Overall I found this three-part documentary series to be very informative and eye-grabbing. With its many visual effects and transitions, it was quite easy to stay engaged which is usually hard for me during a documentary! To make this easier on the reader I figured I would separate my review into three parts with each one detailing a different section of the series.
Origins
The series is led by a man named Kirk Johnson and part one explores the origins of our continent by first going to our massive 300 mile-long Grand Canyon. The canyon and the rest of the American Southwest was originally all desert, with the different layers of the canyon spanning from 270 million years old to 515 million years old at the bottom. The top layer is sandstone and the bottom-most layer is granodiorite (with a limestone layer about 1000 meters down which signifies there used to be water here).
These layers of rock give us insight into the different biomes that enveloped this area throughout time, as shown by the image I screen capped from the episode. As I said earlier, this whole landscape was once underwater as viewed by the limestone layer filled with small fossils.
Another important topic Johnson covers in this episode is the origin of the actual continental crust (volcanoes). He travels to the shield volcano Mt. Kilauea, in Hawaii and shows us a forest that is doomed to be burned by a coming lava flow. Two rocks are shown, Basalt and Granite, one being found in our oceans and on islands such as Hawaii but the latter being the main composition rock that makes our continental crust.
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Life
The second part of this series delves into species and other organism’s history on our continent. What episode of life would be complete without delving into the life of dinosaurs? Johnson goes to Utah with his friend Joseph Sertich where they talk about a newly discovered carnivore called the Lythronax (King of Gore). Fun fact: Over a quarter of all fossils found worldwide, were found here in North America. 
To explore this connection between life and land, we fast forward to a spot in the Bahamas that houses some rare Stromatolites. Stromatolites are living rocks that under their surface, house thin coatings of bacteria. These bacteria build up microbes over time that layer in with mud and dirt to form these mound-like rocks that are Stromatolites. The reason they are so rare is due to their competition with modern-day seaweed and coral.
Jumping forward in the episode, Kirk travels to the Badlands of North Dakota where he searches for signs of a cataclysmic event that forever changed life on our continent and planet. After digging for some time, he finally finds the layer of white and rust that indicates two things: a massive eruption of volcanic events that shot glass beads into the sky and rained the earth, and shocked quartz which is only caused by quartz being put under an ENORMOUS amount of energy and pressure like during a nuclear explosion. Since there were no atomic bombs millions of years ago, the only explanation is a large asteroid slamming into the Earth.
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Human
The final entry in this documentary begins with ice. Johnson visits a giant glacier in Alaska and tells how our ancestors first spread from Africa through Europe and then Asia, but not the Americas because they were still in an Ice Age. Because of all of this frozen water, global sea levels dropped! This, in turn, revealed a land bridge between Siberia and Alaska that allowed people to eventually migrate here.
On Santa Rosa Island, off the coast of California, human remains were found that date back earlier than previous findings, almost 13,000 years! Since the remains were found on an island, this begs the question of boats and if so, they likely paddled along the coast of the frozen continent until they came across the island.
Fast forward to a more modern era, and the episode delves into the Transcontinental Railroad. Iron and Coal mines were a huge hit in the west in the 1860s and it sparked a revolution across the nation with the steam locomotive. With this new creation, the east and west coasts were destined to be connected but the Sierra Nevada mountains in the West posed a problem, the solution? Cut through them.
Most of the mountains were solid granite so the only viable options were explosives and hand tools, because of the sheer amount of manpower needed, Chinese laborers were a common hire. At the end of the project, a total of about 15 tunnels were ready to be used. It took about 15 months to finish and the two sides of the railroad met in Utah on May 10th, 1869. With the two coasts of the US linked, the economy soared to new heights, resulting in our greatest find ever: oil.
**All pictures and information are taken straight from the PBS documentary series with links attached below:
References:
Oceans Seven 