Pigeons at Magnetic Anomalies: The Effects of Loft Location

1992 ◽  
Vol 170 (1) ◽  
pp. 127-141 ◽  
Author(s):  
CHARLES WALCOTT

Homing pigeons from our old lofts at Fox Ridge Farm in Lincoln, MA, were disoriented when released at places where the earth's magnetic field was irregular-so-called ‘magnetic anomalies’. The orientation of pigeons raised in our lofts at Cornell in Ithaca, NY, was unaffected by anomalies. Further experiments in Lincoln showed that sibling pigeons raised and trained to lofts only 2.5 km apart behaved differently when released at a strong magnetic anomaly. Pigeons from the loft situated in a magnetic gradient of 450 nT km−1 were disoriented at anomalies, whereas birds raised in a loft in a magnetic gradient of 88nT km−1 were well oriented. This suggests that the location of the home loft may play an important role in determining which cues pigeons use for their navigation, and that these cues are learned sometime after weaning from their parents at 4–6 weeks after hatching.

Geophysics ◽  
1941 ◽  
Vol 6 (1) ◽  
pp. 1-12 ◽  
Author(s):  
J. W. Fisher

Calculations are made of gravitational and magnetic anomalies supposed due to local variations in the form of a single differential surface separating an overlying rock from an underlying one, the effective thickness of the latter being infinite. Both layers are homogeneous in density or magnetic susceptibility and only those magnetic effects are considered which are due to induction in the earth’s magnetic field. The maximum possible values of these anomalies and of their first and second horizontal derivatives are calculated under these simplified conditions, and it is pointed out that the numerical readings of these quantities, provided by survey results, may lead to useful estimates of the extreme depth and proportions of the structure responsible.


1981 ◽  
Vol 18 (3) ◽  
pp. 657-661 ◽  
Author(s):  
R. L. Coles ◽  
G. V. Haines ◽  
W. Hannaford

Profiles of anomalies in the vertical component of the Earth's magnetic field over central and eastern Canada, observed at an average altitude of 4 km above sea level, show broad regions with distinctive anomaly character. These subdivisions indicate major differences in the evolutions of regions within individual structural provinces. Particularly notable is a region of intense anomalies in the northern part of the Superior Province in Quebec, contrasting with much weaker anomaly relief to the south and east.


Author(s):  
William Lowrie

The Earth is surrounded by a magnetic field, which originates inside its molten core, and which for centuries has helped travellers to navigate safely across uncharted regions. The magnetic field protects life on the Earth by acting as a shield against harmful radiation from space, especially from the Sun. ‘The Earth’s magnetic field’ explains that the magnetic field at the Earth’s surface is dominantly that of an inclined dipole. The Sun’s deforming effect on the magnetic field outside the Earth is described, as are the magnetic fields of other planets. The magnetism of rocks forms the basis of palaeomagnetism, which explains how plate tectonics displaced the continents and produced oceanic magnetic anomalies whenever the geomagnetic field reversed polarity.


2020 ◽  
Vol 53 (2C) ◽  
pp. 13-25
Author(s):  
Basim Hijab

The relationships of the Earth’s magnetic field intensity and time (the past 320 years) for many locations around the world are obtained, based on the IGRF-13 mathematical model. The results showed that each location on the earth surface has its magnetic intensity relation with time that reflects local variations. The sudden changes (magnetic anomalies) in the Earth’s magnetic field with time are natural phenomena, which are different from place to another. These magnetic anomalies are investigated for possible relationship to the historical records of the influenza pandemic outbreaks. The results showed clear congruences between the Earth’s magnetic anomalies and influenza outbreaks times. The congruences become clearer when comparing the highest magnetic anomaly intensity and the first outbreak location of the influenza pandemic. This is true for the recorded historical data since 1890 AD. It is not known how the changes in Earth’s magnetic field affect the virus’s outbreaks or evolution, but there is a clear relation that needs detailed studies.


Author(s):  
Aleksey Schitov ◽  
Oleg Dobroserdov ◽  
Sergey Frolov ◽  
Ludmila Semenova

The paper deals with the use of the small spacecraft ECUADOR-UTE (HC1PX) designed to conduct space experiments in autonomous flight conditions and, in particular, to measure the Earth’s electromagnetic field and study the ionosphere. The spacecraft has a built-in target load module, including a precision magnetometer that measures the Earth’s magnetic field. The measurement results are used to study the properties and state of the circumterranean environment including magnetic anomalies. The latter may indicate certain tectonic structures in the sedimentary stratum, which are indicators of oil and gas, and magnetic pole displacement processes. Measurement results can also be used for prediction and forecasting efforts in anomalouszones. The compiled analytical dependences for the anomalous zones can serve as a forecasting device when studying the magnetic tension of the Earth’s geographic regions by means of a spacecraft. Measuring the magnetic anomalies of the Earth’s surface is should prove necessary forfactoring them in and developingnational industries.


Antiquity ◽  
1962 ◽  
Vol 36 (143) ◽  
pp. 206-209 ◽  
Author(s):  
D. L. Clarke ◽  
G. Connah

Recent work on Archaeomagnetism has been concentrated in two main fields, first, detection of sites with magnetic anomalies using instruments like the proton magnetometer, and secondly the construction of a dated graph of the earth’s magnetic field with the ultimate aim of providing an absolute chronology for fixed fired sites, mainly kilns and hearths. Important work in a third field, using the changing angle of inclination of pottery to provide a relative chronology for a series of vessels entirely independent of archaeological means, has fallen out of fashion despite the efforts of the pioneers of Archaeomagnetism and more recently the researches of Mr R. M. Cook on Corinthian pottery, at Cambridge and Dr M. J. Aitken on Chinese porcelain at Oxford. It is with this third method of approach that the present article is concerned and its application to a series of British beakers.When a clay vessel is fired its temperature is usually raised well above the Curie-point, about 500-600° C.; at this point the magnetic elements in the clay will begin to orientate themselves with the prevailing Earth’s magnetic field rather as though they were myriads of minute compass needles. Upon cooling, this uniform orientation will remain ‘fossilized’ and under normal conditions a permanent record of the Earth’s magnetic field at the time and place of firing. However, the finished vessel will then be used and removed from its firing position, thus for ever removing any chance of comparing its angle of declination (or compass bearing) with that now existing, since their positions relative to geographic north cannot be determined. If it can be shown that the vessel was fired in a vertical position the angle of inclination (dip) is still recoverable for comparison with the modern angle and with that preserved in other similar vessels. Since the angle of inclination alters a little every year (non-linearly)—it should be theoretically possible to arrange them in relative order of firing or date, thus providing an invaluable relative chronology.


Geophysics ◽  
1962 ◽  
Vol 27 (5) ◽  
pp. 627-650 ◽  
Author(s):  
Gordon D. Bath

In a study of the relationship of magnetic anomalies to the magnetite content and structure of layered Precambrian iron‐formations, the effective induced and remanent magnetizations of the Biwabik iron‐formation were determined by analyses of aeromagnetic anomalies recorded 1,000 ft above the Biwabik in areas of known geology. The induced magnetization along the layers is relatively insignificant because the formation is almost perpendicular to the earth’s magnetic field. For the relatively unmetamorphosed iron‐formation of the Main Mesabi district, the dominant magnetization was found to be across the layers, about 0.012 gauss, and most likely induced. For the strongly metamorphosed iron‐formation of the East Mesabi district, the dominant magnetization was found to be along the layers, about 0.100 gauss, and remanent. These values are used as bases for explaining aeromagnetic anomalies from correlatives of the Biwabik iron‐formation in the Gunflint, Cuyuna, and Gogebic districts.


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