Late Middle Ages: Why is this period often described as one of crisis?

Late Middle Ages:

Why is this period often described as one of crisis? You may want to treat several of the following points:

--Enviromental factors that contributed to the growing economic depression of the 14th century.

--The origins of the Black Death and responses to this pandemic.

--Revolts in Europe (Jacquerie, English Peasants, Ciompi Rebellion)

--Lollards and Hussites.

--Hundred Years War between England and France.

--How medieval Russia was different from that of Europe.