Stresses in the Moon

It is argued that a reliable theory of the stress history of the Moon should take into account several factors; and that direct observations of the Moon's surface can throw much light on this subject.     

The influence of rock structures on coast-line and cliff development around Tintagel,North Cornwall

The paper deals with the morphology of the stretch of coast between Boscastle and the Treligga Cliffs in North Cornwall. The prevalent cliff type is slope-over-wall, either hog's-back or bevelled as defined by Miss Arber (1949). Flat-topped cliffs are less common. It is considered that geological structures—bedding, jointing, faulting and, to a lesser extent, rock-type—have not only had considerable influence on the shape of the cliffs, but have also guided the marine attack on the coast. The evolution of most of the coast features, when seen in plan or profile, has been controlled by the local geological structure. The southern stretch of the coast is sub-parallel to seaward-dipping normal faults which have been stripped of their hanging-walls. Such a cliff line is dominantly a faultline scarp which has suffered slight retrogression.     

Submarine slope processes on a fan delta,Howe Sound,British Columbia

Modern side-scan sonar technology was used to resurvey the site of the Howe Sound submarine slide described by Terzaghi. Chutes, hummocky topography, and subparallel scarps indicative of submarine mass movement are widespread. Submarine slope processes appear to be far more important to the development of this coarsegrained fan delta than suspected.     

Semiconductors exposed to oils in pressure-tolerant electronic systems

The present study indicates that most semiconductor components are fabricated such that they are not affected by operation in a dielectric oil environment. A quantitative estimate of the conditions under which oil-soluble ions will invert semiconductor surfaces and interfere with proper device operation is developed. The results are discussed in terms of pressure-tolerant electronic systems—solid-state components operated immersed in chemically inert dielectric oils when these components are subject to, and experience, ambient hydrostatic pressures of the ocean depths. The feasibility of pressure-tolerant electronic systems is demonstrated.     

Evolution des hydrocarbures et des populations bactériennes et microphytiques dans les sédiments des marais maritimes de l'ile grande pollués par l'Amoco cadiz: 2—Evolution des peuplements microphytiques

In this work we attempt to estimate the short- and long-term effects of the Amoco Cadiz oil spill on benthic microalgal populations (cyanophytes and diatoms) which, under natural conditions, live on upper layers of ‘schorres’ soils or of ‘slikke’ muds in the Ile Grande salt marsh system (Côtes du Nord, France). These populations were completely destroyed in 1978 in the oil-affected sites. Ubiquitous species settled fairly rapidly on intertidal polluted muds (tidal flat). The chlorophyll a content values reached 100 μg g⁻¹ dry sediment, i.e. 1000 mg m⁻² in 1980. Conversely, the salt marsh soils are still much less densely repopulated 3 years after the Amoco Cadiz grounding—especially when they are infrequently flooded (3 to 40 μg Chl.a g⁻¹, i.e. 40 to 270 mg m⁻²). Some of these soils remain ten times less populated than reference stations.     

A review of: “An introduction to magnetohydrodynamics”

by P. A. Davidson, Cambridge Texts in Applied Mathematics, Cambridge University Press, 2001, XVIII+431 pp., £ 24.95, paperback (ISBN 0 521 79487 0), £ 70.00, hardback (ISBN 0 521 79149 9).     

Explosive rhyolite tuya formation: classic examples from Kerlingarfjöll,Iceland

Rhyolite eruptions in Iceland mostly take place at long-lived central volcanoes, examples of which are found associated with each of the present-day rift-zone ice caps. Subglacial eruptions at Kerlingarfjöll central volcano produced rhyolite tuyas that are notable for their exposures of early-erupted pyroclastic material. Observations from a number of these edifices are synthesised into a general model for explosive rhyolite tuya formation. Eruptions begin with violent phreatomagmatic explosions that generate massive tuff (mT), but the influence of water quickly declines, leading to the formation of massive lapilli-tuffs (mLT) containing magmatically-fragmented vesicular pumice and ash. These are deposited rapidly near the vent, probably by moist pyroclastic density currents, confined by ice but not within a meltwater lake. The explosive-effusive transition is controlled by the ascent rate and gas content of the magma. An unusual obsidian-rich massive lapilli-tuff lithofacies (omLT) is identified and interpreted as pyroclastic material that was intruded into gas-fluidised deposits at the explosive-effusive transition. The effusive phase of eruption involves the emplacement of intrusions and lava caps. Intrusions of lava into the early-erupted phreatomagmatic deposits are characterised by peperitic margins and the formation of hyaloclastite. Intrusions into stratigraphically higher levels of the pyroclastic material show more limited interaction with the host tephra and have microcrystalline cores. Large lava bodies with columnar-jointed margins cap the tuyas and have intrusive basal contacts with the tephras. The main influence of the ice is to confine the rhyolite eruptive products to immediately above the vent region. This is in contrast to subglacial basaltic tuya-forming eruptions, which are characterised by the formation of meltwater lakes, phreatomagmatic fragmentation and subaqueous deposition. The lack of meltwater storage may reduce the potential for large jökulhlaups.