Important Steps in the Development of Geology…
1500 – Leonardo da Vinci:
- recognized fossil significance of shells in Italy and
suggested that they indicated different ages and origins.
1670 – Nicholas Steno:
- studied fossils and sedimentary rocks. He formulated
three main ideas about sedimentary rock layers:
“Steno’s Principles”:
A) Superposition: in a sequence of undisturbed rock layers,
the oldest is on the bottom.
B) Original Horizontality: all sedimentary rock layers are
originally formed in a horizontal position.
C) Lateral Continuity: sedimentary rock layers extend
laterally.
1750 – G.L. de Buffon:
- suggested six distinct epochs for earth’s history, and
questioned the literal significance of six days for the
biblical creation of the earth.
- He represents a major turning point in the history of
geological thought. He considered the earth to be very old,
and rejected “Catastrophism” – the idea that earth formed
only through catastrophes.
1780 – Georges de Cuvier Lavoisier:
- discovered the principles of fossil correlation
- Mapped the Paris sedimentary Basin
1800 – William “Strata” Smith:
- He was a civil engineer in England responsible for
mapping canals and coal mines. He is usually referred to
as the “Father of Field Geology”.
- Eventually he noticed that certain rock layers were similar,
and found in different parts of the country. He traced
similar beds based on rock types and fossil assemblages,
becoming the one of the first people to use fossil
correlations in geology.
T Webb – Horton High School, Wolfville, NS
Around the eighteen hundreds, geology was influenced by two major
theories – Neptunism and Plutonism.
Neptunism – Theory of Abraham G. Werner, first published in 1787. He
was a very influential speaker, and developed a wide following. This
theory regarded the earth as being much older than humans are. He
postulated that there was a universal ocean from which all rock types
precipitated (explaining the name “Neptunism” – god of the underwaters).
He suggested that there were four stages in earth’s history, based on four
changes in the sea level.
First sea level
Transition rocks
Second sea level
Secondary rocks
Third sea level
Tertiary rocks
Fourth sea level
(present)
Primitive or primary rocks
Plutonism: Theory of James Hutton (Scottish geologist). In 1795, he
published a book “Theory of the Earth with Proof and Illustrations”, and
this became the foundation of modern geology. Hutton proposed his
theory of uniformitarianism, stating that:
 The earth was very old, and not formed by catastrophes alone.
 The earth was a great internal heat machine (hence the name
“plutonism” – for Pluto, god of the underworld). Hutton was greatly
impressed with the role of volcanism in geology.
 The earth formed slowly, and those geological processes that we
observe today are the same as ones that occurred thousands of years
ago.
Charles Lyell (“Principles of Geology”) supported Hutton’s views. Lyell’s
book was considered to be the first definitive text on geology, with the
second edition published in 1830. He stated the principles of
uniformitarianism: geological events that are occurring today occurred
throughout geological history. This idea influenced Darwin and his
theories on evolution of the species…
T Webb – Horton High School, Wolfville, NS