Part 2. The deeper structure of the Atlantic - Geological hypotheses and the earth's crust under the oceans

1954 ◽  
Vol 222 (1150) ◽  
pp. 341-348 ◽  
Keyword(s):  
Heat Flow ◽  
Recent Work ◽  
Sea Water ◽  
Volcanic Rocks ◽  
The Other ◽  
Ocean Floor ◽  
Peridotite Xenoliths ◽  
The Earth ◽  
Southern Rhodesia ◽  
Mohorovičić Discontinuity

Recent work has determined the depth of the Mohorovičić discontinuity at sea and has made it likely that peridotite xenoliths in basaltic volcanic rocks are samples of material from below the discontinuity. It is now possible to produce a hypothetical section showing the transition from a continent to an ocean. This section is consistent with both the seismic and gravity results. The possible reactions of the crust to changes in the total volume of sea water are dis­cussed. It seems possible that the oceans were shallower and the crust thinner in the Archean than they are now. If this were so, some features of the oldest rocks of Canada and Southern Rhodesia could be explained. Three processes are described that might lead to the formation of oceanic ridges; one of these involves tension, one compression and the other quiet tectonic conditions. It is likely that not all ridges are formed in the same way. It is possible that serpentization of olivine by water rising from the interior of the earth plays an important part in producing changes of level in the ocean floor and anomalies in heat flow. Finally, a method of reducing gravity observations at sea is discussed.

A new Variety of Anopheles funestus, Giles, from Southern Rhodesia

1930 ◽  
Vol 21 (2) ◽  
pp. 125-126 ◽  
Author(s):  
H. S. Leeson
Keyword(s):  
Close Association ◽  
Anopheles Funestus ◽  
Tropical Medicine ◽  
The Other ◽  
London School ◽  
New Variety ◽  
The Earth ◽  
Blackwater Fever ◽  
Southern Rhodesia ◽  
Surface Drains

While investigating the Anophelini of Southern Rhodesia in connection with the research on blackwater fever conducted by the London School of Hygiene and Tropical Medicine, an undescribed variety of Anopheles funestus, Giles, was taken in the dry season. Nine males and eight females were collected from May to August 1927, near Shamva, and one male and one female in July 1928, in the Fungwi Native Reserve. All were caught out-of-doors except two females, one of which was taken in a shed constructed of grass and the other in a native hut. The remainder were taken in close association with the earth; in surface drains, caves and crevices in rocks. No specimens were taken in or near European habitations, but all in undeveloped country. No adults were bred out, so that the following description is based on individuals captured “wild.” The larva is unknown.

scholarly journals IV. The transmission of electric waves over the surface of the Earth

1915 ◽  
Vol 215 (523-537) ◽  
pp. 105-131 ◽  
Keyword(s):  
Sea Water ◽  
Wave Length ◽  
Diffraction Theory ◽  
The Other ◽  
Critical Survey ◽  
The Earth ◽  
Theoretical Investigations ◽  
The Waves ◽  
Perfect Conduction ◽  
Electric Waves

1. Ever since the time, about 1902, when Marconi first succeeded in sending wireless signals across the Atlantic the question of explaining the mechanism of such transmission has attracted attention among mathematicians. The question may be put in the following form:—The electric waves generated by the sending apparatus differ from waves of light only by having a longer wave-length, which is, nevertheless small compared with the radius of the earth; and the curved surface of the earth may therefore be expected to form a sort of shadow, effectively screening the receiving apparatus at a distance. How, then, does it happen that in practice the waves penetrate into the region of the shadow ? Unfortunately, the question has been investigated by different methods without adequate co-ordination, and the results that have been obtained are somewhat discordant. In these circumstances it appears to be desirable to undertake a critical survey of the question. The various theoretical investigations may be classified as developments of three suggestions: (l) The imperfectly conducting quality, or resistance, of the material, generally sea-water, over which the transmission takes place, may cause the effect observable at a distance to be greater than it would be if the material were perfectly conducting. (2) Owing to the numerical relations connecting the actual wave-lengths used in practice, the size of the earth, and the distances involved, the amount of diffraction, even in the case of perfect conduction, may be greater than would, at first sight, be expected. (3) Transmission through the atmosphere may be notably different from transmission through a homogeneous dielectric. We may refer to these suggestions briefly as the “resistance theory,” the “diffraction theory,” and the “atmospheric theory.” It may be said at once that the atmospheric theory has arisen from the alleged failure of the other two, and that it has not yet been formulated in such a way as to admit of being tested in the same precise analytical fashion as they can. It is still rather speculative and indefinite. In what follows I propose to attend chiefly to the first two suggestions, and to investigate the result that can be obtained by combining them.

