At the beginning of the movie, it shows that there is a drought occuring. Dinosaurs did not have enough to eat, thus, began a journey to the Great Valley, where it was filled with freen food and more cool water.

The "long necks" gave birth to little foot.

Little foot's mother intervened, and managed to defeat him, but suffered many injuries too.
At the same time, there was a clash of continents, which caused a great earthquake that split the lands. Herds were divided, families cut in two.
Littlefoot was separated from his grandparents & Cera was separated from her parents.
Little foot's mother died.
At first, Little foot could not get over the death of his mother. He did not eat, nor think about the Great Valley he must reach.
However, he pulled himself together when he meets an old dinosaur named Rooter.
Along the way, he met a cheerful dinosaur named Ducky, a flier who could not fly named Petrie, Cera, and Spike.

The 5 dinosaurs travelled together to the Great Valley.

Though they were sore-stumped and tired, Little foot kept urging them to go on, even though he had never seen the Great Valley himself.
Doubts began to rise as time past by.

However, Little foot displayed resilience and did not give up. " What if the Great Vallley is just over these rocks?" Little foot was optimistic.
His friends left him for Cera later on, as the path Cera took was much easier.

Little foot still did not give in, and tried to tell them that there were going the wrong way.
Little foot came back to help Cera and the other when they were in trouble.

They finally made it to the Great Valley together, and found their family.