What is one major geological development during the Mesozoic era?

2. How could you identify the boundary between the Cretaceous and tertiary periods in a rock sample?

Pangaea began to break up into smaller continents, during the Mesozoic Era.

2. Look for a layer of sediment that is full of iridium.

This layer would represent the asteroid that scientists think hit Earth. The layer is the boundary in rock layers between the Cretaceous and Tertiary Periods.