How the Earth Was Made: DEADLY Wastelands & EXTREME Phenomena *3 Hour Marathon*

The Sahara Desert, known as the world's largest hot desert, has undergone dramatic changes over millions of years. Once covered by an ocean and home to freshwater lakes and vibrant ecosystems, evidence of marine fossils, ancient whale remains, and remnants of human settlements reveal a Sahara that was vastly different from the arid expanse we see today. These discoveries challenge our understanding of the desert's history, suggesting that it was once a lush, green landscape teeming with life. The transformation of the Sahara is attributed to shifts in the Earth's climate and tectonic movements, which gradually turned this once-thriving region into the desert we know today.

The Sahara Desert's transformation over time is marked by significant geological and climatic events. Fossils and geological formations provide clear evidence that the Sahara was once submerged under a vast sea, known as the Tethys Sea, which stretched across much of North Africa. The discovery of whale fossils and other marine life in the desert's valleys, alongside evidence of ancient lakes, points to a time when the Sahara was a lush, water-rich environment. This watery past, dating back 40 million years ago, was altered by the movement of the African tectonic plate, leading to the desertification of the Sahara and the emergence of its current landscape.

Approximately 20 million years ago, the Sahara Desert transitioned from a tropical swamp to a desert due to changes in the Earth's orbit and climate patterns. Despite becoming a desert belt region, the Sahara experienced periods of greening every 20,000 years, driven by shifts in monsoon patterns. These shifts led to the formation of giant freshwater lakes and rivers, transforming the desert into a habitable landscape for both humans and wildlife. Evidence of these green periods is found in fossils, cave paintings, and ancient settlements, highlighting the Sahara's dynamic climate history and its impact on human migration and evolution.

The Sahara's last green phase occurred around 7,000 years ago, marked by a thriving ecosystem supported by monsoon rains. However, geological evidence shows that this lush period ended abruptly within a few centuries, as the region returned to its desert state. The transition was so rapid that it significantly impacted the human populations living in the Sahara, forcing migrations and shaping the development of ancient civilizations such as Egypt. This dramatic change, captured in geological records and ancient cave art, underscores the Sahara's volatile climate history and its profound effect on human history.

Everest, the highest mountain on Earth, was formed through a series of geological processes involving the collision of the Indian and Eurasian tectonic plates. This monumental event, which began around 50 million years ago, pushed the ocean floor upwards, creating the Himalayan mountain range. The discovery of marine fossils at Everest's summit provides undeniable evidence that the mountain was once under the sea. The continuous movement of the Indian plate still contributes to Everest's growth, highlighting the dynamic nature of Earth's geology. The formation of Everest is a testament to the power of tectonic forces and their role in shaping our planet's landscape.

Over the past two million years, North America has been significantly shaped by the power of ice during various ice ages. Glaciers, extending over vast areas of the continent, sculpted the landscape, creating features such as the Great Lakes, Niagara Falls, and reshaping river courses like the Mississippi. The retreat of these ice sheets also led to the formation of distinct geological features and contributed to the distribution of fertile soils across the continent, profoundly influencing the natural environment and human settlement patterns. This historical interplay between ice and land underscores the enduring impact of glacial periods on North America's geography.

Gold, one of Earth's most cherished metals, was formed billions of years ago in the aftermath of supernova explosions. These cosmic events scattered gold atoms across the universe, eventually integrating them into the forming Earth. Despite its abundance, gold is mostly found in minute, dispersed particles within the Earth's crust. The quest for gold has led to various mining revolutions, from the early days of river panning in California and Australia to the extraction of gold from deep underground mines in South Africa, revealing the extensive efforts humanity has undertaken to uncover this precious metal. The ongoing exploration and technological advancements continue to unveil the mysteries of gold's formation and distribution.