Answer:
The first example of these tensions is the conflict between European settlers and Native Americans. As the first group moved westward, the encroached more Native American-held land. This led to a lot of clashes: skirmishes, masaccres, petty fights.
The Indian Removal Act, and the Trail of Tears, which authorized the resettlement of thousands of Native Americans from the southeast to Oklahoma and the rest of the West was a direct result of this clash.
A second example is the conflict between nature and the settlers. This is an ecological conflict. As people moved west, they began to kill american bisons in mass, almost leading to its exctinction. Fur traders and loggers also caused massive animal deaths and losses of forests respectively.