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In basaltic glass from the southern Mid-Atlantic-Ridge conducive environmental conditions for biogenic weathering resulted in excellent preserved microbial morphologies on glass surfaces. The disti...

Basaltic pahoehoe lavas weather on time scales of decades to millennia and are chemically altered by volcanic heat and gases on time scales of days to decades following their eruption. Despite differences in reactions and rates, the end products, viewed spectrally in the thermal infrared TIR: 8–12 μm, are similar and distinctive: initial rinds of quickly cooled, disordered glass with broad emissivity minima at 9–11 μm devitrify to yield a sharper emissivity band at 9.1 μm; opaline rinds with a similar emissivity feature accrete and gradually transition to cryptocrystalline quartz with an emissivity minimum near 8.1 μm. Ultimately, exposed surfaces are oxidized and hydrated to palagonite, with a loss of spectral contrast and character. We have collected over 600 pahoehoe samples of different ages from seven sites on Mauna Loa and the south coast of Hawai‘i in order to measure hemispheric emissivity spectra and compare them to airborne and spaceborne TIR Advanced Spaceborne Thermal Emission and Reflection Radiometer ASTER AST05 emissivity images of Hawai‘i. ASTER, with five 90 m TIR bands, has operated over the 11 year period since launch in late 1999. Images and samples from some of the Hawai‘ian sites were collected repeatedly over a decade or more to study the rate of spectral change there. Continuing eruptions of Pu‘u ‘O‘o since 1983 offered an opportunity to study the effects of a persistent dousing of lavas by acidic rain and air ‘vog’, and older flows from Mauna Loa offered an opportunity to study the effects of weathering away from active vents. Weathering changes and rates quantified spectrally are helpful in mapping and assessing long-term environments on volcanoes.

Bacteria play an important role in rock weathering and yet their diversity and potential activity in the terrestrial rock weathering environment is poorly understood. Culture and culture-independent methods (16S rDNA) were used to investigate the populations of bacteria inhabiting a basaltic glass/palagonite subglacial (hyaloclastite) deposit subject to weathering in Iceland. The rock hosts a diverse microbial community. The 16S rDNA clones were dominated by Actinobacteria, Proteobacteria, Bacteroidetes and Acidobacteria. Representatives of Gemmatimonadetes and Verrucomicrobia were present. Isolation of organisms on basalt/palagonite yielded only two isolates, an actinobacterium and a Bacteroidetes, showing that the active species, at least in the time scale of laboratory cultivation, are a small proportion of the total diversity. Firmicutes and Actinobacteria were isolated when basalt/palagonite was supplemented with an organic source. Many of the isolates demonstrated tolerance to transition metals (Cr,...

Central Scania, southernmost Sweden, is penetrated by more than one hundred basaltic volcanic necks of Jurassic age. Pyroclastics, related to the volcanic necks, have been investigated to reveal the volcanic environment, and the eruptive character required to produce the pyroclastics. Based on textural and petrographical evidence, a Strombolian-type eruptive character is suggested. The sediment, a lapilli tuff, is clay altered due to early diagenetic processes, but traces of palagonite reveal a former basaltic composition of the lapilli tuff. The volcanoes were part of a monogenetic volcanic field and deposition of the pyroclastic sediment took place on land, probably close to oceanic water.

The Pleistocene lavas and palagonite tuffs of Aitutaki form a nephelinic suite dominated by olivine nephelinite with lesser amounts of basanite. In age, composition, and occurrence, the volcanic rocks of Aitutaki are similar to the Honolulu Group on Oahu in the Hawaiian Islands. Major and trace element analyses of six olivine nephelinites and two basanites are reported. These show that olivine nephelinite is the more fractionated lava, but cannot be derived from a parental basanite magma because neither high-pressure nor low-pressure mineral fractionation schemes can account for the observed chemical differences. The olivine nephelinite may result from a smaller degree of partial fusion at greater depth in the upper mantle than the basanite. Both melts were probably hydrous, but olivine nephelinite may also have contained CO2

(1900). The glacial palagonite‐formation of Iceland. Scottish Geographical Magazine: Vol. 16, No. 5, pp. 265-293.

Surtsey is the newest member of a group of islands named Vestmannaeyjar (Westmann Islands) off the southern coast of Iceland. All the islands are of volcanic origin with palagonite tuff or basaltic lava. The eruption, which gradually built up Surtsey, started on 14 November 1963 and lasted over 3.5 yr. The island reached the size of 2.7 km2. In the spring of 1964 the first biological observations were performed on the island and the vascular plants have been investigated annually since 1965, when the first plant was discovered growing on Surtsey. The investigation of colonization of vascular plants on Surtsey involves the study of source of available species, means of dispersal, types of habitats on the island, and performance of the plants. The amount of plant material dispersing to Surtsey is in reverse proportion to the distance to the source of available plants, the nearest one being a rock 5.1 km away, but from the mainland the distance for dispersal is over 35 km. The Surtsey ecosystem is still immature and only pioneer organisms are present. By 1986 about 23 species of vascular plants have been recorded growing there and only a few coastal species have become successful colonizers. The sandwort Honkenya peploides has been the most prolific. In 1978, it showed a tendency towards the formation of an association with lyme grass, Elymus arenarius, and later with lungwort, Mertensia maritima. A study of the establishment of vegetation by pioneers