Opera Corcontica: Detail článku

Úvodní strana

Profil časopisu

Redakční rada

Archiv ročníků

Publikační etika a politika

Pokyny pro autory

Úvodní strana > Archiv ročníků > Články > Zobrazení článku

Detail článku

Ročník:

56/2019

Název česky:

Role říčních pirátství při vývoji reliéfu Krkonoš

Název anglicky:

The role of the stream capture in the Krkonoše Mts geomorphological development

Autor (autoři):

Vlastimil Pilous

Klíčová slova česky:

saxonská tektonika, morfotektonika, pasivní morfostruktura, erozní reliéf, vývoj a změny říční sítě, říční pirátství

Klíčová slova anglicky:

Saxon tectonics, morphotectonics, passive morphostructure, erosion surface, development and changes of river network, stream and river capture

Od strany:

163

Do strany:

182

Abstrakt česky:

Krkonoším je jako nejvyššímu českému pohoří již dlouhodobě věnována pozornost geomorfologů, ale
téměř výhradně se zaměřuje na kvartérní problematiku. Základní reliéfové prvky a znaky pohoří, stejně jako celková
orografi cká situace se však formovaly již podstatně dříve, jako následek největšího tektonického zdvihu pohoří v oligocénu
a miocénu. Intenzivní nástup zpětné a hloubkové eroze provázející tento zdvih byl na české straně pohoří, tj.
v geologicky pestrém území, velmi silně ovlivněný a směrovaný lokálními tektonickými (poruchová pásma) a zvláště
pasivně strukturními poměry. Mimořádně významně se v tomto směru uplatnil kontaktní dvůr a uvnitř krystalinika
pásmo ortorul, které se obloukovitě táhne od Žalého na západě až k Pomezním Boudám na severovýchodě. Právě
u něj lze předpokládat, že zapříčinil dvě nejvýznamnější říční pirátství na české straně Krkonoš a zásadní změnu
v odvodňování východní části Krkonoš. S ohledem na neogenní stáří těchto procesů však chybí přímé důkazy těchto
změn, neboť erozně denudační snížení reliéfu, které od té doby proběhlo, představuje na území zarovnaných povrchů
řádově desítky metrů a v prostoru erozních údolí dokonce stovky metrů. To vylučuje možnost zachování jakýchkoliv
terciérních sedimentů, a proto lze vycházet pouze z vyhodnocení sklonových a morfostrukturních poměrů.

Abstrakt anglicky:

The Krkonoše Mts (the Giant Mts) are the highest Czech mountain range, thus it has gained the attention
of geomorphologists for a long time, but with a focus almost exclusively on Quaternary issues. However, the
basic geomorphological elements and features of the mountains, as well as the overall orographic situation, were
formed much earlier, with the largest tectonic uplift of the mountains occurring in the Oligocene and Miocene. Subsequent
intensive onset of headward and downward erosion in a geologically diverse area of the Czech side of the
mountain range was strongly infl uenced both by local tectonic conditions (fault zones) and structural conditions.
The hard rocks of the granite pluton contact zone and the crystalline orthogneiss belt, which extends from the Žalý
Mt in the west to Pomezní Boudy in the northeast, were particularly important in this respect. The presence of the
orthogneiss belt probably caused the two most signifi cant river captures on the Czech side of the Krkonoše Mts
with a fundamental change in the drainage of the eastern part of the mountain range. However, due to the neogenic
age of these processes, there is no direct evidence of these changes. The processes of erosion and denudation since
the Neogene removed tens of meters on the summit planationsurfaces and even hundreds of meters in the valleys.
This excludes the possibility of preserving any tertiary sedimentary deposits, and therefore it makes it only possible
to base the evaluation on the slope and morphostructure surface properties.

Souhrn anglicky:

