Flank collapse at Mount Wrangell, Alaska, recorded by volcanic mass-flow deposits in the Copper River lowland

2002 ◽  
Vol 39 (8) ◽  
pp. 1257-1279 ◽  
Author(s):  
Christopher F Waythomas ◽  
Kristi L Wallace
Keyword(s):  
Debris Flow ◽  
Mass Flow ◽  
Volcanic Rocks ◽  
Debris Avalanche ◽  
Sector Collapse ◽  
Flow Forming ◽  
Flank Collapse ◽  
South Central ◽  
Flow Deposit ◽  
Facies Types

An areally extensive volcanic mass-flow deposit of Pleistocene age, known as the Chetaslina volcanic mass-flow deposit, is a prominent and visually striking deposit in the southeastern Copper River lowland of south-central Alaska. The mass-flow deposit consists of a diverse mixture of colorful, variably altered volcanic rocks, lahar deposits, glaciolacustrine diamicton, and till that record a major flank collapse on the southwest flank of Mount Wrangell. The deposit is well exposed near its presumed source, and thick, continuous, stratigraphic exposures have permitted us to study its sedimentary characteristics as a means of better understanding the origin, significance, and evolution of the deposit. Deposits of the Chetaslina volcanic mass flow in the Chetaslina River drainage are primary debris-avalanche deposits and consist of two principal facies types, a near-source block facies and a distal mixed facies. The block facies is composed entirely of block-supported, shattered and fractured blocks with individual blocks up to 40 m in diameter. The mixed facies consists of block-sized particles in a matrix of poorly sorted rock rubble, sand, and silt generated by the comminution of larger blocks. Deposits of the Chetaslina volcanic mass flow exposed along the Copper, Tonsina, and Chitina rivers are debris-flow deposits that evolved from the debris-avalanche component of the flow and from erosion and entrainment of local glacial and glaciolacustrine diamicton in the Copper River lowland. The debris-flow deposits were probably generated through mixing of the distal debris avalanche with the ancestral Copper River, or through breaching of a debris-avalanche dam across the ancestral river. The distribution of facies types and major-element chemistry of clasts in the deposit indicate that its source was an ancestral volcanic edifice, informally known as the Chetaslina vent, on the southwest side of Mount Wrangell. A major sector collapse of the Chetaslina vent initiated the Chetaslina volcanic mass flow forming a debris avalanche of about 4 km3 that subsequently transformed to a debris flow of unknown volume.

scholarly journals Stratigraphy, facies architecture and emplacement history of the c. 3.6 ka B.P. Ngatoro Formation on the eastern flanks of Egmont Volcano, western North Island, New Zealand

2021 ◽  
Author(s):  
◽  
Benjamin John Dixon
Keyword(s):  
New Zealand ◽  
Debris Flow ◽  
Mass Flow ◽  
Extended Phase ◽  
Facies Architecture ◽  
Eruptive Event ◽  
Central Java ◽  
Flow Deposit ◽  
History Of ◽  
Mass Flows

<p>The Ngatoro Formation is an extensive volcaniclastic deposit distributed on the eastern lower flanks of Egmont Volcano, central North Island, New Zealand. Formally identified by Neall (1979) this deposit was initially attributed to an Egmont sourced water-supported mass flow event c. 3, 600 ¹⁴C years B.P. The Ngatoro Formation was subsequently described by Alloway (1989) as a single debris flow deposit closely associated with the deposition of the underlying Inglewood Tephra (c. 3,600 ¹⁴C yrs B.P) that had laterally transformed into a hyperconcentrated- to- flood flow deposit. Such water-supported mass flows have been well documented on volcanoes both within New Zealand (i.e. Mt Ruapehu) and elsewhere around the world (i.e. Mt Merapi, Central Java and Mt St Helens, Washington). This thesis comprises field mapping, stratigraphic descriptions, field and laboratory grain size and shape analysis, tephrochronology and palaeomagnetic analysis with the aim of refining the stratigraphy, facies architecture and emplacement history of the c. 3,600 ¹⁴C yrs B.P. Ngatoro Formation.  This study has found that the Ngatoro Formation has a highly variable and complex emplacement history as evidenced by the rapid textural changes with increasing distance from the modern day Egmont summit. The Ngatoro Formation comprises two closely spaced mass flow events whose flow and emplacement characteristics have undergone both proximal to distal and axial to marginal transformations. On surfaces adjacent to the Manganui Valley on the deeply incised flanks of Egmont Volcano, the Ngatoro Formation is identified as overbank surge deposits whereas at the boundary of Egmont National Park it occurs as massive, pebble- to boulder-rich debris flow deposits. At intermediate to distal distances (17-23 km from the modern Egmont summit) the Ngatoro Formation occurs as a sequence of multiple coalescing dominantly sandy textured hyperconcentrated flow deposits. The lateral and longitudinal textural variability in the Ngatoro Formation reflects downstream transformation from gas-supported block-and-ash flows to water-supported debris flows, then subsequently to turbulent pebbly-sand dominated hyperconcentrated flows.  Palaeomagnetic temperature estimates for the Ngatoro Formation at two sites (Vickers and Surrey Road Quarries, c. 10 km from the present day Egmont summit) indicate clast incorporation temperatures of c. 300°C and emplacement temperatures of c. 200°C. The elevated emplacement temperatures supported by the Ngatoro Formation’s coarse textured, monolithologic componentry suggest non-cohesive emplacement of block-and-ash flow debris generated by the sequential gravitational collapse of an effusive lava dome after the paroxysmal Inglewood eruptive event (c. 3,600 ¹⁴C yrs B.P.). The occurrence of a prominent intervening paleosol between these two events suggest that they are not part of the same eruptive phase but rather, the latter is a product of a previously unrecognised extended phase of the Inglewood eruptive event. This study recognises the potential for gravitational dome collapse, the generation of block-and-ash flows and their lateral transformation to water-support mass flows (debris, hyperconcentrated and stream flows) occurring in years to decades following from the main eruptive phase. This insight has implications with respect to the evaluation of post-eruptive hazards and risk.</p>

