Which is not an example of an earth system cycle?
a. seasons
b. tsunamis
c. food web
d. day and night

I think the answer is Tsunami. Unlike the other choices, tsunamis are results of natural disaster. Tsuanamis are often caused by strong seismic movements under the sea bed. They are also after effects of volcanic eruptions under the sea. Tsunamis often occur in the speed of like.

A tsunami is not an earth system cycle. It is rather caused by large displacement of water. Volcanic eruptions, earthquakes, under water fluctutaions lead to huge disturbances in water and lead to its displacement, which causes tsunami.