The Krkonoše Mts are a horst mountain range, rising
signifi cantly above their surroundings, which, after
being uplifted during tertiary Saxon tectonic movements,
gained a signifi cant erosion relief. Changes
in the drainage network, including stream and river
captures, are inherently linked to the development of
erosion relief in the Pliocene and Pleistocene. According
to some assumptions, these occurred also in the
Krkonoše Mts, but due to the absence of old depositional
landforms they are diffi cult to be proved unequivocally.
Thus, we can only study them from indirect
evidence, such as sharp river bends producing
desolate valley sections, or an overall assessment of
the surface in that area, including the morphometric
situation. In some cases it is not clear whether this was
merely a change in fl ow direction, for example due to
slope conditions (for example due to uneven pleistocene
tectonic movements) or seizure in the form of
stream or river capture.
On the steep but mostly geologically uniform Polish
side of the mountain range the river captures originated
entirely by tectonic movements. A subsidiary
linear tectonic depression, known as the Karkonoski
Padól Środgórski, played a crucial role here, with the
largest number of changes in fl ow directions in terms
of their interconnection, at least in some cases in the
form of stream capture. Their existence has been
known for a long time, but detailed geomorphological
assessment according to aerial laser scanning digital
elevation models unequivocally confi rms them.
Cross-border river capture is unique in the area of
the Novosvětské sedlo saddle between the Kamienna
and Milnice rivers, which was the only stream capture
in the Krkonoše Mts that was part of the struggle
for a watershed in the main water divide between the
Odra and Labe river basins. It is realistic to assume
that this was connected with the extremely active tectonic
movements in this area.
On the Czech side of the mountain range, which
is geologically much more diverse, changes in fl ows
in the form of stream or river capture are much more
complicated. Most of them are located on the bedrock
of the Krkonoše Mts crystalline complex and therefore
passively structural causes played a dominant role in
their formation, albeit in some cases also due to local
faults. The only stream capture on the granite bedrock
on the Czech side of the mountain range affected the
Pilský potok brook near Harrachov. It is the youngest,
occurring almost to the Holocene, unlike all others
that occurred in the Pleistocene, or even up to the Pliocene.
Two stream captures, which affected the largest
part of the area of the Czech Krkonoše Mts, were
located in the catchments of the Malé Labe brook and
Úpa river. Both were structurally conditioned by the
presence of a belt of hard muscovite orthogneisses. In
addition, there was the unusual situation othe Malé
Labe brook, where the above-mentioned capture
took place within the same catchment (ie the Malé
Labe brook itself), but there the fl ow was diverted to the neighboring Labe at a lower elevation in the territory
of the Krkonoše Mts foothills.
The second stream capture, which is at the same
time the oldest in the Krkonoše Mts (most likely Pliocene),
was the seizure of the uppermost Úpa river
to the valley lineament of the present-day Malá Úpa
river. This simultaneously occurred from the original
Úpa river fl ow direction to the Čistá brook Basin
and thus the Labe river river in its present form. At
its origin, this stream capture was mostly the result of
passive morphostructural causes in the form of hard
orthogneisses belt, because it also infl uenced the geomorphological
development in the whole wider area
of the Černá hora Mt. The visible impact of this river
capture has been manifested to this day, both in its
immediate vicinity and downstream despite its great
age. In addition to the well-preserved short section
of the past broad valley is preserved on the top of the
Černohorská rozsocha ridge, ie the watershed between
the Úpa and Čistá rivers. A completely atypical, dentritic
drainage pattern originated on both sides. This
residue of the broad valley also contributed signifi -
cantly to the formation of the lowest-elevated glacial
cirque of the Vlčí jáma, as it, together with the adjacent
western slope of Liščí hora Mt. and the atypical diagonal
course of the Černohorská rozsocha, provided
a suffi cient snow defl ation surface for their formation.
In a wider dimension, this stream capture changed
the originally markedly parallel drainage network
of all consequent valleys from the Jizera river to the
Úpa river in the crystalline area of the Czech part of
the Krkonoše Mts by comple transformation into
a dendcritic drainage in the Úpa river catchment.
The accompanying features of this change include
the formation of the only signifi cant subsequent valley
section (the Úpa river bellow Pec pod Sněžkou)
in the crystalline complex, as well as the uniqueobsequent
valleys in the Krkonoše Mts (the Vlčí, Javoří
and Vavřincův potok valleys) and the radial drainage
in the Černá hora Mt. and Světlá hora Mt. massif.
Two previously known small-scale stream captures
are also located in the upper part of the Malá Úpa river
catchment area, which occurred as a result of headward
erosion in a planation surface at a lower elevation.
In this case, the overall slope-aspect situation
of the surface was an important factor, in addition
to the structural and tectonic conditions. Two minor
probable flow direction changes of the Malá Úpa
river are also located in the area of deep-seated valleys
at the confl uence of today's Úpa and Malá Úpa
rivers. However, the complex geological conditions
here do not allow a clear explanation of the cause of
the change in fl ow diredtion.

PDF Download