Characteristics of the Mesozoic Click on image for full size (113 Kb) L.Gardiner/Windows to the Universe (fossil images courtesy of AGI Imagebank)

Paleogeography:
At the start of the Mesozoic, the continents were all together in a supercontinent called Pangaea. Throughout the Mesozoic, they pulled apart from one another. A narrow version of the Atlantic Ocean developed as ocean crust was formed at the mid-Atlantic ridge. Continents move due to plate tectonics.

Climate:

• The climate most likely remained warm throughout the Mesozoic. There is no geologic evidence of glaciations and abundant fossil evidence of tropical species have been discovered.
• During the first part of the Cretaceous period (late Mesozoic) there is evidence that the climate warmed greatly and was warmer than it is today. Regional climate variations were negligible. There was little temperature variation between the equator and poles.
• There is strong evidence that relatively sudden climatic cooling occurred at the end of the Mesozoic as a result of either a massive asteroid impact near the Yucatan Peninsula, extensive volcanism in the area that is today India and Pakistan, or the combined effects of both events. The asteroid may even have been large enough to cause the volcanism, or the events may have just happened coincidentally at about the same time. The Sun would have been blocked for some time by debris sent into the atmosphere by the impact and eruptions, cooling the planet.

Evolutionary Events:

• Dinosaurs evolved in the Triassic and became abundant by the middle of the Mesozoic. Dinosaurs were reptiles, however there is evidence that they may have been warm-blooded.
• Birds: During the late Mesozoic, birds most likely evolved from a group of small carnivorous dinosaurs called theropods.
• Plants: Conifer trees evolved at the beginning of the Mesozoic. The first flowering plants evolved during the Cretaceous.
• Mammals evolved during the Mesozoic but there were relatively few species and they were small in size. During the Mesozoic, mammals were most likely food for predatory dinosaurs.
• At the end of the Mesozoic, the Cretaceous Tertiary Mass Extinction occurred. This was the extinction event that killed the dinosaurs (among others). Many of the animals and plants that survived (such as mammals and birds) went on to become very abundant afterward in the Cenozoic. Likely causes of the extinction event include one or more large asteroid impacts, widespread volcanism, and climate change. There is evidence that all three of these happened.
  
  

Characteristics of the Mesozoic Click on image for full size (113 Kb) L.Gardiner/Windows to the Universe (fossil images courtesy of AGI Imagebank)

Paleogeography:
At the start of the Mesozoic, the continents were all joined together forming one large continent called Pangaea. During Mesozoic time, they pulled apart from one another. Continents move due to plate tectonics.

Climate:

• The climate most likely remained warm throughout the Mesozoic. No evidence of glaciations has been found in Mesozoic age rocks and abundant evidence of tropical species has been found in Mesozoic age fossils.
• During the last part of the Mesozoic (called the Cretaceous period) the climate warmed very much. Earth was several degrees warmer than it is today. There was much less variation in temperature between the equator and the poles at this time.
• There is strong evidence that global cooling occurred at the end of the Mesozoic. The cooling may have been caused by either a huge asteroid impact near the Yucatan Peninsula, a large amount of volcanic eruptions in the area that is today India and Pakistan, or by a combination of both the asteroid and volcanoes. The Sun would have been blocked for some time by the debris spewed into the atmosphere.
  

Evolutionary Events:

• Dinosaurs evolved and became abundant! Some were herbivores (eating plants) while others were carnivores (eating meat). Dinosaurs were reptiles, however there is some evidence that they may have been warm-blooded.
• Birds: During the late Mesozoic, birds evolved from a group of small carnivorous dinosaurs.
• Plants: Conifer trees evolved at the beginning of the Mesozoic. The first flowering plants evolved towards the end of the Mesozoic.
• Mammals evolved during the Mesozoic but there were relatively few species and they were small in size. During the Mesozoic, mammals were eaten by carnivorous dinosaurs.
• At the end of the Mesozoic, the Cretaceous-Tertiary Mass Extinction occurred. This was the extinction event that killed the dinosaurs (among others). Many of the animals and plants that survived the extinction event (such as mammals and birds) went on to become very abundant afterward. Likely causes of the extinction event include a large asteroid impact, erupting volcanoes, and climate change. There is evidence that all three of these happened.
  
  
  

Characteristics of the Mesozoic Click on image for full size (113 Kb) L.Gardiner/Windows to the Universe (fossil images courtesy of AGI Imagebank)

Paleogeography:
When the Mesozoic began 248 million years ago, the continents were all joined together. The continents moved very slowly apart during the Mesozoic because of plate tectonics.

Climate:

• Earth was a pretty warm place during the Mesozoic. There were probably no glaciers. Fossils tell us that there were many animals and plants during the Mesozoic that were adapted to warm tropical environments.
• During the last part of the Mesozoic the climate warmed even more! The temperature was not very different between the poles and the equator.
• At the very end of Mesozoic time, the climate likely cooled. The Sun would was probably blocked for some time by the debris spewed into the atmosphere from a huge asteroid impact, a large amount of erupting volcanoes, or by both events.

Events:

• Dinosaurs roamed the planet! Some ate plants. Others ate meat.
• Birds evolved during the late Mesozoic from small meat-eating dinosaurs.
• Mammals evolved during the Mesozoic but there were few species and they were small in size. During the Mesozoic, mammals were likely a food for meat-eating dinosaurs.
• Conifer trees evolved at the beginning of the Mesozoic.
• The first flowering plants evolved towards the end of the Mesozoic.
• At the end of the Mesozoic Period, dinosaurs and many other plants and animals became extinct. Scientists don't know why so many animals and plants disappeared, but we do know that the Earth went through a lot of big changes at this time. These changes affected the Earth's climate, and the animals and plants that could adapt to the new conditions were able to become much more abundant.