Paleomagnetism as a means of dating geological events

12-Nov-2019 11:41

Correlation techniques are locally useful and depend on recognition of an event whose age is known, such as a volcanic eruption or a paleomagnetic reversal.

Geologic studies of active tectonism are greatly aided by definition and time calibration of local stratigraphic sequences.

Paleomagnetism is possible because some of the minerals that make up rocks—notably magnetite—become permanently magnetized parallel to the earth's magnetic field at the time of their formation.

Rocks from hot liquid magma (see lava), or even minerals made up of crystals that grow at low temperatures, can acquire magnetization.

A relative age is the age of a fossil organism, rock, or geologic feature or event defined relative to other organisms, rocks, or features or events rather than in terms of years.

Tradition paleontological and biostratigraphic correlation methods are still perhaps the most common relative dating methods used by geologists.

The cause of these magnetic "flip-flops" is not clearly understood.

Relative-dating techniques are nearly always applicable but are not precise and require calibration.Paleomagnetic studies of rocks and ocean sediment have demonstrated that the orientation of the earth's magnetic field has frequently alternated over geologic time.Periods of "normal" polarity (i.e., when the north-seeking end of the compass needle points toward the present north magnetic pole, as it does today) have alternated with periods of "reversed" polarity (when the north-seeking end of the compass needle points southward).More modern correlation technologies include use of marine stable isotope records, paleomagnetic dating, tephrachronology, geomorphological methods, sedimentation characteristics, and other geochemical and radiometric methods.Relatively young deposits can be sometimes dated using tree rings, varved-lake sediments, coral growth patterns, and other methods.

Relative-dating techniques are nearly always applicable but are not precise and require calibration.Paleomagnetic studies of rocks and ocean sediment have demonstrated that the orientation of the earth's magnetic field has frequently alternated over geologic time.Periods of "normal" polarity (i.e., when the north-seeking end of the compass needle points toward the present north magnetic pole, as it does today) have alternated with periods of "reversed" polarity (when the north-seeking end of the compass needle points southward).More modern correlation technologies include use of marine stable isotope records, paleomagnetic dating, tephrachronology, geomorphological methods, sedimentation characteristics, and other geochemical and radiometric methods.Relatively young deposits can be sometimes dated using tree rings, varved-lake sediments, coral growth patterns, and other methods.These break down over time in a process scientists call radioactive decay.