Cretaceous Period; Geological period, final period of the Mesozoic Era Length: ~79 million years Time Span: ~145-66 million years ago.
References
Major Extinction Event
The World during this Time
Fun Facts Part 3
Fun Facts Part 1
Fun Facts Part 2
Interesting Facts Part 1:
Here is an image of the late cretaceous, about 94 million years ago. The Cretaceous saw the highest sea levels in Earth's timeline. Shallow seas covered much of North America and Europe.
In the Cretaceous Period, some of the largest dinosaurs ever lived during this time. For example, the Argentinosaurus, which was capable of being over 100 feet long, was a sauropod existing during this period.
Interesting Facts Part 3:
Pterosaurs, which are flying reptiles, were extremely large avian species. For example, the Quetzalcoatlus had wingspans estimated to be between 10 and 12 meters. Here is a depiction of the pterosaur.
Here is a depiction of smaller mammals in the Cretaceous Period. Most mammals by the end of the Cretaceous were no larger than a raccoon in modern time. The ability of smaller mammals to burrow, be capable of varied diets, and being able to function in darkness helped them to endure the "nuclear winter" effect dropped by the asteroid impact which caused dust to block sunlight. This set the stage for the "Age of Mammals" after the Cretaceous Period.
References: APA Style
Longrich, N. R., Tokaryk, T., & Field, D. J. (2011). Mass extinction of birds at the Cretaceous–Paleogene (K–Pg) boundary. PLoS Biology, 9(3), e1001098. https://doi.org/10.1371/journal.pbio.1001098 Witts, J. D., et al. (2018). The impact of the Cretaceous–Paleogene (K–Pg) mass extinction on the global carbon cycle. Palaeogeography, Palaeoclimatology, Palaeoecology, 493, 1–12. https://doi.org/10.1016/j.palaeo.2017.11.033 “K–T extinction | Overview & Facts.” Britannica. Retrieved from https://www.britannica.com/science/K-T-extinction Montano, D., et al. (2023). A Lacustrine Record for the Cretaceous–Paleogene transition. Geosciences, 13(8), 227. https://doi.org/10.3390/geosciences13080227
The World During This Time
The climate was significantly warmer than today's time, with a notable zero polar ice caps. The sea levels were higher, and large parts of continents were covered with shallow seas. The atmosphere was rich in carbon dioxide, which made plant life full and lush. Angiosperms, or flowering plants, spread rapidly and changed ecosystems as well as sustaining new insect species. Birds and mammals diversified, although their similarities to dinosaurs made them comparable.
Dinosaurs ruled the Earth, with infamous species such as the Tyrannosaurus Rex, triceratops, and velociraptor.
Oceans were full of enormous marine reptiles such as the mosasaur and plesiosaurs, as well as the beginning of modern day sharks.
Interesting Facts Part 2:
Here is an image of a chalk deposit. The Cretaceous Period's name comes from the Latin word "Creta", which is the latin word for chalk. This was used because during this timeframe, there were massive chalk deposits.
Here is a depiction of Antartica during the Cretaceous Period. Antartica was covered in forests rather than ice. Fossilized tree trunks and dinosaurs have been excavated there in modern time.
Major Event: The Cretaceous-Paleogene Extinction Event
This extinction event ended the Cretaceous period about 66 million years ago. A plausible theory is that this happened by way of a ginormous asteroid. It was estimated to be 6 miles wide and it struck near present-time Yucatán, Mexico. This is also what formed the Chicxulub crater. The impact was devastating, it formed firestorms, earthquakes, tsunamis, and an almost "nuclear winter" effect, which entails dust entering the atmosphere and blocking sunlight. The event wiped out around 75% of life on Earth. Most dinosaurs were wiped off the planet, but this allowed certain mammals and birds to excel afterward.
Here is a depiction of the asteroid impact.
Most life on Earth was wiped off the planet. Many species were lost and became extinct. Both land animals, such as Tyrannosaurus Rex, and marine life, such as mosasaurs, all left the face of the planet.
Cretaceous Period; Geological period, final period of the Mesozoic Era Length: ~79 million years Time Span: ~145-66 million years ago.