scholarly journals Stratigraphy, facies architecture and emplacement history of the c. 3.6 ka B.P. Ngatoro Formation on the eastern flanks of Egmont Volcano, western North Island, New Zealand

2021 ◽  
Author(s):  
◽  
Benjamin John Dixon
Keyword(s):  
New Zealand ◽  
Debris Flow ◽  
Mass Flow ◽  
Extended Phase ◽  
Facies Architecture ◽  
Eruptive Event ◽  
Central Java ◽  
Flow Deposit ◽  
History Of ◽  
Mass Flows

<p>The Ngatoro Formation is an extensive volcaniclastic deposit distributed on the eastern lower flanks of Egmont Volcano, central North Island, New Zealand. Formally identified by Neall (1979) this deposit was initially attributed to an Egmont sourced water-supported mass flow event c. 3, 600 ¹⁴C years B.P. The Ngatoro Formation was subsequently described by Alloway (1989) as a single debris flow deposit closely associated with the deposition of the underlying Inglewood Tephra (c. 3,600 ¹⁴C yrs B.P) that had laterally transformed into a hyperconcentrated- to- flood flow deposit. Such water-supported mass flows have been well documented on volcanoes both within New Zealand (i.e. Mt Ruapehu) and elsewhere around the world (i.e. Mt Merapi, Central Java and Mt St Helens, Washington). This thesis comprises field mapping, stratigraphic descriptions, field and laboratory grain size and shape analysis, tephrochronology and palaeomagnetic analysis with the aim of refining the stratigraphy, facies architecture and emplacement history of the c. 3,600 ¹⁴C yrs B.P. Ngatoro Formation.  This study has found that the Ngatoro Formation has a highly variable and complex emplacement history as evidenced by the rapid textural changes with increasing distance from the modern day Egmont summit. The Ngatoro Formation comprises two closely spaced mass flow events whose flow and emplacement characteristics have undergone both proximal to distal and axial to marginal transformations. On surfaces adjacent to the Manganui Valley on the deeply incised flanks of Egmont Volcano, the Ngatoro Formation is identified as overbank surge deposits whereas at the boundary of Egmont National Park it occurs as massive, pebble- to boulder-rich debris flow deposits. At intermediate to distal distances (17-23 km from the modern Egmont summit) the Ngatoro Formation occurs as a sequence of multiple coalescing dominantly sandy textured hyperconcentrated flow deposits. The lateral and longitudinal textural variability in the Ngatoro Formation reflects downstream transformation from gas-supported block-and-ash flows to water-supported debris flows, then subsequently to turbulent pebbly-sand dominated hyperconcentrated flows.  Palaeomagnetic temperature estimates for the Ngatoro Formation at two sites (Vickers and Surrey Road Quarries, c. 10 km from the present day Egmont summit) indicate clast incorporation temperatures of c. 300°C and emplacement temperatures of c. 200°C. The elevated emplacement temperatures supported by the Ngatoro Formation’s coarse textured, monolithologic componentry suggest non-cohesive emplacement of block-and-ash flow debris generated by the sequential gravitational collapse of an effusive lava dome after the paroxysmal Inglewood eruptive event (c. 3,600 ¹⁴C yrs B.P.). The occurrence of a prominent intervening paleosol between these two events suggest that they are not part of the same eruptive phase but rather, the latter is a product of a previously unrecognised extended phase of the Inglewood eruptive event. This study recognises the potential for gravitational dome collapse, the generation of block-and-ash flows and their lateral transformation to water-support mass flows (debris, hyperconcentrated and stream flows) occurring in years to decades following from the main eruptive phase. This insight has implications with respect to the evaluation of post-eruptive hazards and risk.</p>

