Cambrian-Ordovician Extinction

Thursday, June 14, 2012

During the Cambrian period, life flourished. The Edicaran life had remained largely unchanged for millions of years, but in the Cambrian it suddenly diversified and evolved into endless new forms. Exotic crustaceans and trilobites became the dominant life in their huge numbers and variety. Shellfish and giant aquatic arthropods, similar to insects, filled the seas. These creatures had rigid exoskeletons which left a bounty of fossils for us to study. Life flourished until, rather suddenly in geological terms, over 40% of all species suddenly became extinct 488 million years ago. Those that remained survived poorly at best due to some harsh change in the environment. What this change was we do not know. One theory is that a glaciation occurred, the coldest part of an ice age. We have been enjoying an interglacial period, the warmest part of an ice age, for the past eleven thousand years. An extreme change in temperature can easily cause the extinction of a huge amount of life. This extinction event marked the border between the Cambrian and Ordovician periods.


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