What did Nicolaus Steno contribute to geology?

 

What did Nicolaus Steno contribute to geology?

Nicolaus Steno (Niels Stensen; 1638-1686) was a Danish geologist and anatomist. In  1669, he determined that the so called "tonguestones" sold on the Mediterranean island of Malta as good luck charms were actually fossilized sharks' teeth. He also developed what is cal1ed Steno's law, or the principle of superposition. This theory says that in any given rock layer, thebottom rocks are formed first and are the oldest. 

      Steno proposed two other principles: that rock layers are initially formed horizontally (often called the law of original horizonality), and that every rock outcrop in which only the edges are exposed can be explained by some process, such as erosion or earthquakes (often called the law of concealed stratification), All of these principles are generally held to be true today. Some people consider Steno to be the "father of modern geology," a title also given to several other early geologists, including James Hutton.