The sulfur content of Archean volcanic rocks and a comparison with ocean floor basalts

1978 ◽  
Vol 15 (5) ◽  
pp. 715-728 ◽  
Author(s):  
A. J. Naldrett ◽  
A. M. Goodwin ◽  
T. L. Fisher ◽  
R. H. Ridler
Keyword(s):  
Major Element ◽  
Sea Water ◽  
Volcanic Rocks ◽  
Direct Interaction ◽  
Ocean Floor ◽  
Major Element Composition ◽  
Lake Of The Woods ◽  
Fe Content ◽  
Greenstone Belts ◽  
Archean Greenstone Belts

In this paper we report the sulfur contents of 1056 basalts, andesites, dacites and rhyolites of known major element composition from the Rankin–Ennadai, Birch Lake – Uchi Lake, Lake of the Woods – Wabigoon Lake, Timmins and Skead Archean greenstone belts of the Canadian Shield. The sulfur contents of 299 ocean floor basalts and 68 sub-aerial or shallow water extrusive rocks are also reported. Sulfur contents for rocks of a given class are highly variable, ranging from near zero to several thousand parts per million (ppm). However, when averages for each of the rock classes are examined, the data from the two best documented of the Archean greenstone belts exhibit the same positive correlation between sulfur and total Fe content of the rocks. The trend for the Rankin–Ennadai belt coincides almost exactly with that reported earlier for the Blake River Group, approximating that expected if the rocks were saturated in sulfide at the time of extrusion. Rocks from the Lake of the Woods – Wabigoon Lake, Timmins and Skead areas seem to be somewhat poorer in sulfur than those from the Rankin–Ennadai and Blake River belts.Despite the fact that all evidence in the literature for fresh glassy pillow rims indicates that modern ocean floor basalts are saturated in sulfide, our average values for these ocean floor rocks are much lower than the predicted saturation levels, suggesting that the rocks have lost one-half to three-fourths of their sulfur, presumably through reaction with sea water. It is suggested that the reason for the Archean basalts retaining most of their sulfur despite the extensive redistribution that has occurred, whereas modern ocean floor basalts lose so much, may be due to the Archean rocks accumulating much more quickly and being exposed to direct interaction with sea water for a much shorter time than the modern rocks.

Velocity of elastic waves and structure of the crust in the vicinity of Ottawa, Canada*

1942 ◽  
Vol 32 (4) ◽  
pp. 249-255
Author(s):  
Ernest A. Hodgson
Keyword(s):  
Elastic Waves ◽  
Single Point ◽  
Focal Depth ◽  
The Other ◽  
Northern Europe ◽  
Earth Structure ◽  
Travel Times ◽  
Arrival Times ◽  
The Earth ◽  
Mohorovičić Discontinuity

