Uplift processes

The globally S5mchronous development of erosion surfaces and slow uplift rates of shields indicates that models based on localized heating of the crust and mantle are not adequate to explain the uplift process. To produce near simultaneous surfaces on separate continents. King (1967) invoked global epeirogeny - uplift... 

There is a great deal of evidence that demonstrates that natural diamond crystals were partially dissolved, and this is summarized in Table 9.2. Special attention should be paid to the superimposed circular ditches (Fig. 9.6). This patterning may be explained by assuming that bubbles, formed by degassing during the uplifting process of the magma, adhered on the crystal surface and resisted dissolution. 

Many of the diamonds in t)q)es (2) and (3) were trapped in the uplifting process of kimberlite and lamproite magma and were brought up to the Earth s surface, whereas it is thought that those in t5q>e (1) have been brought up by a reverse sub-duction movement. 

Irregular forms of Type II crystals may represent broken forms of what were originally polyhedral forms in the Earth and became irregular either (i) by the uplifting process or (ii) due to shock received during or after mining operations. 

Minerals made of calcium carbonate are sedimentary materials, and are likely to be significant sources of fossils. Fossils tend to be destroyed during the geological processes that form igneous and metamorphic rocks. Minerals Uke limestone accumulated over millions of years at the bottom of the oceans and then rose to the surface because of plate tectonics. Because they are relatively unaltered by the uplift process, the fossils they contain tend to still be intact. 

Draft An airstream within an occupied zone that causes thermal discomfort of the occu pants due to its temperature and/or velocity. Also, the thermal uplift caused by densit) differences required to provide adequate air both for the combustion process and the removal of the products of combustion. 

Physiographic development of the surface of the earth refers to the landforms and shapes of the landscape. These surface features are subject to continuous change from constructive (e.g., uplift, volcanic activity, and deposition of sediments) and destructive (e.g., erosion) processes. Landform modifications are continuous and sequential. These modifications establish a predictable continuity that can be helpful in determining certain aspects of relative geologic ages. 

Using the rock cycle as an example, we can compute the turnover time of marine sediments with respect to river input of solid particles from (1) the mass of solids in the marine sediment reservoir (1.0 x 10 g) and (2) the annual rate of river input of particles (1.4 X lO g/y). This yields a turnover time of (1.0 x 10 " g)/(14 x lO g/y) = 71 X lo y. On a global basis, riverine input is the major source of solids buried in marine sediments lesser inputs are contributed by atmospheric feUout, glacial ice debris, hydrothermal processes, and in situ production, primarily by marine plankton. As shown in Figure 1.2, sediments are removed from the ocean by deep burial into the seafloor. The resulting sedimentary rock is either uplifted onto land or subducted into the mantle so the ocean basins never fill up with sediment. As discussed in Chapter 21, if all of the fractional residence times of a substance are known, the sum of their reciprocals provides an estimate of the residence time (Equation 21.17). 

The Fe and Mn that diffuse downward are subject to precipitation as carbonate and sulfide minerals in which the metals are present in reduced form. These minerals do not undergo any further chemical changes unless tectonic processes (uplift) cause them to come into contact with O2. As with the oxide phase, other metals tend to coprecipitate into the sulfide minerals, such as cadmium, silver, molybdenum, zinc, vanadium, copper, nickel, and uranium. 

On the early Earth, ions were mobilized from volcanic rocks by chemical weathering. Rivers and hydrothermal emissions transported these chemicals into the ocean, making seawater salty. These salts are now recycled within the crustal-ocean-atmosphere fectory via incorporation into sediments followed by deep burial, metamorphosis into sedimentary rock, uplift, and weathering. The last process remobilizes the salts, enabling their redelivery to the ocean via river runoff and aeolian transport. In the case of sodium and chlorine, evaporites are the single most important sedimentary sink. This sedimentary rock is also a significant sink for magnesium, sulfate, potassium, and calcium. 

The sedimentary and metamorphic rocks uplifted onto land have become part of continents or oceanic islands. These rocks are now subject to chemical weathering. The dissolved and particulate weathering products are transported back to the ocean by river runoff. Once in the ocean, the weathering products are available for removal back into a marine sedimentary reservoir. At present, most mass flows on this planet involve transport of the secondary (recycled) materials rather than the chemical reworking of the primary (juvenile) minerals and gases. The natirre of these transport and sediment formation processes has been covered in Chapters 14 through 19 from the perspective of the secondary minerals formed. We now reconsider these processes from the perspective of impacts on elemental segregation between the reservoirs of the crustal-ocean-atmosphere factory and the mantle. 

When humid, warm air masses are transported towards a chain of mountains by the prevailing wind systems, they are forced upwards and simultaneously cooled by the natural barrier. If, in the process, the temperature reaches or falls below dew point, clouds are formed on the windward side of the mountain range. The intensity of the precipitation triggered by this process exhibits a high spatial variability, with precipitation rates primarily dependent on the uplift distance, uplift velocity and... 

Ruddiman WF, Raymo ME, Prell WL, Kutzbach JE (1997) The climate uplift-connection. In Tectonic Uplift and Climate Change. Ruddman WL (ed) Plenum Press, p 3-15 Salomans W, Goudie A, Mook WG (1978) Isotopic composition of calcrete deposits from Europe, Africa and India. Earth Surf Processes 3 43-57... 

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