Geomorphological Patterns Research Articles

Pluviometric pattern of the Island of Sardinia with regard to extreme precipitations related to meteorological and climatological conditions

The pluviometric characteristics of Sardinia are given by the analysis of the island’s geomorphological pattern and of the various types of weather mostly affecting such Mediterranean area during autumn and winter seasons.

A new technique for recognition of geological and geomorphological patterns in digital terrain models

We have developed a technique that recognizes monoclinal sedimentary strata showing strike ridge geomorphology and fluvial deposits from Digital Terrain Models (DTMs). This technique is efficient and reliable and may be expanded to analysis of other landforms. Techniques for rapid geomorphic analysis of DTMs are becoming increasingly useful since digital stereoscopic SPOT data will soon be available worldwide. Our technique recognizes geomorphic elements in two steps. First, elementary objects including crests, thalwegs, and various slope types are classified from slope changes along N - S, E - W, NW - SE, and NE- SW profiles through pixels in the DTM image. Second, grammatical pattern recognition is used to identify and map geomorphic forms from the succession of elementary objects.

NEW VIEWS ON MORPHOSTRUCTURE OF MARGINAL SEAS OF EASTERN ASIA

Marginal seas of Eastern Asia which form a transition zone from the continent to the Pacific are considered from new positions: as a system of gigantic morpho-structures of the central type (mega-MCT). The main features of geological and geomorphological patterns and evolution of megastructures in question have been identified. The formation of the recent geomorphological image of marginal mega-MCT occurred in Mesozoic (mainly in Late Mesozoic)-Cenozoic under the conditions of continuous extension of the earth's crust over the whole western Pacific margin.

The seismicity, geomorphology and structural evolution of the Corinth area of Greece

In the eastern Gulf of Corinth, geological structure is closely reflected in the topography. In the 1981 Corinth earthquakes ground deformation accentuated existing geomorphological patterns. We explore the relationship between seismicity and landforms in space and time. The area examined extends beyond the epicentral region of the 1981 events and its evolution is traced over the last 40000 years. To understand the relation between deep and superficial structures we discuss processes that occurred in the 1981 earthquakes, and go on to propose that surface faulting appears only above linear faults at depth that move in earthquakes with magnitudes ( M s ) greater than six. Where faults at depth intersect or bend, the faulting becomes distributed and prim ary faulting does not reach the surface. Here the surface manifestation of faulting at depth is surface folding and secondary faulting. Such regions are identified in maps of the eastern Gulf of Corinth. Evidence for the evolution of the fault systems is provided by eyewitness accounts of shoreline changes following the recent earthquakes, historical and archaeological data pertaining to old sea levels, and 14 C dates for molluscs collected from fossil shorelines. The results of these studies broadly confirm an earlier view of J. A. Jackson et al . ( Earth planet. Sci. Lett . 57, 377—397 (1982)) that motion has shifted from faulting south of the city of Corinth to faulting in the Perachora peninsula. But the transfer is not complete: areas lying between the two fault systems have moved up and down in historical and archaeological times indicating that both systems are still active. The evidence for activity of the northern system points to a repeat time of 300 years for earthquakes com parable with those of 1981. The work discussed in this paper suggests that some of the features previously described as m arine terraces are fault-controlled continental surfaces. Furtherm ore, beach deposits at a num ber of different levels long regarded as successive shorelines are in fact contemporaneous. The critical ages were obtained by radiocarbon dating of shell carbonate, a technique which yields dependable results if applied to samples which have been carefully selected and pretreated. Palaeontological dating of the terraces, in contrast, is found to be misleading because the faunas are environm entally controlled and consequently diachronous.

A propos de quelques formes fluviales de la vallée du Haut-Rhône français

A study of two reaches of the French Upper Rhône marks out several geomorphological patterns with minor forms, each having its own dynamic evolution. The speed of renewal and disappearance of these units explains the dynamic evolution of the biocoenoses linked to these environments. The reserves set up along the rivers must allow the rejuvenation of fluvial land forms.