The cohesive Naranjo debris-flow deposit (10 km3):

2002 ◽  
Vol 117 (1-2) ◽  
pp. 213-235 ◽  
Author(s):  
L Capra ◽  
J.L Macı́as
Keyword(s):  
Debris Flow ◽  
Debris Flow Deposit ◽  
Flow Deposit

scholarly journals Morphological analysis of hummocks in debris avalanche deposits around Mt Erciyes, central Turkey

2017 ◽  
Author(s):  
Yuichi S. Hayakawa ◽  
Hidetsugu Yoshida ◽  
Hiroyuki Obanawa ◽  
Ryutaro Naruhashi ◽  
Koji Okumura ◽  
...  
Keyword(s):  
Cross Sections ◽  
Flow Direction ◽  
Debris Avalanche ◽  
Caldera Wall ◽  
High Definition ◽  
Sector Collapse ◽  
Initial Flow ◽  
The North ◽  
Aircraft System ◽  
Central Turkey

Abstract. Debris avalanche caused by the sector collapse of a volcanic mountain often forms characteristic depositional landforms including hummocks. Not only sedimentological but also geomorphological analyses of debris avalanche deposits (DAD) are crucial to clarify the size, mechanisms, and processes of the debris avalanche. We investigate the morphology of hummocks newly identified in the DAD at the north-eastern flank of Mt. Erciyes in Kayseri, central Turkey, likely formed in the late Pleistocene. Using a remotely piloted aircraft system (RPAS) and the structure-from-motion multi-view stereo photogrammetry (SfM), we obtained high-definition digital elevation model (DEM) and orthorectified image of the DAD surface with hummocks. Detailed geometric features of the hummocks are investigated using the RPAS-derived high-definition DEM. The source volume of the DAD was also estimated by reconstructing the original shape of the mountain body using a lower-resolution satellite-based DEM. For this, topographic cross sections are examined based on the slopes around the scar that are regarded as the remnant topography preserved since the sector collapse. The spatial distribution of hummocks shows an unusual pattern regarding the distance-size relationships, i.e., anomalously concentrated in a certain distance from the source. The hummocks are found to be aligned toward the flow direction of the debris avalanche, suggesting the extensional regime of the debris avalanche. These facts indicate that this debris avalanche did not follow the typical flow type of debris avalanches observed in the other cases. Instead, the topographic constraints by former caldera wall and fault-induced lineaments could have strongly affected the flow course and pattern in this particular case: The pre-existing caldera wall topography could have acted as the topographic barriers for the debris avalanche to force the initial flow to turn northward, and the flow regime to be once compressional followed by extensional at the narrow and steepened outlet valley. Also, the estimated volume of the DAD 12–15 × 108 m3 gives its mean thickness of 60–75 m, which is much deeper than the reported cases of other DADs. This suggests that the debris avalanche could have flown down to the far downstream areas from the presently-observed limit of the DAD extent. Assessments of the DAD including the results of this study can provide further insights into the risk and mitigation of potential disasters in the study area.

Dosage du potassium, de l'uranium, du radium et du thorium, par spectrometrie gamma dans les laves d'Auvergne, du Velay et de la province sicilienne

1963 ◽  
Vol S7-V (2) ◽  
pp. 218-231 ◽  
Author(s):  
Jean Louis Cheminee ◽  
Daniel Nordemann
Keyword(s):  
Hydrothermal Alteration ◽  
Volcanic Rocks ◽  
Statistical Dependence ◽  
Direct Proportion ◽  
Radioactive Elements ◽  
Spectrometry Analysis ◽  
Functional Relations ◽  
South Central ◽  
Intrusive Rocks ◽  
Radioactive Minerals

Abstract Fifty samples of volcanic rocks from south-central France, ranging from basalts to rhyolites, were subjected to gamma spectrometry analysis for the purpose of determining the proportions and relationships of the constituent radioactive elements. Zircon, sphene and apatite generally contained less thorium and uranium than the less abundant accessory minerals such as allanite, monazite and xenotime. Results of the analysis also show that the percentage of radioactive minerals is greater in the acidic lavas than in the intrusive rocks, suggesting that the latter were subjected to hydrothermal alteration. The percentage of potassium varies in direct proportion to the variation in the percentage of silica. The increase in thorium as a function of silica is more rapid than that of uranium. Graphically, no correlation exists between the percentage of radium and silica. The concentrations of uranium and thorium do not vary independently but seem to have a statistical dependence whose functional relations are not yet apparent.

