Effects of Mountain Pine Beetle on Fuels and Expected Fire Behavior in Lodgepole Pine Forests, Colorado, USA

In Colorado and southern Wyoming, mountain pine beetle (MPB) has affected over 1.6 million ha of predominantly lodgepole pine forests, raising concerns about effects of MPB-caused mortality on subsequent wildfire risk and behavior. Using empirical data we modeled potential fire behavior across a gradient of wind speeds and moisture scenarios in Green stands compared three stages since MPB attack (Red [1–3 yrs], Grey [4–10 yrs], and Old-MPB [∼30 yrs]). MPB killed 50% of the trees and 70% of the basal area in Red and Grey stages. Across moisture scenarios, canopy fuel moisture was one-third lower in Red and Grey stages compared to the Green stage, making active crown fire possible at lower wind speeds and less extreme moisture conditions. More-open canopies and high loads of large surface fuels due to treefall in Grey and Old-MPB stages significantly increased surface fireline intensities, facilitating active crown fire at lower wind speeds (>30–55 km/hr) across all moisture scenarios. Not accounting for low foliar moistures in Red and Grey stages, and large surface fuels in Grey and Old-MPB stages, underestimates the occurrence of active crown fire. Under extreme burning conditions, minimum wind speeds for active crown fire were 25–35 km/hr lower for Red, Grey and Old-MPB stands compared to Green. However, if transition to crown fire occurs (outside the stand, or within the stand via ladder fuels or wind gusts >65 km/hr), active crown fire would be sustained at similar wind speeds, suggesting observed fire behavior may not be qualitatively different among MPB stages under extreme burning conditions. Overall, the risk (probability) of active crown fire appears elevated in MPB-affected stands, but the predominant fire hazard (crown fire) is similar across MPB stages and is characteristic of lodgepole pine forests where extremely dry, gusty weather conditions are key factors in determining fire behavior

A transmission electron microscope study of white mica crystallite size distribution in a mudstone to slate transitional sequence, North Wales, UK

High-resolution transmission electron microscopy (HRTEM) measurements of the thickness of white mica crystallites were made on three pelite samples that represented a prograde transition from diagenetic mudstone though anchizonal slate to epizonal slate. Crystallite thickness, measured normal to (001), increases as grade increases, whereas the XRD measured 10 Å peak-profile, the Kubler index, decreases. The mode of the TEM-measured size population can be correlated with the effective crystallite size N (001) determined by XRD. The results indicate that the Kubler index of white mica crystallinity measures changes in the crystallite size population that result from prograde increases in the size of coherent X-ray scattering domains. These changes conform to the Scherrer relationship between XRD peak broadening and small crystallite size. Lattice ‘strain’ broadening is relatively unimportant, and is confined to white mica populations in the diagenetic mudstone. Rapid increases in crystallite size occur in the anchizone, coincident with cleavage development. Changes in the distribution of crystallite thickness with advancing grade and cleavage development are characteristic of grain-growth by Ostwald ripening. The Kubler index rapidly loses sensitivity as an indicator of metapelitic grade within the epizone.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47293/1/410_2004_Article_BF00306406.pd

Occurrence of wide-chain Ca-pyriboles as primary crystals in the Salton Sea Geothermal Field, California, USA

Amphiboles and pyroxenes occurring in the Salton Sea Geothermal Field were found to contain coherent intergrowths of chain silicates with other than double and single chain widths by using transmission and analytical electron microscopy. Both occur in the biotite zone at the temperature (depth) interval of 310° C (1,060 m) to 330° C (1,547m) which approximately corresponds to temperatures of the greenschist facies. The amphiboles occur as euhedral fibrous crystals occupying void space and are composed primarily of irregularly alternating (010) slabs of double or triple chains, with rare quadruple and quintuple chains. Primary crystallization from solution results in euhedral crystals. Clinopyroxenes formed mainly as a porefilling cement and subordinately as prismatic crystals coexisting with fibrous amphiboles. Fine lamellae of double and triple chains are irregularly intercalated with pyroxene. AEM analyses yield formulae (Ca 1.8 Mg 2.9 Fe 1.9 Mn 0.1 ) Si 8 O 21.8 (OH) 1.8 (310° C) and (Ca 2.0 Fe 2.5 Mg 2.3 ) Si 8 O 21.8 (OH) 2.0 (330° C) for amphiboles and (Ca 1.1 Fe 0.6 Mg 0.3 ) Si 2 O 6 for clinopyroxene. Thermodynamic calculations at P fluid =100 bar of equilibrium reactions of (1) 3 chlorite +10 calcite + 21 quartz = 3 actinolite + 2 clinozoisite + 8 H 2 O + 10 CO 2 and (2) actinolite+ 3 calcite+ 2 quartz = 5 clinopyroxene + H 2 O + 3 CO 2 using Mg-end member phases indicate that formation of amphibole and pyroxene require very water-rich conditions at temperatures below 330° C.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47344/1/410_2004_Article_BF00371233.pd

Phlogopite-chlorite reaction mechanisms and physical conditions during retrograde reactions in the Marble Formation, Franklin, New Jersey

A retrograde assemblage in a specimen from the Franklin Marble Formation containing an unusual occurrence of three micas has been studied. Microprobe analyses of the margarite, muscovite and phlogopite reveal significant sodium and fluorine but otherwise show little mutual solid solution. The conditions that prevailed during the retrogression estimated from phase equilibria are T =370–450° C and =0.03–0.3 at an assumed pressure of 2 kb.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47339/1/410_2004_Article_BF00380175.pd

An analytical electron microscopic study of a pyroxene-amphibole intergrowth

Samples of a garnet granulite from the mafic border units of the Lake Chatuge, Georgia alpine peridotite body were found to contain lamellar intergrowths of a pargastic amphibole in augite having the typical appearance of an exsolution feature. Single crystal X-ray diffraction, optical, electron microprobe and conventional and analytical electron microscopic studies have provided data limiting the compositions and structures of the coexisting phases. Individual lamellae of both materials are from 0.5 to 2.0 μm in width with the lamellar interface parallel to {0 1 0}. The formulae of the minerals, as determined by a combination of electron microprobe and analytical electron microscopy, are (Na 0.1 Ca 1.0 Mg 0.6 Fe 3+ 0.3 )(Si 1.8 Al 0.2 )O 6 for the pyroxene and Na 0.7 Ca 1.9 (Mg 2.1 Fe 2+ 1.4 Fe 3+ 0.5 Ti 0.1 Cr 0.1 Al 0.8 )(Si 5.9 Al 2.1 ) O 22 (OH) 2 for the amphibole. Several other studies have described intergrowths similar to those observed in this work, in general favoring exsolution as the formation mechanism for the intergrowths. In the Lake Chatuge samples however, replacement of pyroxene by amphibole is in part indicated by continuous gradation of amphibole lamellae into amphiboles rimming the clinopyroxenes.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47333/1/410_2004_Article_BF00636515.pd

Evaluating YouTube videos for young children

YouTube has become a popular digital media platform used by young children. However, concerns have been raised around inappropriate video content and limited quality. A lack of research and theoretical discussion exists on how best to evaluate the quality of YouTube videos made for children. In this study, we reviewed research and developed a set of design principles that informed the production of a YouTube video rubric used to evaluate the quality of YouTube videos targeted at young children 0 to 8 years old. The four key evaluation criteria used are: Age appropriateness, Content quality, Design features, and Learning objectives. This evaluation tool has the potential to be used by educators to assess the quality of videos for early learning and guide YouTube creators in their production of educational videos for young children