial Landscapes Source: Old Floodplains Barren Rock Surface Site of Deposition Cover sands (often glacio-eolian) 11
Deflation Hollows - Reg Surface Armor Rock Varnish Hammada Yardangs = Streamlined Erosional Forms Erg = Dune Field Ripples, Dunes Draa Reg, Pre-Sahara Desert (D. Heron Photo) Desert Pavement 12
Antarctica: Ventifacts & Desert Pavement Yardangs (Hammada) John Stimac Eastern Illinois University http://www. ux1.eiu.edu /~cfjps/1300/ deserts.html Uluru (= Ayers Rock) a Yardang http://www.qantasvacations.com/images/pg33ayqsunset.jpg 13
Yardang? http://www.hermes-group.com/photos/cairo/sphinx.jpg Dune Field, Victoria Valley, Antarctica Glacier Reg Transverse Dunes Erg Dune in Later Slide Cross-Bedding in Dunes Grain Flow Down Slip Face Stoss, Lee 14
Sand Dune, Victoria Valley, Antarctica Wind Direction Windward Face of Dune, Victoria Valley Lee Slip-Face of Dune, Victoria Valley 15
Longitudinal: Stripes of Erg Separated By Reg Low Sand Supply, High Wind Velocity ( Unidirectional ) Longitudinal Dunes, Australia (NASA photo) Longitudinal Dunes, Arabian Peninsula (NASA Photo) 16
Transverse Dunes: High sand supply, low wind velocity Stopped Here 30 March Transverse Dunes, Algodones Sand Sea, SE Calif. (Photo by P. Kresan, U. of AZ, USGS) Transverse Dunes, Bogue Bank, NC (D. Heron Photo) 17
Barchan Dunes: Transitional between. Longitudinal & Transverse Barchan Dune John Stimac Eastern Illinois University http://www.ux1. eiu.edu/~cfjps/ 1300/deserts.html Megabarchan John Stimac, Eastern Illinois U. http://www.ux1.eiu.edu/ ~cfjps/1300/deserts.html 18
Star Dunes: Multi-Directional Winds Star Dune, Namib Desert (G. Gerster photo, NASA) http://pubs.usgs.gov/gip/deserts/types/ Star Dune, Namib Desert, G. Gerster photo, http://pubs.usgs.gov/gip/deserts/dunes/) 19
Star Dunes John Stimac Eastern Illinois University http://www. ux1.eiu.edu/ ~cfjps/1300/ deserts.html Ripples on Dune in Gran Desierto, Sonora, Mexico (P. Kresnan photo, U of AZ, USGS) http:// pubs.usgs. gov/gip/ deserts/what/ Parabolic Dunes with Blow Outs Sechura Desert, Peru http://www.tec.army.mil/terrain/desert/lifsheet/lipara.htm 20
Parabolic Dunes Rajasthan (Thar) Desert India and Pakistan Coppice Dune = Windshadow (D. Heron Photo) Coppice Dunes, Assateaque Island, VA S. Kite Photo, 19 March 2005 21
Matanuska Valley Loess, W. Huff Photo http://tvl1.geo.uc.edu/ice/image/propro/32.html Loess: silt mantle "typical" Missouri River bluff 10s of m at bluff, 1-2 m 50 mi East Illinois Loess Thickness Illinois State Museum http:// www.museum. state.il.us/ exhibits/larson/ loess_map.html 22
Missouri- Mississippi River System Loess Maximum Extent of Late Wisconsin Laurentide Ice Sheet ~14,000-20,000 C-14 Years B.P. Loess S. Kite Photo, Jan 1977 Loess on Outwash Terrace, New Zealand Loess Hills, Iowa 23
Loess Bluff, Wildwood, Missouri http://www.medulogic.com/caulks/loess.gif photo by C.M. Woodruff 24