What 41. is the "moment" of an earthquake? How is it calculated?
Solution to Richter problem: "Moment Magnitude scale" Hough: "moment = torque" Moment = fault area * slip * shear resistance
o Bigger the fault area, bigger the earthquake o Bigger the slip, bigger the earthquake o Bigger the resistance, bigger the earthquake
42. Which earthquake scale is based on approximate intensity? The On this scale, what does a VI or XII mean?
Modified Mercalli Scale
Minnesota; The type of soil near the Mississippi River in Memphis could be a problem in the event of an earthquake. earthquake forecasts are worse than today's weather forecasts, because earthquakes are predicted based on historical records and it is impossible to predict earthquakes far in advance.
44. Today's
43. Which of the following locations is LEAST at risk for earthquakes? Northern
45. What's a volcano? Where are they? Why there? What comes out? Where does that come from?
Top end of a rising narrow region of magma coming up from asthenosphere and upper mantle 1300 on Earth, 600 active; 70 in North America! Located along o subduction boundaries where tectonic plates collide (Japan, Philippines) o spreading sea floors or rifts (E. Africa) o Isolated "hot spots" = plumes of rising magma (Hawaii)
What Kinds of Volcanoes Are There?
EFFUSIVE: fluid low-viscosity lava oozes out gently from upper mantle, in great volumes o Shape: shield volcano, gentle slope.
Also: "Flood basalts"
EXPLOSIVE: Gooey magma in subduction zones chokes pipe, mountain blows up, "pyroclastics."
o Why gooey? High in silica and aluminum. Perhaps due to grinding away/merging of continental & oceanic crusts in subduction zones? o Shape: tall coneshaped mountain. Caldera forms if summit collapses inward after eruption.
46. What's a flood basalt?
Huge regions of effusive basaltic lava flows Nothing comparable to it today NW U.S. Columbian Plateau: 2-3 km thick! Deccan Traps of India: 2x size of Columbian Plateau! Siberian Traps: double the size of Deccan Traps! Ontong Java Plateau: bigger than Siberian Traps! Some still think that these incredible eruptions affected Earth's climate to extent that they wiped
out dinosaurs. More likely an asteroid impact, but this stuff's nothing to sneeze at.
47. Which volcano buried Pompeii? Which U.S. volcano exploded in 1980? Which one caused the "Year without a Summer" ?
o Vesuvius, Italy, 79 A.D.: destroys Pompeii
In late August 79 A.D., the ancient Roman city of Pompeii was buried under the ash of the volcano Vesuvius. The eruption wasn't big enough to change world climate, but it killed 20,000 people in Pompeii, including the famous nature historian Pliny the Elder. o Tambora, Indonesia, 1815: causes "Year Without Summer" across Europe and North America due to reflection of sunlight by sulfuric acid droplets launched into stratosphere by volcano!
Increases albedo of Earth by 1-2% until drops fall out after a few years. o Mount St. Helens, Washington state, 1980: puny by
comparison, but gets great U.S. press
48. Can volcanoes affect global climate? If so, do they make it warmer or cooler? How is it that they affect climate? Yes;
They make it cooler by releasing sulfur which combines with water making sulfuric acid and these gases reflect sunlight away. Possibly changing the albedo of the earth for a while.
49. True; Some volcanologists have taken rafting excursions on acid sulfuric lakes. Pyroclastic flow is a hot flow of gas, ash, and rock.. a rushing fire "storm" downhill.
50. What are two main types of weathering of rocks? Which one is essential in creating a karst landscape?
Physical and Chemical. Chemical weathering is essential in creating a karst landscape.
51. What rock type is necessary for karst topography? What type of karst topography can you go "spelunking" in?
Limestone is necessary for karst topography. You can go "spelunking" in caves. longest cave is in Mammoth Cave, Kentucky. "Tower Karst" is in China.
53. What's a stalactite? What's a stalagmite? Where would you find them, specifically? 52. Where is the world's longest cave? In what nation is "tower karst" topography? World's
Caves form just beneath water table, then drop in water table exposes them drip-drip of solution and solidifying of precipitate causes stalactites from ceiling, stalagmites on ground
54. What is a mass movement? Mass
movement applies to any movement of a body of material, such as rocks, propelled and controlled by gravity. A fast, wet one is called Mudflow. A fast, hot, wet, volcanic one is called this Indonesian name: Lahar. A slow, dry one is Soil creep. One that occurs with snow is Avalanche. Homo sapiens
55. The "premier geomorphic agent of our time" may well be what?:
56. What did coal originally start out as, 300 million years ago? What is the fastest-growing energy source world wide? What is the latest innovation in coal mining? Does it have any environmental consequences?
In the beginning (circa 300 million years ago), plants in swamps, e.g. peat bog. Coal is the fastest growing energy source. Mountaintop removal: few dangers of deep mining, but permanent change of landscape, and where does all that mountain go? Into the valleys! Large impacts to plants, animals, rivers, water quality, houses...
57. "Fluvial" means what? "Eolian" means what? What's the largest river in the world in terms of volume? Why isn't it the Nile? Fluvial
is from the Latin "fluvius" meaning "river", stream-related processes are termed fluvial. The Amazon River is the largest by volume. Eolian means wind. Its an exotic river so it flows through a lot of desert and evaporates along the way.
58. If the discharge of a river increases, how does this affect the river's: width, depth, velocity? Think in terms of weather safety!
More discharge means a wider, deeper, faster river.
59. How does sediment get transported in a river? How does the wind blow sand along? How are they similar/different?
Rivers carry sediment and rocks downstream in a variety of ways:
Suspension and saltation: in the flow; bouncing along the bottom. Remember these for when we talk about sand in the wind! Some rivers carry more stuff than others! Text: first Spanish explorers to visit the Grand Canyon reported that they were kept up at night by the thundering sound of boulders tumbling along streambed of the Colorado River... solution, saltation, suspension... Wind is carried by saltation and suspension also.
60. Why isn't Tallulah Falls a premier regional tourist attraction anymore? Why doesn't sediment reach the
river dammed by Georgia Power in 1913, despite fierce environmental efforts to save falls. Today's falls are generally just a trickle compared to 1900. IT doesn't reach the Colorado River delta because of damns.
Colorado River delta?