Answer:
Exposure is a matter of how close we are to the hazards. Prevailing winds can bring the ash and toxic fumes from a volcano into the city if the volcano erupts, so it is not only a matter of lava flow that creates exposure.
People build tall masonry People build tall masonry structures near earthquake faults, even though those structures are not stable in quakes. People live near chemical plants because housing is less expensive there and they have been assured that the plants are managed responsibly. People live in the air traffic patterns of airports because they trust that aircraft will not come plummeting out of the sky and land on them. Sometimes, they get that wrong and then people wonder why they accepted those risks.
A hazard is generally contained in a pre-existing condition. Proximity to a volcano, the shallowness of the terrain along the coast, the presence of an earthquake fault are all hazards which present varying degrees of risk at any given time.
Exposure may come as a result of conscious choices that people make, but then again, if the hazards are unknown, then the conscious element in the choice is not present. We do not know about every earthquake fault, nor do we know how often the specific fault will rupture with significant force even if we know it is there.
Human beings are usually willing to assume a certain level of risk in their daily life. We know there are hazards all around us, but we calculate the degree of risk they pose to us and we sometimes get that wrong. People get married even though they know that a large percentage of marriages end in divorce. People live near fault zones because there are so many of them that they are difficult to avoid, so they choose to live where they believe they will have the best opportunities for a good life and they take their chances. Some of the things that create the risks also contribute to the quality of life in that area, such as living on an island on the hurricane track.
