How did geography impede the movement of ideas or goods?

Certain geographical features have impeded the movement of ideas and goods for centuries. For example the integration of the Americas into the rest of the world system did not occur until the 1500s because the large Atlantic and Pacific Oceans prevented European and Asian access to the Americas. Another example is the isolation that is felt by tribal societies in the Amazon rainforest that have little contact with the outside world because of the habitat that they live in and the difficulty they and others face in reaching this territory. Geographical limits have an enormous impact on the ease and pace of movement of ideas and goods.