什么是run-on sentence

什么是run-on sentence
Obviously,the problem of greenhouse effect is one of the biggest problems that had many big conferences between countries to discussed it today,the movie is just magnifying the effect of this problem in order to lead the reason of this clime disaster more believable.
Moreover,before the main catastrophe happened in THE DAY AFTER TOMORROW there are many small disasters appeared in the movie,like hail and cyclone which could be seen in the normal life,that let the story more closed to people’s experience and give the audience more soul shock than 2012.
In 2012,the communication between the people is not enough,the main action in this story is just run--- run on foot,run by car,run by plane and at last run by a huge ship.
请问这几句有什么问题,老师说我是run-on sentence.但我没看出具体的问题在哪,要怎么修改呢?