Growth and decay of palsas and peat plateaus in the Macmillan Pass–Tsichu River area, Northwest Territories, Canada

1979 ◽  
Vol 16 (7) ◽  
pp. 1362-1374 ◽  
Author(s):  
G. P. Kershaw ◽  
Don Gill
Keyword(s):  
Northwest Territories ◽  
Volcanic Ash ◽  
Late Winter ◽  
White River ◽  
The Past ◽  
Ash Fall ◽  
Tall Plant ◽  
Reduction Of Area ◽  
Crustose Lichens ◽  
Peat Plateaus

Macmillan Pass, at 1350 m asl (above sea level), is located in the Selwyn Mountains at the Yukon–Northwest Territories border (63 °15′N, 130°02′W). This area lies within the discontinuous but widespread permafrost zone. Palsa–peat plateau complexes cover 0.7% of the 235 km2 study area and are found in bog and fen depressions at elevations from 1285–1690 m. Palsa heights range from 0.15–9.75 m and diameters from 3.25–75.0 m; peat plateaus have maximum heights of 2.5 m and maximum diameters of 225 m. Both features are vegetated by Cladina-Betula glandulosa, Cladina-Polytrichum-Cetraria, and crustose lichens-Polytrichum plant communities.Palsas and peat plateaus are windswept during winter. On surfaces which support recumbent (5–15 cm tall) plant communities there was an average of only 7.5 cm of snow during late winter 1978. Snow cover was thinner by a ratio of 1:4 compared to control areas.These permafrost features have formed since the White River volcanic ash fall of 1220 BP. On palsas and peat plateaus this ash occurs at an average depth of 21 cm and has an average thickness of 11.6 cm.Shrinkage and (or) total decay of palsas and peat plateaus has occurred during the past 34 years. In one palsa field this represents a 34% reduction of area whereas in two others, 100%. The areal extent of some peat plateaus has also been reduced.

scholarly journals Estimating building vulnerability to volcanic ash fall for insurance and other purposes

2017 ◽  
Vol 6 (1) ◽  
Author(s):  
R. J. Blong ◽  
P. Grasso ◽  
S. F. Jenkins ◽  
C. R. Magill ◽  
T. M. Wilson ◽  
...  
Keyword(s):  
Volcanic Ash ◽  
Building Vulnerability ◽  
Ash Fall

scholarly journals The 852/3 CE Mount Churchill eruption: examining the potential climatic and societal impacts and the timing of the Medieval Climate Anomaly in the North Atlantic Region

2021 ◽  
Author(s):  
Helen Mackay ◽  
Gill Plunkett ◽  
Britta Jensen ◽  
Thomas Aubry ◽  
Christophe Corona ◽  
...  
Keyword(s):  
Tree Ring ◽  
North Atlantic ◽  
Volcanic Ash ◽  
Climate Forcing ◽  
Medieval Climate Anomaly ◽  
North Atlantic Region ◽  
Atlantic Region ◽  
Climate Anomaly ◽  
White River ◽  
The North

Abstract. The 852/3 CE eruption of Mount Churchill, Alaska, was one of the largest first millennium volcanic events, with a magnitude of 6.7 (VEI 6) and a tephra volume of 39.4–61.9 km3 (95 % confidence). The spatial extent of the ash fallout from this event is considerable and the cryptotephra (White River Ash east; WRAe) extends as far as Finland and Poland. Proximal ecosystem and societal disturbances have been linked with this eruption; however, wider eruption impacts on climate and society are unknown. Greenland ice-core records show that the eruption occurred in winter 852/3 ± 1 CE and that the eruption is associated with a relatively moderate sulfate aerosol loading, but large abundances of volcanic ash and chlorine. Here we assess the potential broader impact of this eruption using palaeoenvironmental reconstructions, historical records and climate model simulations. We also use the fortuitous timing of the 852/3 CE Churchill eruption and its extensively widespread tephra deposition of the White River Ash (east) (WRAe) to examine the climatic expression of the warm Medieval Climate Anomaly period (MCA; ca. 950–1250 CE) from precisely linked peatlands in the North Atlantic region. The reconstructed climate forcing potential of 852/3 CE Churchill eruption is moderate compared with the eruption magnitude, but tree-ring-inferred temperatures report a significant atmospheric cooling of 0.8 °C in summer 853 CE. Modelled climate scenarios also show a cooling in 853 CE, although the average magnitude of cooling is smaller (0.3 °C). The simulated spatial patterns of cooling are generally similar to those generated using the tree-ring-inferred temperature reconstructions. Tree-ring inferred cooling begins prior to the date of the eruption suggesting that natural internal climate variability may have increased the climate system’s susceptibility to further cooling. The magnitude of the reconstructed cooling could also suggest that the climate forcing potential of this eruption may be underestimated, thereby highlighting the need for greater insight into, and consideration of, the role of halogens and volcanic ash when estimating eruption climate forcing potential. Precise comparisons of palaeoenvironmental records from peatlands across North America and Europe, facilitated by the presence of the WRAe isochron, reveal no consistent MCA signal. These findings contribute to the growing body of evidence that characterizes the MCA hydroclimate as time-transgressive and heterogeneous, rather than a well-defined climatic period. The presence of the WRAe isochron also demonstrates that no long-term (multidecadal) climatic or societal impacts from the 852/3 CE Churchill eruption were identified beyond areas proximal to the eruption. Historical evidence in Europe for subsistence crises demonstrate a degree of temporal correspondence on interannual timescales, but similar events were reported outside of the eruption period and were common in the 9th century. The 852/3 CE Churchill eruption exemplifies the difficulties of identifying and confirming volcanic impacts for a single eruption, even when it is precisely dated.

