scholarly journals The products of primary magma fragmentation finally revealed by pumice agglomerates

Geology ◽  
2021 ◽  
Author(s):  
Thomas Giachetti ◽  
Kathleen R. Trafton ◽  
Joshua Wiejaczka ◽  
James E. Gardner ◽  
James M. Watkins ◽  
...  
Keyword(s):  
Potential Energy ◽  
Size Distributions ◽  
Secondary Fragmentation ◽  
Entire Process ◽  
Magma Fragmentation ◽  
Primary Products ◽  
Primary Fragmentation ◽  
Rapid Decompression ◽  
Original Size ◽  
Pumice Aggregates

Following rapid decompression in the conduit of a volcano, magma breaks into ash- to block-sized fragments, powering explosive sub-Plinian and Plinian eruptions that may generate destructive pyroclastic falls and flows. It is thus crucial to assess how magma breaks up into fragments. This task is difficult, however, because of the subterranean nature of the entire process and because the original size of pristine fragments is modified by secondary fragmentation and expansion. New textural observations of sub-Plinian and Plinian pumice lapilli reveal that some primary products of magma fragmentation survive by sintering together within seconds of magma break-up. Their size distributions reflect the energetics of fragmentation, consistent with products of rapid decompression experiments. Pumice aggregates thus offer a unique window into the previously inaccessible primary fragmentation process and could be used to determine the potential energy of fragmentation.

Factors Affecting Primary Fragmentation During Combustion of Serbian Coals

2005 ◽  
Author(s):  
Milijana J. Paprika ◽  
Mirko M. Komatina ◽  
Franz Winter ◽  
Dragoljub V. Dakic
Keyword(s):  
Coal Particle ◽  
Temperature Response ◽  
Coal Bed ◽  
Two Phase ◽  
Factors Affecting ◽  
Fragmentation Behavior ◽  
Bed Temperature ◽  
Primary Fragmentation ◽  
Dynamic Simulation Model ◽  
Original Size

A two-phase experimental method to establish primary fragmentation behavior of Serbian lignites is presented. The first phase was fragmentation quantification, and second was measuring temperature response of center of coal particle during devolatilization. A dynamic simulation model gave thermal properties of coal used. The influence of various factors such as original size of coal, bed temperature, and coal rank on fragmentation is presented and discussed. A new factor, ratio of coal volatile content and coal thermal diffusivity, as representative of heat and mass transfer processes inside of coal particle, has been introduced and its influence on fragmentation index was analyzed.

scholarly journals Supplemental Material: The products of primary magma fragmentation finally revealed by pumice agglomerates

2021 ◽  
Author(s):  
Thomas Giachetti ◽  
et al.
Keyword(s):  
Electron Microscopy ◽  
Computed Tomography ◽  
Scanning Electron Microscopy ◽  
Size Distributions ◽  
Sample Collection ◽  
X Ray ◽  
Additional Information ◽  
Magma Fragmentation ◽  
X Ray Computed ◽  
Scanning Electron

Additional information on (1) the four eruptions studied and sample collection, (2) lapilli selection, (3) measurements of volume and porosity, (4) analysis by X-Ray computed tomography and scanning electron microscopy, and (5) calculation of protopyroclasts size distributions.<br>

Patch Sizes, Area, and Spatial Distribution of Nonforests Are Vital Ingredients to Fire-Adapted Western US Forests

2021 ◽  
Author(s):  
Paul Hessburg
Keyword(s):  
Potential Energy ◽  
Size Distributions ◽  
Bare Ground ◽  
Fire Event ◽  
Forested Area ◽  
Blue Mountains ◽  
Vegetation Height ◽  
Western Us ◽  
Driven System ◽  
Potential Map

