Summary:
- Around 445 million years ago, the Earth experienced a global freeze, known as the Ordovician-Silurian mass extinction event.
- This dramatic climate change caused a significant drop in global temperatures, leading to the extinction of many marine species, including trilobites, brachiopods, and graptolites.
- The global freeze was likely caused by a combination of factors, including volcanic activity, changes in ocean circulation, and the formation of new mountain ranges, which disrupted the planet's climate system.