March 30, 2013

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March 30, 1759: The Four Layers of Earth

By David Bressan

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This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American

In a letter dated to March 30, 1759 the Italian mining engineer Giovanni Arduino (1714-1795) proposed to the physician and fossil collector Prof. Antonio Vallisnieri the subdivision of earth's crust in various classes of rocks.

Based on his observations along the foothills of the Alps, Arduino recognized a stratigraphic column with 4 classes: unstratified or poorly stratified rocks (or "Primary Rocks", survived into the 20th century as "Paleozoic"), stratified rocks ("Secondary Rocks", or "Mesozoic"), more recent, as yet unconsolidated, sediments ("Tertiary Rocks") and as own category volcanic rocks.

Fig.1. Arduino used this famous section of rocks exposed in the Val d´Agno to explain his classification scheme. The numbers refer to the thickness of the strata, the letters to the description in the accompanying text. The extremely tattered state of the original drawing suggests that Arduino demonstrated it repeatedly to the many naturalists who visited him (image in public domain).

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Bibliography:

VAI, G.B. (2007): A history of chronostratigraphy. Stratigraphy Vol.4 No. 2/3: 83-97

My name is David Bressan and I'm a freelance geologist working mainly in the Austroalpine crystalline rocks and the South Alpine Palaeozoic and Mesozoic cover-sediments in the Eastern Alps. I graduated with a project on Rock Glaciers dynamics and hydrology, this phase left a special interest for quaternary deposits and modern glacial environments. During my research on glaciers, studying old maps, photography and reports on the former extent of these features, I became interested in history, especially the development of geomorphologic and geological concepts by naturalists and geologists. Living in one of the key area for the history of geology, I combine field trips with the historic research done in these regions, accompanied by historic maps and depictions. I discuss broadly also general geological concepts, especially in glaciology, seismology, volcanology, palaeontology and the relationship of society and geology.

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