Evolution of the south-central segment of the Archean Abitibi Belt, Quebec. Part II: Tectonic evolution and geomechanical model

1983 ◽  
Vol 20 (9) ◽  
pp. 1355-1373 ◽  
Author(s):  
Erich Dimroth ◽  
Lazlo Imreh ◽  
Normand Goulet ◽  
Michel Rocheleau
Keyword(s):  
Tectonic Evolution ◽  
Anisotropic Plate ◽  
Volcanic Rocks ◽  
Sedimentary Rocks ◽  
Normal Fault ◽  
Geomechanical Model ◽  
Southwestern Part ◽  
South Central ◽  
Central Segment ◽  
Volcanic Terrain

In this paper, we describe the relations between the paleogeographic and tectonic evolution of the southwestern part of the Archean Abitibi and Bellecombe belts. Volcanism in the Abitibi Belt created a very thick, anisotropic plate composed of competent volcanic rocks and broken by the Duparquet–Destor break. The depocenters of the upper division of diverse volcanic rocks subsided about 10 km relative to their surroundings, and some central volcanic complexes within this division were consolidated by synvolcanic plutons and their thermal metamorphic aureole. The Cadillac break, a normal fault, separated the Abitibi and Bellecombe belts. The latter consisted of comparatively incompetent sedimentary rocks on top of a basement composed of ultramafic–mafic flows.North–south compression of the volcanic terrain during the Kenoran Orogeny produced a set of flexure folds, F1, that curve around the consolidated cores of central volcanic complexes generally in an easterly direction. Synclinoria nucleated at the deeply subsident depocenters of the upper diverse division. Further north–south flattening and subvertical stretching produced the east-trending F2 folds, their axial-plane schistosity S2, and local superposed schistosities S3 and S4. Southward verging recumbent folds suggest that the Bellecombe Belt simultaneously was pulled northward below the Abitibi Belt. During the orogeny, the Duparquet–Destor and Cadillac breaks were transformed to thrust faults; the Duparquet–Destor break also shows minor (< 3 km) right-lateral strike slip. Diapiric rise of late- to post-kinematic plutons locally distorted earlier schistosities.

Spectral correlation of magnetic and gravity anomalies of Ohio

Geophysics ◽  
1997 ◽  
Vol 62 (1) ◽  
pp. 365-380 ◽  
Author(s):  
Ralph R. B. von Frese ◽  
Michael B. Jones ◽  
Jeong Woo Kim ◽  
Wen Sheng Li
Keyword(s):  
Volcanic Rocks ◽  
Gravity Anomalies ◽  
Field Analysis ◽  
Positive Density ◽  
Upper Crust ◽  
Spectral Correlation ◽  
South Central ◽  
Basement Rocks ◽  
Positive Correlations ◽  
First Vertical Derivative

Geologic interpretation of Ohio's magnetic or gravity anomalies is hindered by the effects of anomaly superposition and source ambiguity inherent to potential field analysis. A common approach to minimizing interpretational ambiguities is to consider analyses of anomaly correlations. A spectral procedure is adapted which correlates anomaly fields in the frequency domain to produce filters separating positively and negatively correlated, as well as null correlated features. The correlation filter passes or rejects wavenumbers between coregistered fields based on the correlation coefficient between common wavenumbers as given by the cosine of their phase difference. This procedure is applied to reduced‐to‐pole magnetic and first vertical derivative gravity anomalies of Ohio for mapping correlative magnetization and density contrasts within the basement rocks. The analysis reveals predominantly positive correlations between anomaly maxima and minima. Correlative anomaly maxima may be generally modeled as mafic bodies of the upper crust. They map out a possible dike complex in northwestern Ohio, a batholith as a possible source of volcanic rocks in southwestern Ohio, and numerous mafic bodies related presumably to Keweenawan rifting and Grenville tectonics. Correlative anomaly minima include several isolated features that may define felsic terranes of the upper crust, and ringed features around some of the larger mafic bodies which also may contain significant edge‐effect components. A large circular feature in south‐central Ohio involves correlative minima of a possible anorthosite body that is ringed by an inversely correlative zone of positive density and negative magnetization contrasts. Another prominent negative correlation involves an extensive area of possible extrusive rocks with positive magnetization and negative density contrasts just north of the batholith in southwestern Ohio.

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