Fossil fuel embedded energy is still photosynthetic in origin. Terrestrial plants, on the other hand, tended to form coal and methane. Many of the coal fields date to the Carboniferous period of Earth's history. Terrestrial plants also form type III kerogen, a source of natural gas. There is a wide range of organic, or hydrocarbon, compounds in any given fuel mixture. The specific mixture of hydrocarbons gives a fuel its characteristic properties, such as boiling point, melting point, density, viscosity, etc. Some fuels like natural gas, for instance, contain only very low boiling, gaseous components. Others such as gasoline or diesel contain
Interlanguage fossilization particularly regarding achievement motivation, especially considering that fossilization can be considered the most distinctive characteristic of adult SLA. The text of this article is taken with permission from "The Role of Achievement Motivation on the Interlanguage Fossilization of Middle-Aged English-as-a-Second-Language Learners" by Dr. Zoran Vujisić (2007). Interlanguage fossilization Interlanguage fossilization is a phenomenon of second language acquisition (SLA) in which second language learners develop and retain a linguistic system, or interlanguage, that is self-contained and different from both the learner's first language and the target language. This linguistic system has been variously called interlanguage, approximative system, idiosyncratic dialects, or transitional