CEE 1030 1nd Edition Lecture 19: Deserts and WindsOutline of Last Lecture I. GlaciersII. Features of glaciers and glacial movementIII. ReviewIV. Glaciers in relation to landformsa. Glacial erosionb. Glacial landformsc. Glacial depositsV. Glaciation effectsVI. Review, cont.Outline of Current Lecture I. Distribution of landII. Key questions in desertsa. What is a dry climate?b. Where are deserts located?c. How does erosion occur?III. Types of desertsIV. Wind depositsV. Types of sand dunesVI. ReviewCurrent LectureI. Distribution of landa. Dry regions cover 30% of Earth’s land surfaceb. Deserts are not measured by temperature, but by drynessII. Key questions in desertsa. What is a dry climate?i. Dry climate: where annual precipitation is less than water loss by evaporationii. Desert: arid, driest of dry climate zonesiii. Steppe: semi-arid, marginal zoneb. Where are deserts located?i. Low-latitude desertsii. Bands of semi-arid climate at Tropics of Cancer and Capricorniii. Mid-latitude deserts: occur in areas sheltered by mountainsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.iv. Continental interior deserts: form on inland of large land masses1. Wind moving onto continent loses most of its moisture by precipitationc. How does erosion occur?i. Weathering in arid climates1. Most weathered debris in deserts consists of unaltered rock and mineral fragments from mechanical weatheringii. Most desert erosion is a result of running wateriii. Deserts characterized by dry washes: dry channels of ephemeral streams that contain water only during heavy rainfalliv. Precipitation is rare in the desert, usually only through very heavy rainv. Sparse vegetation and poorly integrated drainage systems contribute to runoffvi. Flash floods commonvii. Desert rivers1. Most permanent rivers in the desert originate outside of the desert2. Infiltration and evaporation deplete streamsviii. Interior drainage system1. Most arid regions have streams that don’t flow to ocean, but to a basinix. Early landscape evolution1. Landscape evolution driven by tectonic uplif2. Running water erodes3. Streams transport and deposit large amounts of sediment4. Playa lakes: form in flat central area of undrained desert basins5. Bajada: apron of sediment along a mountain front6. Inselbergs: isolated mountain remnantsx. Wind in the desert1. Wind also works to erode, transport, deposit sediments2. Differences between water and aira. Wind less capable of picking up coarse particlesb. Wind is not confined, can spread sediment over a large area3. Wind transporta. Suspended load: fine particles transported within the airb. Saltation: transport of particles through a series of bouncesc. Bedload: particles moved across a ground surface (also called a creep)xi. Wind erodes by abrasion1. Yardangs: wind sculpted ridges2. Ventifacts: stones with flat facesIII. Types of desertsa. Hot and dry: warm all year, very hot in summer, precipitation evaporates in the airb. Semiarid: summers moderately long and dry, winters with low precipitationc. Coastal: cool winters followed by moderately long, warm summersd. Cold: short, moderately warm summers, long cold winters with snowfallIV. Wind depositsa. Types of wind depositsi. Dunes: mounds and ridges of sand from the wind’s bedloadii. Loess: extreme blankets of silt from the wind’s suspension loadb. Sand dune: hill or ridge of wind-deposited sandi. Most dunes have asymmetrical profileii. Bedload accumulates in wind shadowiii. Sand moves up windward slope by saltation, accumulation at the crestiv. When leeward side of dune becomes steeper than the angle of repose of sand, crest collapses down the slipfaceV. Types of sand dunesa. Shapes and sizes vary according to:i. Wind directionii. Wind velocityiii. Availability of sandiv. Amount of vegetationb. Transverse dunes: long ridges oriented perpendicular to the prevailing windc. Longitudinal dunes: long ridges of sand oriented parallel to prevailing windd. Barchan dunes: sand dunes shaped like crescents with tips pointing downwinde. Parabolic dunes: crescent-shaped dune, similar in shape to barchans but tips point in to windVI. Reviewa. Wind lifs fine, loose particles from the desert floor and leaves behind larger particles. This process is called