Historical Connections to Geology
Early understanding of geologic materials includes the Neolithic and Bronze Age mining of flint in Europe, and the mining of gold, copper, iron, and clay in the Middle East, as well as development of smelting techniques for producing metal tools and weapons by 4000 BC.
The Romans, Arabians, and Greeks all contributed to our understanding of the earth. Aristotle (384-322 BC) reflected on the meaning of fossils and the deposition of sediment, and realized that fossil seashells found in rocks were similar to those living creatures found on the beach, indicating that the fossils were once living organisms. Eratosthenes (250 BC) calculated the circumference of the Earth by measuring noontime shadows at two localities of different latitude. In 79 AD, Italian Pliny recorded the volcanic eruption of Vesuvius and the destruction of Pompeii.
In the early 1500’s, Leonardo da Vinci echoed Aristotle’s view when da Vinci recognized that fossils found in the sedimentary rocks in the mountains of northern Italy were the remains of shells from animals that once lived in the sea. James Ussher (1581-1665) was the first to estimate the age of the Earth using genealogies of the Bible. Ussher’s ~6,000 year old earth was widely accepted until the 18 th century. Nicholas Steno in 1669 gave us basic geologic principles explaining the nature of sedimentary rock layers which include the laws of: Superposition, Original Horizontality, and Concealed Stratification.
As a structured discipline of science, geology is relatively young compared to some of the other sciences. It emerged as a separate branch of science in the late 1700’s to early 1800’s. Important researchers of this period include Scottish James Hutton, and British Charles Lyell and William Smith. Hutton (1726-1797), who is regarded as the father of modern geology, recognized the importance of unconformities and developed the concept of uniformity of geologic processes which stated that the past history of Earth must be explained by the processes seen to be happening in the present. Charles Lyell (1779-1875) wrote the classic textbook, 'Principles of Geology' in 1830-1833 in which many basic principles of geology were recognized and described. He believed that each geological period perhaps lasted hundreds of millions and therefore the age of the Earth had to be much older. Englishman William Smith (1769-1839) established stratigraphic succession by determining that two rock layers from different sites can be regarded as similar in age if they contain the same fossils. In 1815 Smith preserved his place in history by constructing and publishing the first geologic map.
Geologic milestones in the early 1900’s include: Pierre and Marie Curie’s (1867-1934) discovery of radium (1898) which led to a new tool for absolute dating of certain rocks, Alfred Wegener’s (1912) proposal of the continental drift theory, and Harry Hess’s (1960) sea-floor spreading hypothesis which ushered in the modern theory of plate tectonics.
Today our understanding of earth continues to expand with the never ending development of new technologies. Geologists are discovering ways to “look” deeper into earth’s interior with the use of seismic tomography and to study earth’s surface features from afar using satellite remote sensing.