Geo Chap 13

Geo Chap 13 - March 6, 2008 Chapter 13; Page 1 Geological...

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March 6, 2008 Chapter 13; Page 1 Geological Catastrophes: Chapter 13 I. Severe Weather A. Causes about 75% of yearly deaths and damages from natural disasters B. More people killed usually by severe weather than by earthquakes, volcanoes, mass movements combined C. From 1980 to 2005, U.S. had 67 weather-related disasters causing more than $1 billion (each) in damages D. Total more than $556 billion II. Extreme Heat A. Long or short timescales 1. Long timescale: a) Plate movement, oceans opening and closing large regions may be cut off from moisture, turn into desert conditions 2. Short timescale: a) Changes in jet stream, atmospheric convergence zones may keep moisture away for many years drought conditions 3. Shorter timescale: a) Heat wave III. Drought and Famine A. Times of abnormal dryness in region, without usual rain B. Expected rains do not arrive vegetation begins to die food supplies shrink famine C. Tends to drive people apart rather than bring together D. Early stage: food available but inadequate 1. Lose up to 10% body weight, still alert and vigorous E. Advanced stage: body weight decreases by about 20%, body reduces activity levels, apathy F. Near-death stage: 30% or more body weight lost, indifference to surroundings and others G. U.S Dust Bowl (1930s) 1. Several years of drought turned grain-growing central U.S. into dust bowl 2. Position of jet stream caused upper-level, high-pressure dry air to sink hot, dry winds killed plants and eroded soil into dust clouds 3. Drought began in 1930 4. Dust storms increased in 1934, 1936 5. Blame mistakenly put on farmers for plowing up native grasses a) May have exacerbated situation b) Droughts typical but infrequent in North America IV. Heat Wave A. Heat is biggest killer of all severe weather B. Heat Wave in Chicago (July 1995) 1. Strong high-pressure ridge sat over hot, humid air mass at surface for three days
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March 6, 2008 Chapter 13; Page 2 2. Upper-level wind-flow path causes anticyclones. Mid-continent high blocks northward flow of moist gulf air 3. Heat records broken, with high maximum and minimum temperatures (no cooling at night) 4. Deaths occurred for days after—465 deaths over two weeks C. Europe’s Heat Wave (2003) 1. Summer brought record breaking heat waves (of last 150 years) 2. Delayed recognition of number of deaths— over 35,000 3. City areas are urban heat islands, with night-time temperatures up to 5.5 o C higher than surroundings 4. Heat waves will occur more frequently as climate warms V. Midlatitude Cyclones A. Northern Hemisphere cyclone : counterclockwise air mass rotating around low- pressure core B. Large scale: trough (or dip) in jet stream juxtaposes northern cold front and southern warm front C. Northeastern U.S.: low-pressure system moving up Atlantic coast draws northern cold air, moisture from east north east VI. Initiation of a Low Pressure Cell A. Warm air moving east against old air causes shear rotation B. Warm air pushed north over the front to the east, causing development of a warm
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This note was uploaded on 04/09/2008 for the course GEOL 20 taught by Professor Steidl during the Winter '08 term at UCSB.

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Geo Chap 13 - March 6, 2008 Chapter 13; Page 1 Geological...

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