Paleomagnetism Flashcards

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Questions and Answers

What does paleomagnetism study?

Rock formation processes

Earth's ancient magnetism (correct)

Ancient climate changes

Volcanic activity

What do paleomagnetists do?

Collect samples of the rock and measure the preserved magnetic field.

What is Earth's magnetic field like?

It is very similar to that of a bar magnet and is dipolar.

What is latitude?

A way of describing how far a point is north or south of the equator. Signup and view all the answers

What is longitude?

A way of describing how far a point is east or west of the Prime Meridian. Signup and view all the answers

What is inclination in paleomagnetism?

The angle that the magnetic field makes with the horizontal. Signup and view all the answers

How does inclination change from the equator to the poles?

Inclination is zero at the equator and increases to 90 degrees at the poles. Signup and view all the answers

What is the relationship between latitude and inclination?

There is a clear relationship between the inclination at a point and the latitude. Signup and view all the answers

What is declination in paleomagnetism?

The horizontal angle made by the magnetic line of force preserved in the rock and the line of longitude. Signup and view all the answers

How does a rock preserve a magnetic field?

Tiny magnetized minerals align themselves with the magnetic lines of force when the rock cools. Signup and view all the answers

What type of information can we get from the paleomagnetism of rocks?

Rotation of the continent Signup and view all the answers

What is the Magnetic Pole and Geographic Pole?

The magnetic pole does not necessarily coincide exactly with the geographic pole but averages over time. Signup and view all the answers

How do we determine the former latitude of a continent?

By dating the rock and measuring its magnetic inclination. Signup and view all the answers

How do we know if a continent has rotated?

By measuring the declination of the paleomagnetism in rocks. Signup and view all the answers

What can paleomagnetism not tell us?

It cannot provide all the historical positions of a continent; only inclination measurements can constrain latitude. Signup and view all the answers

What do we determine from the alignment of magnetic poles?

The possible historical positions of continents. Signup and view all the answers

What is the Apparent Polar Wander Path?

The path made by several poles for a continent covering a span of ages. Signup and view all the answers

Study Notes

Paleomagnetism Overview

Paleomagnetism studies the ancient magnetic fields preserved in rocks, revealing the historical orientation of Earth’s magnetic field.
Certain minerals, like magnetite, in rocks align with the magnetic field at the time of their formation, effectively "locking in" this information.

Measuring Paleomagnetism

Paleomagnetists collect rock samples and use magnetometers to measure the direction and intensity of the preserved magnetic field.
This data helps decipher Earth's magnetic history and the movement of tectonic plates.

Earth's Magnetic Field

Resembles a bar magnet, exhibiting a dipolar nature with distinct North (N) and South (S) poles.
Magnetic filings align parallel to magnetic lines of force above a bar magnet.

Geographic Coordinates

Latitude indicates a point's distance north or south of the equator.
Longitude describes a point's distance east or west of the Prime Meridian, which runs through Greenwich, England.

Magnetic Field Characteristics

Inclination refers to the angle the magnetic field forms with the horizontal plane, varying with latitude.
At the equator, inclination is zero and gradually increases to 90 degrees at the poles.

Latitude and Inclination

A strong correlation exists between inclination at a location and that location's latitude.

Declination

Declination is the angle between the preserved magnetic field line and the lines of longitude.
Magnetic lines of force are parallel to the Earth's longitudinal lines when viewed from above.

Rock Magnetism Preservation

Rocks preserve magnetic fields when minerals like magnetite align with the magnetic lines of force upon cooling below their Curie temperature.

Information From Paleomagnetism

Latitude at the time of rock formation can be inferred from inclination measurements.
Declination helps determine if a continent has rotated since the rock formation.

Magnetic vs. Geographic Poles

Magnetic poles do not always align perfectly with geographic poles, but their average positions converge over thousands of years.

Determining Former Latitude

A rock formed near the equator keeps its low inclination; if the rock is dated, it indicates the continent's past location.

Identifying Continent Rotation

Differences in declination from measurements in different locations, such as Missouri, can indicate continental rotation.

Limitations of Paleomagnetism

Individual inclination measurements cannot fully determine a continent's past position; multiple measurements are needed for accuracy.
Apparent Polar Wander Paths illustrate the paths of magnetic poles over time, reflecting continental movements.

Alignment of Magnetic Poles

The alignment of magnetic poles and rock samples can suggest possible continental arrangements; discrepancies highlight misplacements.

Apparent Polar Wander Path

The trail formed by multiple magnetic poles for a continent over time, assisting in reconstructing its historical positions and movements.

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Description

Explore the fascinating field of paleomagnetism with these flashcards. Learn about how ancient magnetic fields are preserved in rocks and discover the techniques used by paleomagnetists to study them. Perfect for anyone interested in geology or Earth sciences.