Closed systems of stratification allow very little change and interaction between social classes. open systems of stratification, on the other hand are more flexible. the open systems of stratification are based on:

They are based on achievement.

Explanation:

Open class systems allow individuals to rise, shift and interact between social classes, they are not bound to stay at their current levels for their whole life. Unlike closed systems in which a person can be born poor, and no matter how much effort he puts he will remain poor until dead, in open systems a person can rise its status through hard work, connections, studies or taking advantage of opportunities.

they encountered severe weather for which they were poorly prepared.

i am confused, what is the question? i can you out if you put it into more depth.