1. A compass is corrected for the difference between the magnetic North and geog
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Question
1. A compass is corrected for the difference between the magnetic North and geographic North pole using a parameter called 2. The temperature at which a rock locks-in a paleomagnetic signature is the temperature; the analogous temperature in geochronology is the temperature. 3. Decay by emission of a helium nucleus is 4. The curve, in the U-Pb system, that shows the idea co-evolution of 238U and 235U is called: 5. The lithospheric field contribution to the total field and secular variations have similar magnitudes of approximately nT and nT/a. 6. A time period when the Dipole component of the Earth's magnetic field weakens and the multi-pole components become stronger is called 7. Paleomagnetism captured by cooling of an igneous rock is called: 8. The total magnetic field at Queen's has a magnitude of approximately nT. 9. An Ar-Ar geochron age for a recent rock contradicts clear field relationships Assuming the field relationships are correct, three possible causes are: and 10. The Rb-Sr system commonly dates the mineral (name 1) and the Rb substitutes forExplanation / Answer
1) Magnetic declination.
Magnetic declination is the angle on the horizontal plane between magnetic north and true north, this angle varies with the position on the earth surface, and declination is positive when magnetic north is east of true north, and negative when it is to the west.
2) a) Curie temperature : is the temperatureat which certain materials lose their permanent magnetic properties, to be replaced by induced magnetism.
b)closure temperature: closure temperature is the thetemperature at which a system has cooled so that there is no longer any significant diffusion of the parent or daughter isotopes out of the system and into the external environment
3)Alpha decay.
Alpha decay (-(decay) is a type of radioactive decay in which an atomic nucleus emits an alpha particle (helium nucleus).and thereby transforms into an atom with a mass number that is reduced by four and an atomic number that is reduced by two.
4)Chronology
is the science of arranging events in their order of occurrence in time. the use of a timeline or sequence of events. It is also the determination of the actual temporal sequence of past events.
5)a)16-45nT (Lithospheric magnetic field)
magnetic field we measure at the earth's surface includes the contribution from the Earth's lithosphere and crust, both from induced magnetisation from the main field, and also permanent remnant magnetisation.
b)secular variation: 45nT/a
changes in the Earth's magnetic field on time scales of about a year or more. These changes mostly reflect changes in the Earth's interior, ie, changes in the convection of molten iron core.
6)Pole reversal
geomagnetic reversal is a change in a planet's magnetic field such that the positions of magnetic north and magnetic south are interchanged, while geographic north and geographic south remain the same. Earth's magnetic field is generated by dynamo action in which convection of molten iron core generates electric currents which give rise to magnetic fields.
7)thermo-remanent magnetism.
when magnetic minerals in igneous rocks cool through the Curie point and when the magnetic domains within the individual minerals align with the Earth’s magnetic field, thus making a permanent record of its orientation.
8)54000nT.
The dipole component of Earth's field can diminish even while the total magnetic field remains the same or increases, value of magnetic field on earth's surface ranges from 25000 to 65000nT
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