Thermodynamics has played a major role in improving our understanding of natural processes and would continue to do so for the foreseeable future. In fact, a course in thermodynamics has now become a part of Geosciences curriculum in many Institutions despite the fact that a formal thermodynamics course is taught in every other department of physical sciences, and also in departments of Chemical Engineering, Materials Sciences, and Biological Sciences. The reason thermodynamics is taught in a variety of departments, probably more so than any other subject, is that its principles have wide ranging applications but the teaching of thermodynamics also needs special focus depending on the problems in a particular field. <...>

“Agate” is defined by the American Geological Institute Glossary (1960) “as a kind of silica consisting mainly of chalcedony in variegated bands or other patterns commonly occupying vugs in volcanic and some other rocks.” Dana’s Textbook of Mineralogy (1898) defines agate as “a variegated chalcedony. The colors are either (a) banded; or (b) irregularly clouded; or (c) due to visible impurities as in moss agate, which has brown moss-like or dendritic forms, as of manganese oxide, distributed through the mass.

The geometry and distribution of the clastic dv s.es of the Ono district. North Sacramento Valley are examined within stream sections. Five traverses along dry stream beds provide good exposure allowing the spacing, thickness and geometry of the dykes to be reorded. The spatial and thickness distribution of the dykes are considered using cumulative frequency plots, allowing a visual estimation of a best lit distribution. Dyke thickness conforms best to a log-normal distribution. There is also a characteristic minimum dyke thickness in a traverse and this is attributed lo the minimum aperture thai a fluid with sand clasts is able to exploit. Dyke spacing, however, shows a good correlation with a power-law distribution for four traverses, suggesting thai there is a mechanistic control on the spatial dislribulion. Plolting dyke thickness against minimum dyke spacing reveals that thin dykes do not generally intrude in isolation. I'nlike veins and igneous dykes, elastic dykes continue lo provide preferential pathways for fluid flow, subsequent lo their intrusion, thus inhibiting intrusion in the area surrounding a pre-existing dyke. Acombination of this process and dyke branching provides the best model for the observed spatial and thickness distribution of clastic dykes seen in the Ono district. California.