Densification of at-risk urban areas drove most increase in earthquake exposure, shown by the steep slope of the earthquake line above.

Hurricane exposure was also marked by expansion, but trended closer to the national pattern of both densification and expansion of built-up area.

Expansion played a comparatively larger role in the growth of tornado, flood and wildfire exposure in hotspots.

In earthquake, hurricane, tornado and flood hotspots, densification was relatively rapid prior to ~1970.

In wildfire hotspots, densification has steadily increased, suggesting that denser settlements have incurred into wildfire zones but also that low-density development in the wildand-urban interface has tended to fill in over time, an especially worrying pattern.

Similar to the national trends, expansion in tornado, earthquake and flood hotspots decelerated in the 1980s and again in the 2000s.

Hurricane hotspots featured the highest and fastest expansion, as suburbanization of the coastal plain occurred at twice the national rate.

Expansion in wildfire hotstpots was very low until the mid-1970s, and increased thereafter.