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Doming along the caldera axis reduces the gradient of the Yellowstone River from Le Hardys rapids to the Yellowstone Lake outlet and ultimately causes an increase in lake level.
The magnitude 7.4 Yucca Valley quake, named the Landers earthquake for the nearest, hardest-hit town, ruptured at 5 a.m. on June 28. A second one, 6.5 on the Richter scale, hit about three hours later, 30 kilometers west at Big Bear Lake, a ski resort in the San Bernardino Mountains. News reports that day said the two quakes were "unrelated," but reports the next day said they were related. Williams explains that although technically speaking, the second may have been too far away to be called an aftershock, the two earthquakes were clearly related in that the Landers earthquake lowered the compressional stress on the Big Bear fault and allowed it to rupture. It also lowered the compressional stress across the central portion of the lower San Andreas fault. "It didn't go off, but the period of worry is not over," says Williams, who believes that the southern end will be the next big section of the San Andreas to rupture. He was concerned that slippage on the four Yucca Valley faults would set up a continuation north toward Barstow and south to the San Andreas via the Joshua Tree structure that slipped in April. If the San Andreas fault were to break as far north as the Cajon Pass (where Interstate 15 pierces the San Bernardino Mountains to connect Palmdale and San Bernardino) and south to the Salton Sea (which lies south of the Mojave Desert), Williams predicts the quake would be a magnitude 8.0 -- the Big One the experts are expecting. The Landers earthquake is providing scientists with a wealth of information. "The Yucca Valley zone is very wide and complex, with lots of large and lots of small displacements," Williams says.
Williams' theory is that the strain is heading toward the back side of the Sierras, northeast into central Nevada, where it may affect active geothermal fields. The earth's movement could enhance the production of geothermal fluids by contributing to a thinning of the crust and allowing the fluids to circulate through complex fractures. A huge strain response on a scale never seen before occurred during the 24 hours following the Landers earthquake. At the Pinion Flats Observatory researchers from UC San Diego observed a massive redistribution of strain deep in the earth's crust. For the first time, Williams says, scientists will be able to study not just how the upper 12 kilometers of brittle crust reacts, but the response of the deep crust beneath it.
Chemistry
Potentially harmful substances in some volcanic ash are the water-soluble materials called leachates, mostly acids and salts, that cling to the particles of glass and crystals. These soluble coatings are derived from the interactions in an eruption column between ash particles and gas aerosols, which may be composed of sulphuric and hydrochloric acid droplets with absorbed halide salts. It is these components that make ash mildly corrosive and potentially conductive.
The most common leachates are Cl, SO4, Na, Ca, K, Mg, and F. Other elements reported but in lower concentrations include Mn, Zn, Ba, Se, Br, B, Al, Si, Cd, Pb, As, Cu and Fe. Most of these elements and compounds are naturally present in ground and surface water but become hazardous above threshold concentrations. Finer ash is able to carry more soluble ions than coarser ash because of its larger surface area; fine ash and smaller-sized ash travel greater distances from an erupting volcano and typically extend over very wide areas than larger ash particles.
Observations from historical eruptions show that concentrations of hazardous leachates in ash decrease with increasing distance from an erupting volcano, with few examples of serious chemical contamination of portable water supplies.
Fluorine: Excess fluorine is recognized as the most hazardous leachate in water supplies, but few historical eruptions are known to have resulted in fluorine poisoning in humans. The main concern of fluorine poisioning is for livestock, which graze on ash-contaminated grass and feed.
"Consumption of water with fluoride concentration of 2-10 ppm would not be expected to cause ill health if the contamination lasted only a few days, though it would be prudent for susceptible people, mainly those with chronic sickness, to use uncontaminated water. Acute exposure to higher concentrations can cause gastrointestinal illness. Consumption of water containing greater than 1 ppm fluoride over long periods could lead to dental mottling in children and, at higher concentrations, osteofluorosis." (Baxter and others, 1982, p. 271).
