Paleogene (66-23 million years ago):
* Continental Drift: The continents continued to drift apart from the supercontinent Pangaea, leading to the formation of the Atlantic Ocean and the opening of the Tethys Sea. This movement caused major shifts in ocean currents and climates.
* Mountain Building: The Alpine-Himalayan mountain range began to form as the African and Indian tectonic plates collided with the Eurasian plate. This process significantly altered regional climates and drainage patterns.
* Climate: The early Paleogene was generally warm and humid, with a global average temperature several degrees higher than today. This led to the expansion of tropical and subtropical ecosystems. As the period progressed, temperatures cooled and glaciers began to form at the poles.
* Sea Level: Sea levels were generally higher than today due to the expansion of ocean basins and the lack of extensive polar ice sheets. This resulted in the inundation of many coastal areas and the formation of shallow seas.
Neogene (23-2.6 million years ago):
* Continued Continental Drift: The continents continued their northward drift, with North America and South America finally colliding to form the Isthmus of Panama. This had a profound impact on ocean currents and resulted in the separation of the Atlantic and Pacific Oceans.
* Mountain Building Continued: The Alpine-Himalayan mountain range continued to rise, with the Himalayas reaching their current elevation. This mountain range had a significant impact on regional climates, causing monsoon patterns in South Asia and creating the Tibetan Plateau.
* Cooling Climate: The Neogene saw a gradual cooling trend, leading to the expansion of glaciers at the poles and the development of ice ages. This cooling was driven by factors such as changes in atmospheric CO2 levels, continental drift, and the uplift of mountain ranges.
* Sea Level Fluctuations: Sea levels fluctuated throughout the Neogene, with periods of both high and low sea levels. These fluctuations were influenced by glacial cycles and tectonic activity.
Key Events and their Impact on Geography:
* Formation of the Isthmus of Panama: This event had a profound impact on global ocean circulation. It led to the formation of the Gulf Stream, which brought warm water northward, contributing to the warming of Western Europe.
* Rise of the Himalayas: This mountain range significantly altered regional climates, causing the development of the monsoon in South Asia and creating the Tibetan Plateau, the "Roof of the World."
* Ice Age Cycles: The onset of ice age cycles led to the expansion of glaciers and the lowering of sea levels. This resulted in the formation of land bridges, such as the Bering Land Bridge, which allowed for the migration of animals between continents.
Overall, the Tertiary period witnessed dramatic changes in Earth's geography, shaping the continents and oceans as we know them today. The movement of continents, the rise of mountains, and the fluctuating climate all played a significant role in creating the landscapes and ecosystems we see today.