Volcanic ash fall impacts

2015 ◽  
pp. 281-288 ◽  
Author(s):  
T.M. Wilson ◽  
S.F. Jenkins ◽  
C. Stewart
Keyword(s):  
Volcanic Ash ◽  
Ash Fall

Quantifying volcanic ash fall hazard to electricity infrastructure

2008 ◽  
Vol 177 (4) ◽  
pp. 1055-1062 ◽  
Author(s):  
Mark Bebbington ◽  
Shane J. Cronin ◽  
Ian Chapman ◽  
Michael B. Turner
Keyword(s):  
Volcanic Ash ◽  
Ash Fall ◽  
Electricity Infrastructure

Estimating the Volcanic Ash Fall Rate from the Mount Sinabung Eruption on February 19, 2018 Using Weather Radar

2019 ◽  
Vol 14 (1) ◽  
pp. 135-150 ◽  
Author(s):  
Magfira Syarifuddin ◽  
Satoru Oishi ◽  
Ratih Indri Hapsari ◽  
Jiro Shiokawa ◽  
Hanggar Ganara Mawandha ◽  
...  
Keyword(s):  
Volcanic Ash ◽  
Elevation Angle ◽  
Training Data ◽  
Classification Model ◽  
Column Height ◽  
Depth Information ◽  
Fall Rate ◽  
Angular Range ◽  
Ash Fall ◽  
Reflectivity Factor

This paper presents a theoretical method for estimating volcanic ash fall rate from the eruption of Sinabung Volcano on February 19, 2018 using an X-band multi-parameter radar (X-MP radar). The X-MP radar was run in a sectoral range height indicator (SRHI) scan mode for 6° angular range (azimuth of 221°–226°) and at an elevation angle of 7° to 40° angular range. The distance of the radar is approximately 8 km in the Southeastern direction of the vent of Mount Sinabung. Based on a three-dimensional (3-D) image of the radar reflectivity factor, the ash column height was established to be more than 7.7 km, and in-depth information on detectable tephra could be obtained. This paper aims to present the microphysical parameters of volcanic ash measured by X-MP radar, which are the tephra concentration and the fall-out rate. These parameters were calculated in a two-step stepwise approach microphysical model using the scaled gamma distribution. The first step was ash classification based on a set of training data on synthetic ash and its estimated reflectivity factor. Using a naïve Bayesian classification, the measured reflectivity factors from the eruption were classified into the classification model. The second step was estimating the volcanic ash concentration and the fall-out rate by power-law function. The model estimated a maximum of approximately 12.9 g·m-3of ash concentration from the coarse ash class (mean diameterDn= 0.1 mm) and a minimum of approximately 0.8 megatons of volcanic ash mass accumulation from the eruption.

Episodic Emergence in the Past 3000 Years at the Akkeshi Estuary, Hokkaido, Northern Japan

2001 ◽  
Vol 56 (2) ◽  
pp. 231-241 ◽  
Author(s):  
Yuki Sawai
Keyword(s):  
Volcanic Ash ◽  
Late Quaternary ◽  
Vertical Crustal Movement ◽  
The Past ◽  
Marine Terraces ◽  
The Pacific ◽  
Tectonically Active ◽  
Emergence Event ◽  
Rapid Emergence ◽  
Northern Japan

AbstractAt the Akkeshi estuary, rapid emergence interrupted Holocene submergence at least four times in the past 3000 years. Each emergence event produced an upward change from estuarine mud to freshwater peat. While the estuarine mud abounds in brackish and marine diatoms, freshwater taxa dominate the peat. Emergence events occurred from 1700 to 2300, 1000 to 1300, and 500 to 700 cal yr B.P. An additional emergence event predated by several decades a volcanic ash that erupted in A.D. 1694. At least three of the events produced contacts abrupt enough to represent uplift during earthquakes. Such uplift may reconcile seemingly conflicting records of vertical crustal movement in eastern Hokkaido. This tectonically active area, which is being subducted by the Pacific plate at 8 cm/yr, contains marine terraces that imply 0.1–0.5 mm/yr of net uplift in the late Quaternary. However, these terraces adjoin tide gages that recorded 8–9 mm/yr of steady submergence in the 20th century. The terrace uplift need not conflict with the gaged submergence if the region is subject to occasional coseismic uplift, as during the emergence events implied by Holocene geology near Akkeshi.

Sign in / Sign up

Export Citation Format

Share Document