Quick Fact: The Tertiary Period lasted roughly 63.4 million years, stretching from about 66 million years ago to 2.6 million years ago. It was a major chapter in Earth’s story, reshaping life and climate. These days, geologists split it into two parts: the Paleogene and Neogene.
Geographic Context
Imagine Earth halfway through its makeover. The Tertiary Period was that time—reptiles were fading out, mammals were taking over, and the continents were on the move. Africa, Eurasia, and the Americas started looking like the places we know now. Ecosystems shifted too, setting the stage for later species, including our distant relatives. (Honestly, this was one of Earth’s biggest makeovers.)
Key Details
| Aspect | Details |
|---|---|
| Duration | ~63.4 million years (66–2.6 million years ago) |
| Subdivisions | Paleogene (66–23 million years ago) and Neogene (23–2.6 million years ago) |
| Major Climate Shift | From hot and humid to cooler, ending in an Ice Age |
| Key Mammals | Early horses, mastodons, primates, whales, and carnivores like cats and dogs |
| Geological Event | K-T boundary extinction (66 million years ago), triggered by a meteorite impact |
| Continental Drift | Continents shifted toward modern positions, altering ocean currents and climates |
Interesting Background
Picture the scene: a meteorite hits, dinosaurs vanish, and suddenly mammals get their big break. That’s the Tertiary for you. By the Oligocene (~34–23 million years ago), grasslands spread as forests shrank, helping grazing animals like early horses thrive. Then came the Miocene (23–5.3 million years ago), when apes and early human ancestors like Australopithecus showed up. Volcanoes erupted, temperatures dropped, and by the Pliocene (5.3–2.6 million years ago), Earth was sliding into the Ice Age. (It wasn’t exactly a peaceful time.)
Practical Information
Our species, Homo sapiens, didn’t show up until roughly 300,000 years ago. But the Tertiary? That’s where the real prep work happened. Fossil hotspots like the Badlands of South Dakota (Miocene mammals) and Ashfall Fossil Beds in Nebraska (Pliocene mammals) hold clues. Geology buffs love these layers—they’re like a time machine for climate change. Want to see Tertiary fossils up close? The Smithsonian National Museum of Natural History has plenty, from early mammals to plants that shaped today’s world.