Erosion Below Main Stem Dams on the Missouri River

Six dams were constructed on the main stem of the Missouri River between 1937 and 1963. The dams, built and maintained by the U.S. Army Corps of Engineers, include Fort Peck, Garrison, Oahe, Big Bend, Fort Randall, and Gavins Point. The “Big Muddy,” a nickname derived from the Missouri9s tremendous silt load, has been transformed into a chain of lakes through most of South Dakota and North Dakota, and much of Montana. Below Gavins Point, the lowermost dam, the Missouri River begins anew as a sediment-free stream, and the water immediately starts to derive a new load, primarily from lateral erosion of the river banks. Normal summer water releases from Gavins Point since 1953 have been about 32,000 cubic feet per second (900 cubic meters per second), but releases during the summer of 1975 were about 60,000 cfs (1,700 cms) because of high runoff from headwater areas. This increased discharge caused severe erosion and hundreds of acres of adjacent farm and forest land sloughed into the stream during 1975. While the Corps of Engineers assumes no responsibility to riparian landowners for this erosion, it has provided $94,000 to prevent the erosion of the Sacred Heart Hospital at Yankton, South Dakota. Inspection of aerial photographs and space imagery taken during 1953, 1973, and 1976 indicates the areas where erosion is active within a 55 mile (88 km) reach studied below Gavins Point dam. In general, the geomorphological pattern of erosion and deposition on alternate sides of a meander bend has been replaced by active erosion along all sides of the river, creating an ever-widening, shallow, braided stream.

An Outline of the Zoogeography of the Levant1

AbstractPor, F. D. (Department of Zoology, The Hebrew University of Jerusalem, Jerusalem, Israel.) An outline of the zoogeography of the Levant. Zool. Scr. 4 (1): 5–20, 1975.–The marine, freshwater and terrestrial distributional patterns in the region of the Eastern Mediterranean shorelands are discussed. Several historical formative events are singled out and especially the desertification of what is called the Palaeo‐eremic region. Thus a subtraction‐transition area between the Palae‐arctic and Ethiopian regions appeared. Faunal elements belonging to these three regions can be found in the area, admixed with a few Orienta species. The distributional pattern of the marine fauna is dominated by the faunal invasion from the Indo‐Westpacific region to the Mediterranean. The distribution of the freshwater animals more or less follows that of the terrestrial fauna with the important exception of the Oriental and Ethiopian fishes which took advantage of the steeplechase waterways leading from the Euphrates into the rivers of the Rift Valley. The humid tropical oasis enclaves as well as many of the freshwaters are the specific environments where most of the zoogeographically interesting species and endemics are found. These are precisely the environments which have most suffered from human interference.Summary(1) The Levant province is a meeting place and transitional area between the Palaearctic, Oriental and Ethiopian zoogeographic regions. In the marine world, its coasts are inhabited by the temperate Atlantic‐Mediterranean fauna and the tropical Indo‐Pacific fauna.(2) The broad “Palaeo‐eremic” desert belt serves as a filtering barrier between the three faunal regions. Inhabited by a peculiar fauna of mixed origin, the Palaeo‐eremic belt does not belong to any of the above‐mentioned regions. The ability to cross the desert barrier differs for the different taxa: it is maximal for mammals, birds and insects. Freshwater fish use a peculiar “steeple chase” waterway connecting the Nile with the Euphrates through the waterways of the Rift valley. The man‐made Suez Canal serves as a filtering pathway through which the Indo‐Pacific tropical fauna invades the Mediterranean.(3) In the terrestrial environments, the transition from the dominance of the Palae‐arctic species in the north to that of the Palaeo‐eremic species in the south, is complicated by the fourfold longitudinal geomorphological pattern of the area. Palae‐arctic species advance south along the cis‐ and trans‐rift mountain ranges, while Palaeo‐eremic and Ethiopian species extend northwards along the coastal plain and the Rift valley. The Indo‐Pacific emigrants to the Mediterranean advance northwards along the Levant coast, and their influence gradually decreases towards the north.(4) The Levant province has suffered the most profound human impact for some 10 000 years. Nevertheless, there are some endemic species in the area. These are animals of Palaeo‐eremic or Ethiopian character, especially concentrated in the waters and oases of the Rift valley. The wealth of the marginal populations in the zoogeographic, ecological, and physiological sense, makes protection of species and habitats especially important.

Dynamic models of geomorphological patterns

A deformation mechanism is described and analyzed. It is intended for height patterns exposed to erosion and tectonic activity. A simulation experiment is carried out for this model. Closedform expressions are derived for the covariance field, the properties of spectral estimates, and for the optimal retrospective reconstruction of earlier, unknown height patterns. For obvious reasons the author is in no position to make claims about the verisimilitude of the model. It is offered as an example of a potential application to geology of the theory of patterns developed by the author and his coworkers in recent years. It is hoped that those more qualified than the author in the subject matter area can extend and modify the analysis to make it closer to geological reality.