Origin and Evolution of Earth Research Questions for a Changing Planet (2008) / Chapter Skim
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4 Hazards and Resources
4 Hazards and Resources
Pages 95-122
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From page 95... ...
The deleterious to humankind but are intrinsic to Earth imperative for improved predictive power is escalated and probably inseparable from its habitability. Both as human populations increasingly concentrate in arof these geological phenomena are catastrophic in the eas prone to earthquakes and volcanic eruptions.
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From page 96... ...
The goal of earthquake prediction is to specify where Most earthquakes occur at plate boundaries, and the and when a significant earthquake will occur. Where type of boundary plays a role in controlling the nature future earthquakes will occur is largely understood, with of earthquake activity.
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From page 97... ...
Intraplate earthquakes elevated fluid pressures, accelerating deformation and are not readily explained by plate tectonics. Some occur frictional heating, and mineral phase changes (Kirby within broad plate boundary deformation zones, such et al., 1996)
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From page 98... ...
Just as plate tectonics explains where most earthquakes Earthquake predictions are commonly classified by occur, it has much to say about how often they occur. time frame.
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From page 99... ...
Paleoseis 3. Early warning that seismic waves from a develop- mology -- the investigation of individual earthquakes ing event will arrive in seconds, ideally enabling an alert in the geological record -- provides critical information to be issued before damaging strong ground motions begin.
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From page 100... ...
This suggests that strain is accumulating on the San Andreas fault in this region, where no large earthquake has occurred in over 250 years. (CCF = Coyote Creek fault, EDM = Electro-optical Distance Measurement, SCEC = Southern California Earthquake Center, SCIGN = Southern California Integrated GPS Network, SHF = Superstition Hills fault)
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From page 101... ...
. Static stress changes over such distances thereafter earthquake rupture becomes self-sustaining, are negligible, but dynamic stress changes transmitted then earthquake prediction will be practically impos- by seismic waves have been documented in the 1999 sible.
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From page 102... ...
The probability of Earthquake? strong ground motions is commonly calculated using probabilistic seismic hazard analysis.
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From page 103... ...
FIGURE 4.5 The ground motion intensity thresholds at which precariously balanced rocks, such as the one shown at left, would be toppled provide an important test on ground motion exceedence probabilities determined from probabilistic seismic hazard analysis. SOURCE: |
From page 104... ...
Used with permission. tion of strong ground motions through simulations is What Is the Role of Slow Earthquakes?
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From page 105... ...
The slow earthquakes occur on the down-dip extension of the fault that ruptured in the 1946 earthquake.
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From page 106... ...
It has also led generated some of the largest known landslides (Moore to a few successful predictions of volcanic eruptions et al., 1994) , resulting in waves as high as 300 m above (e.g., 1991 eruption of Mount Pinatubo)
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From page 107... ...
Magma produced in subduction zones chain, which are located above deep mantle plumes. typically holds 10 to 100 times more of these volatile Less common, although more visible and hazardous components than magma formed at midocean ridges to human populations, are eruptions of volcanoes that or in mantle plumes.
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From page 108... ...
The search for trigger mechanisms plume at about 0.2 km3/yr, but some erupts through the has focused largely on earthquakes and tides. However, Mauna Loa volcano and the submarine Loihi volcano, some volcanic eruptions might be controlled by effects which are also active.
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From page 109... ...
HAZARDS AND RESOURCES 109 BOX 4.1 Monitoring Volcanoes The primary goal of volcano monitoring is to track the movement of magma beneath a volcano and thereby predict when, and how violently, it will erupt at the surface. Three common signals are used to monitor magma movement: 1.
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From page 110... ...
The geo- The largest eruptions documented in the geological record logical record provides information on the recurrence were 10 to 100 times larger than the Mount Mazama eruption. rates and magnitudes of large volcanic eruptions.
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From page 111... ...
Both of these categories performance computation holds forth the prospect of of societal concern -- resources and environmental making physics-based simulations of earthquake strong impacts -- are likely to increase in urgency in the future, ground motion. For all forms of earthquake prediction, and hence there is a continuing effort to improve access it is important to find ways to validate new techniques to underground resources, to maintain or manage existas they are developed.
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From page 112... ...
At larger scales, Earth's subsurface is composed issues associated with fluids in shallow crustal environ- of a variety of rock types, with greatly varying porosity ments also apply to deeper-Earth processes, and many and permeability, that are further complicated by faults of them also overlap with issues of earthquake predic- and fractures. tion, climate prediction, the evolution of continents, the When a rock medium is not granular but crystalbehavior of volcanoes, the formation of ore deposits, line, the pore space is typically not visible to the naked and the properties of Earth materials.
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From page 113... ...
The most include multiphase flow in complex geometries and familiar interaction is adsorption, or ion exchange, by microfluidic experiments, both of which can address which ions carried in solution in water are adsorbed and the roles of chemical transport and pore structure on desorbed from mineral surfaces. This process, which chemical reactions.
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From page 114... ...
. Copyright 2005 by Elsevier Science and Technology Journals.
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From page 115... ...
Figure 4.11 shows an stored in the ground produce heat, and both models and example of tomographic imaging, which can assess the experiments show that this heat will generate groundwa- connectivity of pore spaces or determine in situ spatially ter convection, boiling, mineral dissolution and precipita- distinct densities. Such imaging provides a powerful tion, as well as potentially corrosive conditions around the new tool for understanding the spatial characteristics waste canisters themselves (see Box 4.2)
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From page 116... ...
Conceptual model of processes in a fracture within volcanic tuff above a heat source with the properties of a radioactive waste container. Temperature is highest at the bottom of the fracture, nearest the heat source, and decreases upward.
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From page 117... ...
Also, the chemical reactions that are significant at geological timescales proceed at ultraslow rates (Question 7) , and it is obvious that the factors that control these rates are not the same as those FIGURE 4.11 Tomographic image of residual fluid saturation that control laboratory reactions that proceed a million in a sintered bead pack after free drainage.
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From page 118... ...
Current feasible options for geological sequestration include oil and gas reservoirs, coal beds, and saline formations (i.e., saline aquifers and brine-saturated sedimentary rock)
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From page 119... ...
We are living on a planet that we have availability and quality may alter the living patterns of "engineered" over the millennia. Humans have caused human populations in the future, but by how much is massive changes in the shape of landscapes as well as virtually unknown (IPCC, 2007b)
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From page 120... ...
For most abundant and important Earth fluid, and includes example, global warming brings permafrost melting in steam, hydrocarbons, liquid and gaseous carbon dioxide, polar regions, along with a range of hydrological, eco- other organic liquids, and multiphase fluids (gas plus logical, and geochemical changes (Chapin et al., 2006)
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From page 121... ...
For example, the release of water from reservoirs could be designed to mimic important natural functions, such as sediment transport, recruitment of riparian vegetation, and fish reproduction. As we learn more about the long-term consequences of sediment depletion in downstream rivers and coastal environments, we can take action to compensate.
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From page 122... ...
Only by building by new experimental tools that can illuminate what and skillfully using such models will we be able to make happens at the microscopic scale on mineral surfaces, informed decisions about the land and resources that new geochemical and geophysical field techniques, and support humankind and all life on Earth.
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