Often the biggest danger is the one we can’t see. If we don’t know about something, we can’t prepare for it. Knowledge is half the battle with natural disasters. From surprise earthquakes to toxic waste contamination, here are some of the hazards we had to look under the surface to find.

Toxic Mess Below Dams

Since we have been hearing a lot about American infrastructure, it should come as no surprise that many of our dams are dangerously at risk of failure. What might be surprising is the number of dams that also carry the risk of contamination due to toxic waste in the event of a failure. Even more surprising is how poorly prepared we are for that scenario.

Undark Magazine, a non-profit, independent magazine funded through the Knight Science Journalism Fellowship Program at MIT, recently revealed a shocking 81 dams in 24 states could flood toxic waste sites and contaminate neighboring communities.

Undark’s investigation was initiated by the failure of the Edenville dam in Michigan. After failure of the 97 year old hydroelectric dam, contaminated sediment from a nearby Dow chemical plant were in direct line of the flood. This sediment was mapped and capped by the EPA after it was discovered that Dow had been dumping dioxin-laden waste directly into the nearby river.

Officials became concerned when they realized this toxic waste dump had been designed to handle the river flooding, but not a much larger flood from upstream dams.

Though the Edenville dam situation ended up working out, this could not be the case for future dam failures. Even more concerning, the Undark investigation revealed that this kind of risk is largely unrecognized by any agency. Clearly, the danger exists – someone needs to take responsibility.

The investigation recommends publicly posting the inundation map, which outlines the area expected to be inundated if a failure were to occur. This would allow local officials and even community members to identify and account for toxic hazards.

Blind Fault Lines

Often fault lines create a crack in the Earth’s surface. This makes the faults relatively simple to monitor. Where scientist run into issues is with blind fault lines. These are deeper in the earth and don’t create a crack on the surface.

Because they are harder to monitor, blind fault lines can get ignored – even when they shouldn’t be. One such fault line is the Wilmington fault. Located under the Los Angeles and Long Beach ports, these fault lines were long assumed to be dormant and of little concern. Published in the Bulletin of the Seismological Society of America, a new study suggests we should be more concerned.

By creating a 3D model using various clues, researchers were able to determine that the Wilmington fault is, in fact, active. This is a fault capable of creating earthquakes that are magnitude 6.3 or even higher. The Earth is covered in such faults – many under densely populated cities.

Hopefully, using this new process, scientists can start to monitor the fault lines that had previously been hidden and therefore more dangerous.