>> The positions of the continents were not only very different in the Mesozoic, but the climate was very different than it is today too. Overall, the temperatures were much higher and we even find dinosaurs in the polar regions. This is one of the best dinosaurs known from Antarctica. And this is the head of a dinosaur called Cryolophosaurus, which means frozen crested lizard. Now, the front of the skull is missing, but the skull is still attached to the neck. So we can see the back of the skull where it attaches to the neck. We can also see the eyes and the backs of the lower jaw. What's unusual about Cryolophosaurus is that it has a crest. And this crest in front of the eyes has a very unusual appearance because it's very tall. But also when you look at it from the front, it kind of looks like a, a snow shovel that's turned upside down on top of its head. And no other dinosaur has a crest like that. This is unique for this dinosaur from Antarctica. One might wonder how dinosaurs like this could survive in Antarctica even though it was millions of years ago. But at that time of course, there was no glaciers. There was probably not even any snow because it was 15 degrees Celsius warmer than it is today on average. We do find lots of evidence to support the warmer. Temperatures, including fossil plants. And interestingly enough, the first fossil plants were found by Robert Falcon Scott on his expedition to the South Pole nearly a century ago. And he recovered about 20 kilograms of fossil plants. That went to the South Pole and worked their way almost back to the base camp, when unfortunately the expedition perished from lack of food and the cold. The rescue team that went to recover Scott's frozen remains found the fossils and brought them back. >> Why would the climate of Antarctica have been so much warmer during the distant past? There may be more than one right answer, so check all that you think are correct. Was it closer to the equator? Was there a higher sea level? Or was there an altered ocean circulation? The climate in Antarctica was warmer for a number of reasons, including very different ocean currents, which transported warm water from the equator down to the polar region. Antarctica has actually been close to its current position for hundreds of millions of years. And though a higher sea level may have increased temperatures a bit, it is mainly ocean circulation patterns that contributed to Antarctica's ancient warm climate. So C is the correct answer. >> Part of the reason for this greatly increased temperature was the position of the continents. For example, today, a strong current encircles much of Antarctica. And this current tends to keep Antarctica relatively cold. However, 70 million years ago, when Antarctica was still attached to Australia. This current had to go up and around Australia. As the current moves through more equatorial areas, it would have become warmer and then, as it moved back down, carried this heat around and back to Antarctica. Ocean currents are extremely important to distributing and moving heat from one part of the Earth to another. Today, the gulf stream, a current composed of warm water that flows from the Gulf of Mexico up towards Europe, accomplishes just this task. Water is warmed in the Gulf of Mexico and flows towards the western coast of Europe making many European countries much warmer than places on the other side of the Atlantic at similar latitudes. One of the other reasons that the climate was much warmer had to do with sea level. >> In rocks from the late cretaceous, we see large numbers of fossils from sea animals, like ammonites and marine reptiles, across the interior plains of North America. Why do you think these fossils are preserved here? Were they deposited by Cretaceous hurricanes, deposited in large seaways, or transported by shifting continents? See level was much higher during the mesozoic era. Areas that are dry land today, were covered by vast, shallows seas back then. Although shift in continents have thrust some marine fossils into the mountains. And we have possible evidence of massive, ancient hurricanes. The marine fossils we find throughout central North America today, died in the seas they lived in. So, B is the correct answer. >> During the Cretaceous, sea level was much higher than today. Mainly due to three reasons: no glaciers, thermal expansion and increased mid-oceanic vulcanism. First, because there were no ice caps at this time, this increased sea level considerably. If all the ice caps melted today, sea level would rise by about 70 or 80 meters [INAUDIBLE]. Second, water will expand as it becomes heated. This is referred to as thermal expansion, and you can see a similar thing when you boil water in a kettle and the water overflows. As the waters get warmer. Sea level rises. [SOUND] Lastly. Sea floor spreading associated with plate tectonism can cause the ocean basins themselves to become shallower. Because the surface of the Earth, and the amount of water on it is fixed, if those basins fill up with rock and sediment, the water flows over the edges of the basin, and floods the land. [NOISE] If sea levels rose, how would that affect the amount of land on earth? Would land area increase or decrease? Land area decreases as sea level rises. Today, low-lying countries like the Seychelles. Could be entirely flooded if sea level rises by just a few meters. So, b is the correct answer. >> Although places like the Seychelles are in danger of going underwater if sea level rises even just a few meters, we know that sea levels have changed much more dramatically through geologic history. During the Mesozoic, sea levels were up to 250 meters higher than they are today. The most pronounced effect of this was the flooding of vast regions of the Earth, limiting the amount of exposed land, and splitting areas that are now connected into isolated islands. For example, if we look back to our maps that we had of the late Cretaceous. You can see that much of the interior of North America was flooded by a massive inland seaway. This seaway formed a continuous waterway that ran from the arctic ocean to the gulf of Mexico. >> What kind of effects do nearby lakes and oceans have on the land? More than answer may be correct so check all that apply. Is it increase precipitation? Decreased temperature? Or increased seasonality? A is the correct answer. In general, lakes and oceans make nearby lands wetter. They don't necessarily make temperatures cooler. But rather smooth out the extremes in temperatures. So that the summer highs and winter lows are closer together. Decreasing the seasonality. >> These shallow seas would have helped us smooth out temperature fluctuations throughout the year. Think about coastal cities compared to those more inland. Coastal cities typically have less extreme temperatures than those farther from water. Because, the water acts as a heat sync. During hot days, the water warms more slowly than land, keeping the nearby areas somewhat cooler. During winter, the water retains more heat for longer, keeping temperatures on nearby coasts higher. Along with this these flooded areas mean that there are more shallow water areas. Shallow water tends to lead to more evaporation, leading to more water vapor in the air. Water vapor is actually a more powerful greenhouse gas than carbon dioxide, raising temperatures even more. >> How would higher, more stable temperatures, and a higher sea level impact dinosaur biodiversity? Do you think these two things would have increased or decreased the number of dinosaur species? Higher temperatures and sea levels, meaning, fewer land connections and more isolated areas could've increased species diversity. These conditions would've increased the number of different types of dinosaurs. So A is the correct answer. >> But the very different climate and higher sea level likely contributed to the amazing success of the dinosaurs. In general, higher temperatures seem to cause species diversity. That is, the total number of species in an area, to increase. As well, because the higher sea level isolated terrestrial dinosaur populations from one another. These populations could've diverged from one another, again increasing species diversity. Although dinosaurs were undoubtedly successful, and still are. It was a combination of many factors, including both climate and geography, and not just their own biological adaptations, that led to their amazing diversity.
