Answer:
Both the start and the end of the Triassic period is marked by some really interesting and important events. <u><em>Major events were:</em></u>
<em><u>1. The major extinction event </u></em>
<em><u>2. Splitting of Pangaea
</u></em>
<em><u>3. Expansion of animal life
</u></em>
<em><u>4. Massive change and rejuvenation (appearance of Mammals)</u></em>
Explanation:
The Triassic is a <em>geologic</em> <em>period</em> and system which took place 251 to 199 million years ago. The Triassic is the <em>first and shortest</em> period of the Mesozoic Era.
<u><em>1. The major extinction event
</em></u>
Triassic period (and the Mesozoic era) didn’t exactly have such a glorious start. <u>Violent volcanic eruptions, climate change, a fatal run-in with a comet/asteroid</u> had set off the extinction of more than <em>90% of Earth’s species.
</em>
<u><em>2. Splitting of Pangaea</em></u>
By the start of the Triassic, <em>Pangaea </em>was already formed as a <u>supercontinent shaped like a giant C.</u> Almost as soon as the supercontinent formed, it started cracking. By the end of the Triassic period, 199 million years ago, tectonic forces had started splitting the supercontinent in two <em>(Laurasia in the north and Gondwana in the south).</em> The ocean called Tethys filled the “C” and that’s how the splitting of Pangaea started. Interesting thing to know is that earlier failed attempts of splitting formed rift valleys in North America and Africa that are today very rich in the best preserved fossils of Triassic life.
<u><em>3. Expansion of animal life
</em></u>
There is a long list of animals that <u><em>existed or first appeared</em></u> in the Triassic period.
The oceans were filled with the <em>coiled-shelled ammonites, mollusks, and sea urchins</em> that survived the <u>Permian extinction </u>and were quickly diversifying. The first corals appeared! Although, some other reef-building organisms were already present.
Other amazing creatures were: dolphin-shaped ichthyosaurus, plesiosaurus, fish, ancient squid, phytoplankton (two of the major groups still in the ocean today first appeared), frogs, salamanders, crocodiles, turtles, snakes, pterosaurs (a group of flying reptiles), moss, ferns, spiders, scorpions, centipedes (thrived), grasshoppers (first appeared), etc. As I said, the list is very long.
<u><em>4. Massive change and rejuvenation (appearance of Mammals)
</em></u>
Last but definitely not least characteristic of the Triassic is that it was the time of tremendous change and rejuvenation. Life that survived the so-called <em>Great Dying</em> repopulated the planet and gave rise to new creatures, such as rodent-size mammals and the first dinosaurs.
<u><em>Perhaps the biggest changes came with the evolution of dinosaurs and the first mammals in the late Triassic, starting around 230 million years ago (Eozostrodon, Coelophysis, Plateosaurus) </em></u>
The Triassic <u>finished</u> in the same way it began. Something, perhaps a <em>volcanic belch or an asteroid collision</em> caused another mass extinction. Dinosaurs, however, survived and went on to dominate the Jurassic. And the rest is history. :)