Hekla, Iceland: 14 May 1970; "Local groundwater is measuring high amounts of fluorine, which is toxic to sheep and horses. Fluorine concentration in creek water has been measured at 10 mg/liter." (Smithsonian Institution Global Volcanism Program; see www.volcano.si.edu...).
Hekla, Iceland: 26 Feb 2000: "Ash from previous Hekla eruptions has often been the cause of fluorosis in grazing animals. However, during this time of the year most domestic animals are kept indoors, so fluorosis is not expected to become a problem. Freshly fallen ash was measured for soluble fluoride ions (F-). The result was 800-900 mg F/kg. Snow melted by the ash contained about 2,200 mg/l (ppm) of fluoride," (see Smithsonian Institution Global Volcanism Program; www.volcano.si.edu...).
Mount St. Helens, U.S.: 18 May 1980: After the 1980 eruption of Mount St. Helens, the amounts of water-soluble materials were apparently not large enough to significantly affect well or surface water supplies. Many laboratories performed leaching tests on a variety of ash samples, and none of the tests indicated soluble chemical contaminants at concentrations great enough to exceed the Maximum Contaminant Level (MCL) for public water supplies. The tests simulated the effects of rain falling on the ash.
Volcanic ash is the most widely-distributed product of explosive volcanic eruptions, and can disrupt vital infrastructure on a large scale. Previous studies of effects of ashfall on natural waters and water supplies have focused mainly on the consequences of increased levels of turbidity (ash suspended in water), acidity and fluoride, with very little attention paid to other contaminants associated with volcanic ash. The aims of this paper are twofold: firstly, to review previous studies of the effects of volcanic ashfall on water supplies and identify information gaps; and secondly, to propose a simple model for predicting effects of ashfall on water supplies using available information on ash composition. We reviewed reported impacts of historic eruptions on water supplies, drawing on case studies from New Zealand, Vanuatu, Argentina, the USA, Costa Rica, Montserrat, Iceland and Guadeloupe. Elevated concentrations of fluoride, iron, sulphate and chloride, as well as turbidity and acidity, have been reported in water supplies. From a public health perspective, the two main issues appear to be: (1) outbreaks of infectious disease caused by the inhibition of disinfection by high levels of suspended ash, and (2) elevated fluoride concentrations. We devised a simple model using volcanic ash leachate composition data to predict effects on receiving waters. Applying this model to the effects of Ruapehu ash, from the 1995/1996 eruptions, suggests that the primary effects of concern are likely to be an increase in acidity (decrease in pH), and increases in concentrations of the metals aluminium, iron and manganese. These metals are not normally considered to pose health risks, and are regulated only by secondary, non-enforceable guidelines. However, exceedences of guideline values for Al, Mn, Fe and pH will cause water to become undrinkable due to a bitter metallic taste and dark colour, and may also cause corrosion, staining and scale deposition problems in water tanks and pipes. Therefore, the main issues following volcanic ashfall of similar composition to Ruapehu ash are likely to be shortages of potable water and damage to distribution systems, rather than risks to public health.
Map showing location of all earthquakes in the Yellowstone National Park area from 1973 to Jan 7, 2009. The red circles are the Yellowstone Lake swarm earthquakes. All other earthquakes are shown in gray. The yellow stars are known volcanic ventsThe large gray star is the location of the M 7.5 Hebgen earthquake in 1959. The park boundary is outlined in green and the caldera is outlined in black. The earthquake locations where calculated using techniques described in
Farrell, J. M., R.B. Smith and S. Husen, 2008, Earthquake swarm identification and b-value mapping of the Yellowstone
volcanic-tectonic system, J. Vol. Geotherm. Res, (submitted).
Originally posted by Hx3_1963
reply to post by meagerhair
That doesn't sound good getting crushed...how deep is that Equipment?
Originally posted by Penster
This caught my eye.
The yellow stars are known volcanic vents
volcanoes.usgs.gov...
Didn't we have some quakes right there just yesterday?