This is an example of character versus nature conflict.
In this type of conflict, a natural phenomenon or object (like an animal, a storm, etc.) intervenes in the characters' life in a way that challenges them, that makes them deal with their own weaknesses, thoughts, or emotions. In this case, the characters often find themselves powerless in the face of nature.
Here, we are told that the character named Jess encounters a natural obstacle (a large tree root), and as the result of her fall, she is forced to confront her weakness: "blinking back the tears that threatened to fill her eyes."