Igneous petrology Igneous petrology Igneous petrology is the study of igneous rocks—those that are formed from magma. As a branch of geology, igneous petrology is closely related to volcanology, tectonophysics, and petrology in general. The modern study of igneous rocks utilizes a number of techniques, some of them developed in the fields of chemistry, physics, or other earth sciences. Petrography, crystallography, and isotopic studies are common methods used in igneous petrology. The composition of igneous rocks and minerals can be determined via a variety of methods of varying ease, cost, and complexity. The simplest method is observation of hand samples with the
What Is the Third Estate? What Is the Third Estate? What Is the Third Estate? () is a political pamphlet written in January 1789, shortly before the outbreak of the French Revolution, by the French thinker and clergyman Abbé Emmanuel Joseph Sieyès (1748–1836). The pamphlet was Sieyès' response to finance minister Jacques Necker's invitation for writers to state how they thought the Estates-General should be organized. In the pamphlet, Sieyès argues that the third estate – the common people of France – constituted a complete nation within itself and had no need of the "dead weight" of the two other orders, the first and second