Sixteen years after his discovery, he published a geological map of England showing the rocks of different geologic time eras.Methods for relative dating were developed when geology first emerged as a natural science in the 18th century.Explanations: A – folded rock strata cut by a thrust fault; B – large intrusion (cutting through A); C – erosional angular unconformity (cutting off A & B) on which rock strata were deposited; D – volcanic dyke (cutting through A, B & C); E – even younger rock strata (overlying C & D); F – normal fault (cutting through A, B, C & E).The principle of cross-cutting relationships pertains to the formation of faults and the age of the sequences through which they cut.
In geology, when an igneous intrusion cuts across a formation of sedimentary rock, it can be determined that the igneous intrusion is younger than the sedimentary rock.
While digging the Somerset Coal Canal in southwest England, he found that fossils were always in the same order in the rock layers.
As he continued his job as a surveyor, he found the same patterns across England.
Geologists still use the following principles today as a means to provide information about geologic history and the timing of geologic events.
The principle of Uniformitarianism states that the geologic processes observed in operation that modify the Earth's crust at present have worked in much the same way over geologic time.