Select the statements about the K-T boundary that are true.
- The K-T boundary in Zumaia, Spain is sharp--representing an abrupt change in the marine ecosystem.
- The K-T boundary separates rock layers of the Cretaceous period from those of the Tertiary period.
- The K-T boundary dates to 65 million years ago (when the dinosaurs disappeared).
- The K-T boundary is a layer of debris ranging from large chunks of fractured rock to thin clay deposits and it is found in many different parts of the world. It separates rock layers from the end of the Cretaceous period from those beginning of the Tertiary period. It coincides with an abrupt loss of biodiversity.

The K-T boundary in Zumaia, Spain is sharp--representing an abrupt change in the marine ecosystem.

The K-T boundary separates rock layers of the Cretaceous period from those of the Tertiary period.

The K-T boundary dates to 65 million years ago (when the dinosaurs disappeared)

Explanation:

The Cretaceous-Tertiary (K-T) extinction is the period between the mass extinction of plants and animals about 66million years ago. Based on geological records the    interval between the Cretaceous period and the present day  Tertiary period is  marked by a boundary  is called  K-T boundary.Based on carbon dating this has been estimated  to be 65.5 million years ago.

Evidences has shown that, this boundary must been created by asteroid -Chicxulub  Crater and its impacts must have killed all green plants due to the clouds it produced which blocked sunlight penetrations. This  decimated   the dinosaur population  due to lack of photosynthesis.

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