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Structure and landforms
Published in Richard J. Chorley, Stanley A. Schumm, David E. Sugden, Geomorphology, 2019
Richard J. Chorley, Stanley A. Schumm, David E. Sugden
The retreat of the edges of horizontal sedimentary sequences produce, first, terraces and structural benches, such as the Tonto Platform (due to stripping back to Tonto Shales) and the Esplanade (supported by the Redwall Limestone) in the Grand Canyon, and then widening stripped and structural plains (Figure 7.2) which may be dotted with isolated residuals of larger (mesa – Spanish, ‘table’) or smaller (butte, from butt of a tree) size. Such residuals or outliers occur, albeit in a less stark form, in humid regions, such as Brent Knoll, Somerset, and Bredon Hill, Worcestershire. Some of these structural surfaces are very extensive, for example, covering thousands of square kilometres in Southern Africa, and it is a matter of current dispute as to whether this scale of structurally controlled stripping is possible of accomplishment at elevations well above sea level (see subject of pediplains, Section 2.4.2). Three examples of structural surfaces are the Edwards Plateau of Texas supported by the Edwards Limestone (about 300–1000 m above sea level and 130–400 m above the surrounding countryside); Salisbury Plain, England, supported by the flinty and permeable Echinoid Chalk from which the Belemnite Chalk has been stripped; and the summit levels of the Appalachian Plateaus (650–750 m; 2000–2250 ft) supported by the Pottsville and Pocono Sandstones which have been dissected into a hierarchy of regular drainage basins of 300–700 m (1000–2000 ft) relief (see Chapter 13.2).
Landslides in the Transantarctic Mountains: lower Jurassic and older strata displaced in late Mesozoic to late Cenozoic time
Published in New Zealand Journal of Geology and Geophysics, 2022
The proposal by Lisker and Laufer (2013) of an up to 4-km-thick Mesozoic sedimentary cover leads to a somewhat different interpretation. That cover necessitates a low-lying terrain crossed by rivers transporting debris from one or more elevated terrains, the most probable and proximal one being the sub-glacial Gamburtsev Mountains of possible early Paleozoic origin (Veevers 2018). Cretaceous secondary mineralisation events may have been related to the burial of the Beacon and Ferrar rocks rather than groundwater changes due to slow uplift. Further, the Mesozoic beds, which must have been at most weakly consolidated and therefore easily eroded, had to have been removed no later than during the early Eocene on the initiation of rapid uplift. The mesa and butte topography, therefore, must post-date removal of the Mesozoic beds, which then dictates that it was developed no later than in Early Eocene time.
Automated location correction and spot height generation for named summits in the coterminous United States
Published in International Journal of Digital Earth, 2020
Samantha T. Arundel, Gaurav Sinha
One GNIS summit point, Lone Butte, Nevada (NV) (Nye County), was found on a plain, but near several eminences, and not labeled on the topographic map in the HTMC for verification (Figure 6). Whereas the GNIS point was closest to the small feature marked by a 6641-foot (ft) spot elevation, that eminence was not uphill from the point, and neither was the nearby feature marked by a 6980-ft spot elevation. Instead, stepping upslope brought the point to a larger eminence farther away to the southeast (indicated by the blue triangle). From all information available, it was impossible to know which eminence was indicated by the position of the GNIS summit point. Currently, there is no way to automate a correction for these types of points, of which there were three (1.5%), so these points were removed from further statistical analyses.
Hydrological perturbations drive rapid shifts in phytoplankton biodiversity and population dynamics in Butte Lake (Lassen Volcanic National Park, California)
Published in Lake and Reservoir Management, 2018
The morphometry for Butte Lake and its catchment is reported in Table 1. Although Butte Lake has a modest surface area of ∼1 km2, it is one of the largest lakes in LAVO. The lake has limited shoreline development (3.8; Fig. 1Table 2, shaped like a very jagged letter “L”) and a high drainage ratio (135). In fact, the Butte Lake watershed is one of the largest catchment areas (∼114 km2) in LAVO, covering just over 16% of the park area (Fig. 3a). Butte Lake is geographically and elevation-wise the last stop for surface water flowing from LAVO headwater areas eastward along the Cascade divide. Four major sub-catchment areas were identified, arbitrarily designated as the Fantastic Lava Beds (4.3 km2), Widow (14.8 km2), Cinder Cone (7.2 km2), and Snag (87.4 km2) sub-catchments based on proximity to named park features (Fig. 3a). It is unlikely that the entire Butte Lake watershed area consistently serves as the effective size of the catchment for water that enters Butte Lake. There are a number of other lakes within the catchment area (i.e., Widow Lake or Snag Lake; Fig. 3a) that are “sinks” for water entering parts of the catchment, and surface water outflow from these systems may only make it to Butte Lake in years with above-average precipitation, resulting in a large volume of surface water flow and groundwater recharge. Butte Creek (Fig. 1) is the outflow point for the whole system even though parts of the Butte Lake catchment may sometimes be disconnected in terms of surface water drainage. Water that makes it to Snag Lake flows as groundwater to Butte Lake through the Fantastic Lava Beds (Clynne et al. 2000), but the effective size of the Snag Lake catchment is also variable, and outflow from lakes in its upper watershed may also diminish during periods of below-average precipitation. In dry years, Butte Lake functions like a closed, endorheic or terminal lake system, with water entering the lake leaving mainly through evaporation or groundwater flow.