Gary sent in a cluster of links. For example, at www.space.com/lava-flows-earth-magnetic-field-reversal.html … which concerns magnetic pole flips and associated volcanism. We are informed the process was much slower then previously envisaged. To arrive at this conclusion they used data from fossil lava flows.
Related to this we have a post at https://archaeologynewsnetwork.blogspot.com/2019/08/a-rocky-relationship… … where a study in the journal Nature (August 2019) says that contrary to earlier studies on plate tectonics the process began as early as 2.5 billion years ago. To arrive at this conclusion they looked at globally distributed metamorphic rocks that have been formed over the last 3 billion years – at 500+ different locations. Metamorphic rocks have been buried and heated deep inside the Earth's crust. In the process they have been transformed into a new kind of rock (hence the terms meta and morphic). Geologists claim to be able to measure the depth and temperature at which metamorphic rocks formed – and therefore heat flow at different phases in the crust. Plate Tectonics, it is thought, influences heat flow. Therefore metamorphic rocks can be used to study the history of the process. A bit circular.