Summary Ten seismograms, due to rockbursts at Lake Shore Mines, Kirkland Lake, Ontario, were recorded on a Benioff seismograph at Ottawa at a distance of 450 km. (279 mi.). The center of each burst was located within a few feet; but, for the purpose of preparing travel-time tables, they may all be considered to have occurred at a single point at the surface. Two of the bursts were accurately timed on the seismograph at the mine. Six phases were registered on each seismogram, being more sharply marked on some records than on others. Five of these are well defined on nearly all the records. It is thus possible to deduce a set of arrival times at a distance of 450 km. for a burst (or earthquake) occurring at the surface; and this set of times is known with fair precision, since all the readings may be combined. The distance is determined within one part in 7000, the depth within 2000 ft. and the travel times with an error of ±.5 sec. These travel times have been compared with those obtained by Joliat in computing his Tables for Near Earthquakes, based on the velocities deduced by Jeffreys for northern Europe and arbitrarily assuming an earth structure with two layers above the Mohorovičić discontinuity. The differences are minor and are to be explained as chiefly owing to the fact that Joliat assumed the focus to lie at the bottom instead of the top of the upper layer. On the strength of the comparisons afforded by the ten seismograms, the focal time of each burst may be considered as known within ±.5 sec. One of the bursts was so severe that it was registered also at Shawinigan Falls, Quebec (Δ = 576 km., 358 mi.) and at Weston, Massachusetts (Δ = 935 km., 581 mi.). These records will afford a means of deducing the earth structure and velocities in the vicinity of Ottawa, and will permit the construction of tables for rock-bursts and blasts in that area up to 10° (1110 km., 690 mi.). These will be prepared and issued, together with corrections permitting their being used for local earthquakes with finite focal depth. Should other bursts occur later at Kirkland Lake, timed by the mine seismograph and registered at Ottawa or the other stations, the data so made available may be directly used to check and add precision to the deductions made from the seismograms already in hand. Such further data would be most valuable.

A Model for Chemical Exchange in the Basalt–Seawater System of Oceanic Layer II

1973 ◽  
Vol 10 (6) ◽  
pp. 799-816 ◽  
Author(s):  
Roger A. Hart
Keyword(s):  
Steady State ◽  
Heat Flow ◽  
Oceanic Crust ◽  
Chemical Reaction ◽  
Strong Influence ◽  
Sea Water ◽  
Chemical Exchange ◽  
Ocean Floor ◽  
Retrograde Metamorphism ◽  
Alteration Minerals

In this paper evidence is presented in support of the hypothesis that the upper 2-3 km of oceanic layer II is a zone of chemical reaction between seawater and the oceanic crust as it moves away from the mid-ocean ridges.A model is constructed assuming that the principal alteration products resulting from the action of sea-water on primary basalts are:1. K-rich smectite formed during weathering of basalt,2. chlorite formed during retrograde metamorphism, and3. albite–actinolite formed during primary greenschist metamorphisms at the ridge crest.These three processes in combination could extract most of the stream input of K+, Mg2+, and Na+ and add SiO2, Ca2+, Fe2+, and Mn2+ to the ocean systems in amounts comparable to stream input.The steady state reaction of basalt with interstitial seawater to produce alteration minerals could exercise a strong influence in the chemistry of seawater and release energy in amounts sufficient to form a portion of normal heat flow measured on the ocean floor.

Note on Selection of Coordinate Systems for Geodynamics

1975 ◽  
Vol 26 ◽  
pp. 395-407
Author(s):  
S. Henriksen
Keyword(s):  
Sea Level ◽  
The Other ◽  
Coordinate Systems ◽  
Mean Sea Level ◽  
The Earth ◽  
The One ◽  
Static Systems ◽  
Selection Of

The first question to be answered, in seeking coordinate systems for geodynamics, is: what is geodynamics? The answer is, of course, that geodynamics is that part of geophysics which is concerned with movements of the Earth, as opposed to geostatics which is the physics of the stationary Earth. But as far as we know, there is no stationary Earth – epur sic monere. So geodynamics is actually coextensive with geophysics, and coordinate systems suitable for the one should be suitable for the other. At the present time, there are not many coordinate systems, if any, that can be identified with a static Earth. Certainly the only coordinate of aeronomic (atmospheric) interest is the height, and this is usually either as geodynamic height or as pressure. In oceanology, the most important coordinate is depth, and this, like heights in the atmosphere, is expressed as metric depth from mean sea level, as geodynamic depth, or as pressure. Only for the earth do we find “static” systems in use, ana even here there is real question as to whether the systems are dynamic or static. So it would seem that our answer to the question, of what kind, of coordinate systems are we seeking, must be that we are looking for the same systems as are used in geophysics, and these systems are dynamic in nature already – that is, their definition involvestime.