&lt;p&gt;&lt;strong&gt;Abstract:&amp;#160; &lt;/strong&gt;In prior published work with reconstructions of early and late 20&lt;sup&gt;th&lt;/sup&gt; century forest landscapes, we were surprised by the large amount of historical meadows, shrubfields, sparse woodlands, and bare ground (hereafter, nonforests) we observed on forest-capable biophysical settings. We also noted a trend of forest encroachment and densification in the late 20&lt;sup&gt;th&lt;/sup&gt;-century. Here, using LANDFIRE remotely sensed, existing vegetation height and cover, and environmental site potential map layers for seven western provinces--rescaled to match the grain of photogrammetric data--we quantitatively compare the area and patch size distributions of early- (E20&lt;sup&gt;th&lt;/sup&gt;), late 20&lt;sup&gt;th&lt;/sup&gt;-century (L20&lt;sup&gt;th&lt;/sup&gt;), and early 21&lt;sup&gt;st&lt;/sup&gt;-century (E21&lt;sup&gt;st&lt;/sup&gt;) nonforest conditions. Our results showed a trend of increasing nonforest area from the E20&lt;sup&gt;th&lt;/sup&gt; to E21&lt;sup&gt;st&lt;/sup&gt;-century and declining forested area in most provinces, with increases occurring primarily in the larger patch sizes. Our results coupled with other reburn modeling research suggest that extensive nonforest patchworks are intimately linked to forest landscape resilience, which is changing in uncharacteristic ways in some provinces. For example, in the Northern and Southern Cascade, and Blue Mountains provinces, we see an uncharacteristic coarsening of the grain by recent fires, while in the Upper Klamath province, we see a return to a large fire event-driven system. In a physical science sense, our results suggest that fire-prone forests -- in the largest context -- function as stored potential energy, and there is an ongoing tug-of-war waged over space and time between factors growing and removing forests. Nonforests on forest capable sites represent areas where stored potential energy has been reduced. Modern changes we observe in forested area foreshadow changes we can expect with climate warming.&lt;/p&gt;

Magma fragmentation by rapid decompression

Nature ◽  
1996 ◽  
Vol 380 (6570) ◽  
pp. 146-148 ◽  
Author(s):  
Mikhail Alidibirov ◽  
Donald B. Dingwell
Keyword(s):  
Magma Fragmentation ◽  
Rapid Decompression

scholarly journals Supplemental Material: The products of primary magma fragmentation finally revealed by pumice agglomerates

2021 ◽  
Author(s):  
Thomas Giachetti ◽  
et al.
Keyword(s):  
Electron Microscopy ◽  
Computed Tomography ◽  
Scanning Electron Microscopy ◽  
Size Distributions ◽  
Sample Collection ◽  
X Ray ◽  
Additional Information ◽  
Magma Fragmentation ◽  
X Ray Computed ◽  
Scanning Electron

Additional information on (1) the four eruptions studied and sample collection, (2) lapilli selection, (3) measurements of volume and porosity, (4) analysis by X-Ray computed tomography and scanning electron microscopy, and (5) calculation of protopyroclasts size distributions.<br>

scholarly journals Technical Note: An empirical algorithm estimating dry deposition velocity of fine, coarse and giant particles

2014 ◽  
Vol 14 (7) ◽  
pp. 3729-3737 ◽  
Author(s):  
L. Zhang ◽  
Z. He
Keyword(s):  
Dry Deposition ◽  
Fine Particles ◽  
Deposition Velocity ◽  
Aerodynamic Resistance ◽  
Technical Note ◽  
Size Distributions ◽  
Area Index ◽  
Gravitational Settling ◽  
Dry Deposition Velocity ◽  
Original Size

Abstract. An empirical algorithm is developed for calculating bulk dry deposition velocity (Vd) of fine (PM2.5) – particles having a diameter of ≤ 2.5 μm), coarse (PM2.5−10 – particles having a diameter of 2.5–10 μm), and giant (PM10+ – particles having a diameter of > 10 μm) atmospheric particles. The algorithm is developed from an empirical fit of Vd data calculated using the size-resolved Vd scheme of Zhang et al. (2001) with assumed lognormal size distributions of PM2.5, PM2.5−10 and PM10+. In the new algorithm, the surface deposition velocity (Vds) is parameterized as a simple linear function of friction velocity (u*) for PM2.5 and as a polynomial function of u* for both PM2.5−10 and PM10+ over all the 26 land use categories (LUCs). An adjustment factor as an exponential function of u* and leaf area index (LAI) is also applied to Vds of PM2.5−10 and PM10+ over 9 of the 26 LUCs that have variable LAI. Constant gravitational settling velocities are provided for PM2.5, PM2.5−10 and PM10+. Aerodynamic resistance between a reference height and the surface can be calculated using available analytical formulas from the literature. The bulk Vd of PM2.5, PM2.5−10 and PM10+ at the reference height can then be calculated by combining the gravitational settling velocity, aerodynamic resistance and the parameterized Vds. Vd values calculated using the new algorithm are within ±20% of those using the original size-resolved scheme for fine, coarse and giant particles. Uncertainties in Vd values from the new algorithm due to the pre-assumed size distributions are on the order of 20% for fine particles and on the order of a factor of 2.0 for coarse and giant particles. The new algorithm provides an alternative approach for calculating Vd of bulk aerosol particles. Vd of any particulate species can be simply estimated using this scheme as long as the mass fractions in fine, coarse and giant particles are known or can be assumed.

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