Continental relief

The potential negative feedbacks tend to stabilize atmospheric C02 and 02 concentrations in the long term. However, the processes represented by boxes in Fig. 6.5 are the result of tectonic activity and so are not controlled by feedbacks. They have the potential to disrupt the carbon cycle severely, as considered in Section 6.3. As indicated in Fig. 6.5, oceanic circulation can influence the C cycle in complex ways via its influence on climate, through its impact on heat distribution over the surface of the Earth and the rate and net direction of C02 exchange with the atmosphere. Similarly, continental relief and distribution have an effect on the climate through their influence on winds and currents. All these factors are investigated in Section 6.3.1. 

Erosion of the high parts of the continental relief produces the terrigenous (land-derived) particulate (clastic) sediments (18.5E9 Mg/yr Lisitzin, 1991) and the dissolved fluvial load (4.4E9 Mg/yr), transported to the upper shelf level by water. In addition, minor quantities of wind-blown (aerosols) and ice-rafted sediments (cryosols) are also transported to the... 

For flow tested combinations, see a few typical data in Table 7-12. Note, for example, that using a Continental disk reverse acting knife blade rupture disc with a Crosby JOS/JBS pressure relief valve that the combined effect is to multiply the rated capacity of the Crosby valve by a multiplier of 0.985 for a set pressure in the 60-74 psig range... 

The following examples explore how paleoaltimetry data may provide critical information about the evolution of mean elevation, averaged relief, and erosion from different models of continental deformation. However, I consider only changes in elevation, relief and erosion that may be predicted by tectonic models and neglect the influence that climate forcing or erosion related feedbacks could exert on such predictions. As discussed previously, the influence of climate, erosion and related feedbacks on tectonic deformation is important and should not be ignored. However, to consider all the complexities of potential interactions on the elevation record is beyond the scope and focus of this paper. In order to best illustrate the relationships between deformation mechanics and elevation, I review a few example elevation histories predicted by several commonly-cited tectonic models. 

Fig. 1 Topography of the coasts and floor of the Black Sea. Bottom relief 1 shelf a accumulative, b abrasive 2 continental slope a accumulative, b stepwise 3 floor of the basin 4 continental footstep 5 underwater canyons 6 bars a sandy, b marginal 7 morphological boundaries a distinct, b fuzzy. Coast types 1 landslide 2 abrasive 3 abrasive-accumulative 4 accumulative 5 lagoonal 6 deltaic...

For example, these kinds of processes actively proceed on the Caucasian continental slope off Dzhugba and Arkhipo-Osipovka. Here, the underwater relief is characterized by extreme complicacy and irregularity. Landslide formations are encountered at depths of about 850 m at a distance of 6 km from the coast. The thickness of the sliding units is 20-25 m at a length of 350-400 m. The landslides descend to depths of 1200-1500 m at the foot of the continental slope. 

Lidmar-Bergstrom, K., Olsson, S. Roaldset, E. (1999) Relief features and pala-eoweathering remnants in formerly glaciated Scandinavian basement areas. In Thiry, M. Simon-Coinfon, R. (Eds) Palaeoweathering, Palaeosurfaces and Related Continental Deposits. Special Publication 27, International Association of Sedimentologists. Oxford Blackwell Science, pp. 275-301. 

About 80 per cent of ROK are in regions where the altitude of the summit ranges from 300 to more than 1,000 meters. The land bears a strongly dissected relief reworked by numerous erosion cycles. The low lands include both coastal plains clayey materials and the continental alluvial plains and valley flood plans of the interior. 

Physical-geographical conditions combination of steppe and forest-steppe. The climate is temperate continental in winter the mean monthly air temperature is about 10 degrees below zero, in summer it is about 20 degrees above zero. Snow cover is extensive and reaches 30 -50 cm. The relief is partially plane, partially covered with hills. The highest points are about 800 - 900 m above the sea level. The average duration of positive temperature period comprises 200 - 250 days a year. 

The process of physical erosion of elevated terrains and subsequent transport and deposition of the eroded material downstream or downwind from the source are shown schematically in Figure 4. While erosion of the land relief and transport of the eroded materials by rivers are essentially continuous processes driven by the uplift of the continental surface, considerable uncertainties exist in... 

The existence of positive relief features and mountains is an almost self-explanatory indication that the rates of uplift of some continental sections have been much higher than the rates of denudation (Fig. 2). The rates of erosion that about balance or are slightly below the rates of uplift characterize the stable shield areas of South America, 10-20 mm ka and a tectonically active island Formosa (Taiwan), where uplift rates are as high as 103-104 mmka-1 (Stallard, 1988). 

Mean elevation of the continents is 840 m (Lagrula, 1965 Sverdrup et al., 1942 Gates and Nelson, 1975). A modest mountain relief of 2000-2500 m occupies about 5% of the unglaciated continental area (Fig. 4B), and its linear rate of erosion is, from Eq. 7... 

Pinet, P., and M. Sourian (1988), Continental Erosion and Large Scale Relief, Tectonics 7 (3), 563-582. 

Since the downwarping of the continental margin did not require uplift inland of the Fall Line, erosion rates on much of the land surface supplying sediment to the continental margin must have remained relatively low. Menard (1961) estimated that 7.8 x 10 km of rock must have been removed from the Appalachians over 125 Myr to account for the sediment now on the continental terrace and rise and on the abyssal plains off the east coast of North America. The mean sediment yield required to produce this material is —0.2 kg/(m yr). (For comparison, this is about the same as the sediment yield of the Missouri River drainage basin today.) Matthews (1975) has used the more extensive data on sediment thicknesses off the Atlantic Coast now available to estimate that the sediment yield of eastern North America over the past 60 Myr was 0.012 kg/(m yr) for the northern half of the coast and 0.067 for the southern half. These sediment yields can be attained with a land surface relief of a few hundred meters under temperate climate conditions and so are consistent with the hypothesis that both the elevation and relief of most of the land surface have remained moderate since the opening of the Atlantic Ocean. 

Within subsiding continental basins, groundwater can be induced by sediment compaction (pressure water) and by driving forces from topographic relief or from variations in fluid density. The intensive water flow can disturb the thermal profile and change the time-temperature history of buried source rocks. Maximal rate of pressure-water expulsion (Rpwe) can be estimated relatively easily using Eqs. 6.i and 6.2 for the case of one-dimensional consolidation of homogeneous sediments on immobile basement ... 

Bathymetric shaded relief map showing extent of continental margins. (Courtesy of National Geophysical Data Center, http //www.ngdc.noaa.gov/mgg/global/global.html.)... 

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