GEOL110_Natural Hazards CH8
GEOL110_Natural Hazards CH8 GEOL 110
Long Beach State
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This 5 page Class Notes was uploaded by Doris M on Sunday April 24, 2016. The Class Notes belongs to GEOL 110 at California State University Long Beach taught by Ewa Burchard in Spring 2016. Since its upload, it has received 7 views. For similar materials see Natural Disasters in Geology at California State University Long Beach.
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Date Created: 04/24/16
Soil Notes -The more moisture in soil, the more hazardous it is Venice: 4mm/y San Venice -constructed in the lagoon -any weight on the soil can cause compression -Venice is subsiding -the pumping of ground water contributes tot eh subsiding -in the san Joaquin valley there needs to be a lot of water pumped because of the agriculture, similar to Venice -pumping ground water causes the above ground to sink -high tide enters thru the lagoon outlets -lagoon: shallow ocean water separated by barrier islands -coast is subject to flooding -Venice is sinking slowly -sea level rising -Mose project: a system of 4 barriers. Mobile barriers able to separate venice from the sea. A flexible defense system. If water rises too high the gates are raised. Opposes high tides. Defends the ecosystem. When there is more water, theres is more water pressure and the gas turns on and fills in those barriers, the barriers become lighter and rise. Can be raised up to 2 meters. If the sea level rises, the barriers can also rise -a solution to Venice sinking Venice is Sinking -sinking aka subsiding 1.5mm / yr -surrounded by canals and so venice is prone to flooding -warning ssytem consists of warning sirens -human response- raising buildings Soil -soil is the material that comes from rocks -when it is eroded, it stays on the rocks, if it is not removed by water or wind -agriculture: the material that supports vegetation or plants -in engineering: it is the material that is easily moved -different shades of soil mean different water level in the soil -not all locations will have well developed soil -O horizon, A horizon and E horizon: zones of leaching -B horizon: zone of accumulation -C horizon: weathered rock -R horizon: bedrock -not all horizons have the same thickness Soil and Hazards -soil: solid earth that has been altered by physical, chemical, and organic processes such that it can support rooted plant life. Soil is any solid earth material that can be removed without blasting -weathering: the physical and chemical breakdown of rocks into smaller pieces and its first step in soil development -transported soil: weathered material transported by water, wind,or glaciers and then modified in its new location Ex. Fertile soils formed from glacial deposits in Am midwest Climate -if there is more vegetation, the O horizon will be thicker -if there is a think slope, more soil will be transported Organic processes -affects the A horizon because of the high organic material Soil Horizons -soils can move horizontally or vertically -O: organic materials -more organic material present -color- dark brown or black -A: mineral and organic material -minerals and organic materials -color-light black to brown -leaching: the process of dissolving, washing, or draining earth materials by percolation of ground water or other liquids -occurs in the A horizon and moves clay and other material such as iron and calcium to the B horizon -E: forms zone of leaching with the A layer -has no organic material -easier to be washed out -the layer for which fine materials are leached B: enriched in clay, iron oxides, etc, resulting from leaching -contains clay -where clays and other rocks are washed out from the upper materials and deposited in the B layer -can be reached in clay materials -Bt: enriched with clay materials -Bk: accumulation of calcium carbonate C: partially altered (weathered) parent material -weathered bedrock R: unweather parent material -unweathered bedrock Water in Soils-the Properties of soil -saturated soil: water is present and water holds the soil. Pushes particals away but also holds the soil -moist soil: soil can expand Soil Erosion -soil can be moved quickly and easily by wind and water Soil Erosion as a hazard -if there is more water, it holds the soil -if you move water, the soil compacts -as long as ground water is present in the caverns, it will hold everything in place -surface subsiding: karst Karst -present in lime stone caves Subsidence -when the ice thaws, the soil will be compacted which can lead to subsiding -earthquakes- movement of magma -magma draining: decreases the land can can cause land sunsidasence -when earth shakes, water can flow up and can cause particles to move down and replace water- liquefaction Mass wasting -creeping-the freezing of water pushing soil particles up -causes movement of soil Karst -the distribution of vegetation says where more water is present Sinkholes -land subsides quickly -formed by natural conditions of the bedrock Karst topography -present in southern and eastern states ex. Florida Louisiana Sinkhole -drill punctured a hole in a salt mine -the water started filling in the salt mines -water dissolves salt -the pressure of the water made the whole a larger -caused by an engineering error -didn’t map the mines correctly -didn’t think about what would happen if they hit the salt mines -changed the type of fish in the lake -parts of lands were lost -properties were lost -no one died Chihuahua Cave Mines -contains a mine -mining is a common job for that area with a lot of challenges -crystal cave discovered -cave is hot and deadly- humidity -in the heat of the cave, cells an die -the humidity prevents evaporation -crystals break easily Karst -Karst topography: underground dissolution of limestone by acidic ground water creating landscapes of caves and sinkholes -tower karst-When land subsides into the caves -limestone towers -streams appear near the tower -sink holes and caverns are reserve waters Thermokarst -permafrost: sediment remains frozen throughout the yr -causes subsidence and structural damage -what happens when water is removed? -natural resources open the caves -when water is present there is pressure -when water is present, the land will be elevated -when water is removed, particles collapse -when the clay is present in the soil, the soil has the tendency to absorb water -organic soils: soils that contain organic material -can create swelling Earthquakes -when there is a subduction zone, there is an uplift of the continent or ocean floor -subsidence can be cause by earthquakes Lava tube -lava tube: forms when molten lava drains out from underneath cooled surface lava -leaves void near the surface that is susceptible to collapse Swelling: the and increases in size -ex. Permafrost -destruction of sidewalks Geologic Regions at Risk fpr Subsidence and Soil Volume Change -karst topography composes about 10% of Earths surface -northern states affected by permafrost -Organic rich soils Ex. New England Effects -problems -sinkholes are easily contaminated -contaminated water supply -surface contamination with slow precipitation San Joaquin Valley -an agricultural area using a lot of ground water for irrigation -in some seasons, too much water is being pumped -if there is over pumping, layers of the clay can shrink and the whole area can collapse -once something subsides, it compacts and doesn’t change and go back Soil and Hazards -3 important properties of soil -soil color -texture -structure -red soil is transported clay in the B horizon -soil fertility: refers to the capacity of the soil to supply nutrients needed for plant growth. -water may flow vertically of lateral through pores of soil -flow is saturated (all pore space filled with water) -flow can also be unsaturated (pore space is partially filled with water) Subsidence and Soil Volume Change -subsidence: a type of ground failure characterized by nearly vertical deformation, or the downward natural processes, human act, or combo of the 2 -most subsidence is caused by underground dissolution, lowering groundwater levels, fluid pressure on sediment, thawing permafrost, low sediment on plains, earthquakes causing volcanic eruptions
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