Extending Epistemic Virtue

2018 ◽  
Author(s):  
Heather Battaly
Keyword(s):  
Recent Work ◽  
Virtue Epistemology ◽  
Extended Cognition ◽  
The Other ◽  
Epistemic Virtue ◽  
Virtue Responsibilism

What would happen if extended cognition (EC) and virtue-responsibilism (VR) were to meet? Are they compatible, or incompatible? Do they have projects in common? Would they, as it were, end their meeting early, or stick around but run out of things to say? Or, would they hit it off? This chapter suggests that VR and EC are not obviously incompatible, and that each might fruitfully contribute to the other. Although there has been an explosion of recent work at the intersection of virtue epistemology and EC, this work has focused almost exclusively on the reliabilist side of virtue epistemology. Little has been said about the intersection of VR and EC. This chapter takes initial steps toward filling that gap.

scholarly journals Geocomputing, New Technologies and Historical Analysis: Tools for a Changing Planet

Proceedings ◽  
2019 ◽  
Vol 30 (1) ◽  
pp. 9
Author(s):  
Sebastiano Trevisani
Keyword(s):  
Quantitative Analysis ◽  
Philosophy Of Science ◽  
New Technologies ◽  
Historical Analysis ◽  
Holistic Approach ◽  
Research Topic ◽  
The Other ◽  
Historical Records ◽  
The Earth ◽  
The Relationship

Modern Earth Scientists need also to interact with other disciplines, apparently far from the Earth Sciences and Engineering. Disciplines related to history and philosophy of science are emblematic from this perspective. From one side, the quantitative analysis of information extracted from historical records (documents, maps, paintings, etc.) represents an exciting research topic, requiring a truly holistic approach. On the other side, epistemological and philosophy of science considerations on the relationship between geoscience and society in history are of fundamental importance for understanding past, present and future geosphere-anthroposphere interlinked dynamics.

scholarly journals The Critical Raw Materials Issue between Scarcity, Supply Risk, and Unique Properties

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 1826
Author(s):  
Mihaela Girtan ◽  
Antje Wittenberg ◽  
Maria Luisa Grilli ◽  
Daniel P. S. de Oliveira ◽  
Chiara Giosuè ◽  
...  
Keyword(s):  
Scientific Community ◽  
Chemical Elements ◽  
Raw Materials ◽  
The Other ◽  
Innovation Networks ◽  
Supply Risk ◽  
European Cooperation ◽  
Research And Innovation ◽  
The Earth ◽  
Critical Raw Materials

This editorial reports on a thorough analysis of the abundance and scarcity distribution of chemical elements and the minerals they form in the Earth, Sun, and Universe in connection with their number of neutrons and binding energy per nucleon. On one hand, understanding the elements’ formation and their specific properties related to their electronic and nucleonic structure may lead to understanding whether future solutions to replace certain elements or materials for specific technical applications are realistic. On the other hand, finding solutions to the critical availability of some of these elements is an urgent need. Even the analysis of the availability of scarce minerals from European Union sources leads to the suggestion that a wide-ranging approach is essential. These two fundamental assumptions represent also the logical approach that led the European Commission to ask for a multi-disciplinary effort from the scientific community to tackle the challenge of Critical Raw Materials. This editorial is also the story of one of the first fulcrum around which a wide network of material scientists gathered thanks to the support of the funding organization for research and innovation networks, COST (European Cooperation in Science and Technology).

scholarly journals Note on terrestrial radiation

1883 ◽  
Vol 35 (224-226) ◽  
pp. 21-25
Keyword(s):  
Radiant Heat ◽  
The Other ◽  
Cotton Wool ◽  
The Earth ◽  
Meteorological Observations

On Hind Head, a fine moorland plateau about three miles from Haslemere, with an elevation of 900 feet above the sea, I have recently erected a small iron hut, which forms, not only a place of rest, but an extremely suitable station for meteorological observations. Here, since the beginning of last November, I have continued to record from time to time the temperature of the earth’s surface as compared with that of the air above the surface. My object was to apply, if possible, the results which my experiments had established regarding the action of aqueous vapour upon radiant heat. Two stout poles about 6 feet high were firmly fixed in the earth 8 feet asunder. From one pole to the other was stretched a string, from the centre of which the air thermometer was suspended. Its bulb was 4 feet above the earth. The surface thermometer was placed upon a layer of cotton wool, on a spot cleared of heather, which thickly covered the rest of the ground. The outlook from the thermometers was free and extensive; with the exception of the iron hut just referred to, there was no house near, the hut being about 50 yards distant from the thermometers.

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