Neil Prisco
Created on September 26, 2025
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Transcript
Cretaceous Period; Geological period, final period of the Mesozoic Era Length: ~79 million years Time Span: ~145-66 million years ago.
References
Major Extinction Event
The World during this Time
Fun Facts Part 3
Fun Facts Part 1
Fun Facts Part 2
Interesting Facts Part 1:
Here is an image of the late cretaceous, about 94 million years ago. The Cretaceous saw the highest sea levels in Earth's timeline. Shallow seas covered much of North America and Europe.
In the Cretaceous Period, some of the largest dinosaurs ever lived during this time. For example, the Argentinosaurus, which was capable of being over 100 feet long, was a sauropod existing during this period.
Interesting Facts Part 3:
Pterosaurs, which are flying reptiles, were extremely large avian species. For example, the Quetzalcoatlus had wingspans estimated to be between 10 and 12 meters. Here is a depiction of the pterosaur.
Here is a depiction of smaller mammals in the Cretaceous Period. Most mammals by the end of the Cretaceous were no larger than a raccoon in modern time. The ability of smaller mammals to burrow, be capable of varied diets, and being able to function in darkness helped them to endure the "nuclear winter" effect dropped by the asteroid impact which caused dust to block sunlight. This set the stage for the "Age of Mammals" after the Cretaceous Period.
References: APA Style
Longrich, N. R., Tokaryk, T., & Field, D. J. (2011). Mass extinction of birds at the Cretaceous–Paleogene (K–Pg) boundary. PLoS Biology, 9(3), e1001098. https://doi.org/10.1371/journal.pbio.1001098 Witts, J. D., et al. (2018). The impact of the Cretaceous–Paleogene (K–Pg) mass extinction on the global carbon cycle. Palaeogeography, Palaeoclimatology, Palaeoecology, 493, 1–12. https://doi.org/10.1016/j.palaeo.2017.11.033 “K–T extinction | Overview & Facts.” Britannica. Retrieved from https://www.britannica.com/science/K-T-extinction Montano, D., et al. (2023). A Lacustrine Record for the Cretaceous–Paleogene transition. Geosciences, 13(8), 227. https://doi.org/10.3390/geosciences13080227
The World During This Time
The climate was significantly warmer than today's time, with a notable zero polar ice caps. The sea levels were higher, and large parts of continents were covered with shallow seas. The atmosphere was rich in carbon dioxide, which made plant life full and lush. Angiosperms, or flowering plants, spread rapidly and changed ecosystems as well as sustaining new insect species. Birds and mammals diversified, although their similarities to dinosaurs made them comparable.
Dinosaurs ruled the Earth, with infamous species such as the Tyrannosaurus Rex, triceratops, and velociraptor.
Oceans were full of enormous marine reptiles such as the mosasaur and plesiosaurs, as well as the beginning of modern day sharks.
Interesting Facts Part 2:
Here is an image of a chalk deposit. The Cretaceous Period's name comes from the Latin word "Creta", which is the latin word for chalk. This was used because during this timeframe, there were massive chalk deposits.
Here is a depiction of Antartica during the Cretaceous Period. Antartica was covered in forests rather than ice. Fossilized tree trunks and dinosaurs have been excavated there in modern time.
Major Event: The Cretaceous-Paleogene Extinction Event
This extinction event ended the Cretaceous period about 66 million years ago. A plausible theory is that this happened by way of a ginormous asteroid. It was estimated to be 6 miles wide and it struck near present-time Yucatán, Mexico. This is also what formed the Chicxulub crater. The impact was devastating, it formed firestorms, earthquakes, tsunamis, and an almost "nuclear winter" effect, which entails dust entering the atmosphere and blocking sunlight. The event wiped out around 75% of life on Earth. Most dinosaurs were wiped off the planet, but this allowed certain mammals and birds to excel afterward.
Here is a depiction of the asteroid impact.
Most life on Earth was wiped off the planet. Many species were lost and became extinct. Both land animals, such as Tyrannosaurus Rex, and marine life, such as mosasaurs, all left the face of the planet.