Paleomagnetism
Introduction
Paleomagnetism is the study of the record of the Earth's magnetic field in rocks, sediment, or archeological materials. Certain minerals in rocks lock-in a record of the direction and intensity of the magnetic field when they form. This record provides information on the past behavior of Earth's magnetic field and the past location of tectonic plates. The record of geomagnetic reversals preserved in volcanic and sedimentary rock sequences (magnetostratigraphy) provides a time-scale that is used as a geochronologic tool. Geophysicists who specialize in paleomagnetism are called paleomagnetists.
Principles of Paleomagnetism
Paleomagnetism relies on three key principles, which are remanent magnetization, magnetic domains, and magnetization processes.
Remanent Magnetization
Remanent magnetization, also known as paleomagnetism, is the magnetization left behind in certain types of rock and sediment after the Earth's magnetic field has changed. This remanent magnetization can be used to determine the past orientation and intensity of the Earth's magnetic field, providing valuable information about the Earth's geological history and the processes that have shaped it.
Magnetic Domains
Magnetic domains are regions within a material in which the magnetic moments of the atoms are aligned. In certain types of rock and sediment, these domains can become locked in place, preserving a record of the Earth's magnetic field at the time the rock or sediment was formed. This is known as magnetism.
Magnetization Processes
There are several processes by which rocks and sediments can become magnetized, including thermoremanent magnetization (TRM), detrital remanent magnetization (DRM), and chemical remanent magnetization (CRM). These processes involve changes in temperature, the movement of particles, and chemical reactions, respectively.
History of Paleomagnetism
The history of paleomagnetism dates back to the first observations of magnetism in rocks in the early 19th century. However, it was not until the 20th century that the principles of paleomagnetism began to be widely applied in the field of geology and geophysics.
Early Observations
The first observations of magnetism in rocks were made in the early 19th century by explorers and scientists such as Alexander von Humboldt and Louis Néel. These early observations laid the groundwork for the development of the field of paleomagnetism.
Development of Paleomagnetism
The field of paleomagnetism began to develop in earnest in the early 20th century, with the work of scientists such as Motonori Matuyama and Bernard Brunhes. These scientists made key discoveries about the Earth's magnetic field and its changes over time, paving the way for the use of paleomagnetism as a tool in geology and geophysics.
Modern Paleomagnetism
In the late 20th and early 21st centuries, paleomagnetism has become a key tool in the study of the Earth's geological history. It has been used to provide evidence for the theory of plate tectonics, to date geological and archaeological materials, and to study the behavior of the Earth's magnetic field over time.
Applications of Paleomagnetism
Paleomagnetism has a wide range of applications in the fields of geology, geophysics, and archaeology.
Geology
In geology, paleomagnetism is used to study the movement and orientation of tectonic plates over time. This can provide valuable information about the Earth's geological history and the processes that have shaped it.
Geophysics
In geophysics, paleomagnetism is used to study the Earth's magnetic field and its changes over time. This can provide valuable information about the behavior of the Earth's magnetic field and the processes that generate it.
Archaeology
In archaeology, paleomagnetism is used to date archaeological materials and to study past human behavior. This can provide valuable information about the history of human civilization and the development of human cultures.
Conclusion
Paleomagnetism is a valuable tool in the study of the Earth's geological history and the behavior of its magnetic field. By studying the remanent magnetization in rocks and sediments, scientists can gain valuable insights into the past orientation and intensity of the Earth's magnetic field, the movement and orientation of tectonic plates, and the history of human civilization.