If Earth's magnetic field was fixed without reversals, newly-formed seafloor basalts would only show one magnetic orientation. This uniformity would make it harder to track the movement of tectonic plates or determine the age of the seafloor using magnetic stripes. It would also impact our understanding of plate tectonics and Earth's geology.
If Earth's magnetic field was fixed in place and did not reverse polarity, seafloor basalts would display a consistent magnetic orientation, making it more challenging to track long-term changes in Earth's magnetic field. This could impact our ability to study plate tectonics, as we rely on changes in magnetic polarity recorded in seafloor basalts to understand the movement of tectonic plates over time.
Lawrence W. Morley, Frederick John Vine, and Drummond Hoyle Matthews were the first to tie magnetic stripe anomalies to seafloor spreading. The magnetic anomalies was the first evidence that supported the theory of seafloor spreading.
Alluvial conglomerate rocks do not typically record the magnetic field at the time of their formation. These types of rocks are formed by the deposition of sediment particles in a river or stream, and their magnetic properties are often overprinted by later geological processes. To study ancient magnetic fields, scientists usually analyze igneous rocks like basalts or volcanic ashes.
== == Some basalts may be older than some sandstones, but ages of sandstones and basalts vary tremendously. Some sandstones are therefore older than some basalts. Oceanic basalts are rarely over 200 million years in age.
Pieces of evidence for sea floor spreading include the presence of mid-ocean ridges where new crust is formed, symmetric magnetic striping on either side of mid-ocean ridges, age dating of oceanic crust that shows it gets older as it moves away from ridges, and the discovery of pillow basalts and other volcanic rocks on the ocean floor.
If Earth's magnetic field was fixed in place and did not reverse polarity, seafloor basalts would display a consistent magnetic orientation, making it more challenging to track long-term changes in Earth's magnetic field. This could impact our ability to study plate tectonics, as we rely on changes in magnetic polarity recorded in seafloor basalts to understand the movement of tectonic plates over time.
Lawrence W. Morley, Frederick John Vine, and Drummond Hoyle Matthews were the first to tie magnetic stripe anomalies to seafloor spreading. The magnetic anomalies was the first evidence that supported the theory of seafloor spreading.
Basalts
Heat flow studies of the seafloor suggest that basalts within the oceanic crust take millions of years to completely cool as they continue to support passive hydrothermal circulation systems.
There is a mid ocean ridge that forms because the hot magma is lighter (less dense than the colder magma. The ridge is located at the spreading center. There are magnetic anomalies that can be thought of as stripes that mirror each other on either side of the spreading center. There are remnants of the pipes that form from upwelling hot springs (black smokers). There are pillow basalts that form from sudden cooling as it encounters sea water. It is generally rugged and rocky near the spreading center but tends to be more covered with sediments as you move away from it.
When magma reaches the surface of the ocean floor, it cools and solidifies to form igneous rocks like basalt. The rapid cooling of magma at the surface allows for the formation of characteristic features like pillow basalts and seafloor spreading ridges. Over time, these rocks may become buried, eroded, or further altered by geologic processes.
flood basalts and volcanoes
A factor that determines crystal size in igneous rocks is the speed in which the lava/ magma crystallised or froze. As pillow basalts form at mid ocean ridges where magma is erupted into direct contact with the cold sea water the crystals form very fast and are therefore small. Other basalts erupted on land still have relatively small crystals and crystallised relatively fast but overall slower then pillow basalts.
Alluvial conglomerate rocks do not typically record the magnetic field at the time of their formation. These types of rocks are formed by the deposition of sediment particles in a river or stream, and their magnetic properties are often overprinted by later geological processes. To study ancient magnetic fields, scientists usually analyze igneous rocks like basalts or volcanic ashes.
There is a 'striping' effect where magnetic material on the seafloor is aligned in different directions. "...during the upheaval of the Flood the flow of the molten iron in convection cells in the outer core carrying the freely-decaying electric currents meant that the resultant geomagnetic field generated would have rapidly changed direction and reversed its polarity because of that fluid movement. On the sea floor at the earth's surface new basalt lava flows were erupting rapidly due to the rifting apart of the old pre-Flood ocean floor and mantle plumes in mantle convection cells rising as a result of the catastrophic plate tectonics during the Flood. Each new basalt lava flow recorded the polarity direction of the geomagnetic field at the time it cooled. So due to the geomagnetic field reversing rapidly, and the basalt lava flows being erupted rapidly, the result was that these geomagnetic field polarity reversals were recorded in these sea floor basalts, both laterally and vertically. This paleomagnetic "striping" within the sea floor basalts was one of the key pieces of evidence that convinced geologists that the sea floor plates had spread, pushing the continental plates with them, albeit at a drift pace within their uniformitarian paradigm. However, Humphreys was able to demonstrate that because the paleomagnetic recordings of the polarity reversals were often in patches within the basalt sea floor and even within individual basalt flows, the reversals having occurred rapidly within days was a better explanation. The catastrophic plate tectonics model for the geology of the Flood thus provided a better context to explain the geomagnetic field polarity reversals. Thus Humphreys had even predicted that evidence of rapid reversals would be found before Coe, Prévot and their colleagues announced their discoveries, which of course then provided confirmation of both the Humphreys geomagnetic field model and the catastrophic plate tectonics model of the Flood. Source: AnswersInGenesis dot org article entitled 'More Evidence of Rapid Geomagnetic Reversals Confirms a Young Earth' (The above quote comes from the 14th paragraph).
basalts
flood basalts and volcanoes