Jurassic
The Jurassic period is a significant geological time scale division within the Mesozoic Era, spanning from about 201.3 million years ago to approximately 145 million years ago. This period is notable for:
- Flora and Fauna: During the Jurassic, the Earth experienced a proliferation of dinosaurs. Iconic genera such as Stegosaurus, Allosaurus, and Brachiosaurus roamed the landscapes. The period also saw the rise of pterosaurs and the early ancestors of mammals.
- Climate and Environment: The climate was generally warm with no polar ice caps, leading to vast interior seas and a landscape dotted with conifers, ferns, cycads, and ginkgoes.
- Geological Events: The Pangaea supercontinent began to break apart, leading to the formation of new continents and the expansion of shallow seas which facilitated the spread of marine life.
- Mass Extinctions: The Jurassic saw at least two major extinction events, though less severe than the ones marking the boundaries of other geological periods. These events affected marine life significantly.
- Human Impact: No humans existed during this period, but the Jurassic has had a profound impact on human culture, particularly through popular culture in movies like the Jurassic Park series.
Historical Context
The term "Jurassic" was coined by Alexandre Brongniart and Georges Cuvier in the early 19th century, derived from the Jura Mountains where many Jurassic rock formations are exposed. This period is divided into three epochs:
- Early Jurassic (Lias)
- Middle Jurassic (Dogger)
- Late Jurassic (Malm)
Stratigraphy
The Jurassic layers are known for their distinct rock formations, which are crucial for understanding the Earth's geological history. They include:
- Marine limestones and shales
- Coal deposits
- Oolitic limestone
References
External links for further reading:
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