The word “clays” was assigned early to fine grained material in geological formations (Agricola 1546) or soils (de Serres 1600). Clays have been identified as mineral species in the begining of the 19th century in the production of ceramic materials (Brongniart 1844). Then Ebelmen (1847) carefully analyzed the decomposition of rocks under chemical attack and the way that porcelain can be commonly made. Since this pionner works, the definition of clays has varied.

The reader probably is acquainted with some books of the series: Physics for Everybody, Chemistry for Everybody, Mechanics for Everybody, Algebra for Everybody, Geometry for Everybody and Arithmetic for Everybody. In the form of short stories, these books write of the interesting processes and phenomena that take place in nature, and describe unique mechanisms;

The idea of this brief chapter is to introduce students to the concept of fossil occurrences and their use, through geological time. An approach that defines the geological time scale, a method of relating the timing and relationship between events that have occurred during Earth’s history. The Geologic time is divisible into four Eons, Hadean, Archean, Proterozoic, and Phanerozoic (Fig. 1.1). The Eons are further divided into Eras; the Phanerozoic is divided into Paleozoic, Mesozoic, and Cenozoic (Fig. 1.1). The Eras are based on major changes in fossils record (such as extinction and origination; the latter is the appearance of new forms). The Eras are further divided into smaller units called Periods, in which a single type of rock system is formed; these are further divided into Epochs like the Paleogene is divisible into Paleocene, Eocene, and Oligocene (Fig. 1.1). However, in spite of a long impressive fossil record, it is also interrupted by major and minor extinction events (Fig. 1.1; see also Hart 1996; Hallam and Wignall 1997; Koeberl and MacLeod 2002; Taylor 2009). The Phanerozoic record of marine invertebrates, in particular, is interrupted by numerous, geologically short-term intervals (generally <3 Ma) during which biotic diversity and abundance declined significantly (<40 % at the familial level and <63 % at the generic level) (Raup and Sepkoski 1986) (see Fig. 1.1). Extinctions (major and minor) do not fall within the preview of this book but have only been mentioned to allude to the interruptions within the fossil record. <...>

Our natural, environmental home on planet Earth is a complex system of interacting components that includes climate and the atmosphere, organisms and their communities, water, landforms, and soils. The ways we choose to use and affect the environment today can benefit or endanger our own as well as future generations. More than ever before, people today want and need to know the effects of their actions on the environment at both a local and global scale.