According to a story in The New York Times today, two small African nations - Djibouti and Eritrea - are staged to battle along a disputed border. The opposing forces are within feet or inches of one another. Within the length of a rifle barrel according to the story. To most observers, the contested area is nothing more than desolate sand. However, hostilities there (at the mouth of the Red Sea) could imperil some of the busiest shipping lanes in the world.
This is a very good current day example of how small sparks could produce dramatically disproportionate ramifications far from the site of the crisis. For other similar examples of how marginal events can reshape world affairs and history, read The Power of Incremental Advantage: How Incremental Improvements Produce Dramatically Disproportionate Results.