Later than that we run out of seafloor, so other ways have to be used, like paleomagnetic poles and fit of geological observations.

They would also "make geological and other observations".

Plate tectonics theory arose from two separate geological observations: seafloor spreading and continental drift.

Evidence for this includes geological observations, the longest instrumental records and the observed rate of 20th century sea level rise.

For example, geological observations indicate that during the last 2,000 years, sea level change was small, with an average rate of only 0.0-0.2 mm per year.

He created many careful studies of natural forms, based on his detailed botanical, geological and architectural observations.

Records of geological observations in all these districts were published by him.

They stayed there a month making astronomical, meteorological and geological observations.

He then travelled throughout Europe making geological observations, and was elected Fellow of the Royal Society in 1845.

His geological observations included a note that: