Nowadays, as a human develops better and better in technology, economy, healthcare and so on, the number of people being killed by hazard events, which are the extreme natural events in the crust of the earth that pose a threat to life and property, decreases over as human progress. The chart below shows the number of death caused by the geological hazard(drought, floods, extreme weather, extreme temperature, landslides, dry mass movements,wildfires, volcanic activity, and earthquakes) from 1900 to 2019:

The human population has skyrocketed after WW2(World War Two) and reached an incredible 7.7 billion people in 2019[population 2019, n.d]. However, as we look back to around 1940, there were about 2 million people kill by geological hazards when the population was only 2.3 billion[population 1939, n.d], whereas, in 2019, there were only 100 thousand people killed by geological hazards when the population is 7.7 billion. This tells us that the advancement in the technology, economy, and diplomatic system can effectively decrease the effect of geological hazards, from disasters, which kills more than 10 people, and affects more than 100 people, to normal hazard events.

The most common two types of geological hazards are volcanic eruptions and earthquakes. Their magnitude, which measures the amount of energy released from geological hazards, is measured in different scales for different geological hazard activities. The most commonly used scale for an earthquake is the Ritcher scale, which measures the maximum amplitude of the seismic waves. The energy corresponding with the level in the Ritcher scale increases logarithmically. In comparison to earthquakes, the most commonly used scale for volcanic eruptions is VEI (Volcanic Explosive Index). In this case, it measures the amount of material erupted from the volcano. The amount of material(volume) corresponding to the level grows exponentially. 

Theoretically, if all other variables remain unchanged (population density, local economy, etc), the higher magnitude of a geological hazard will be more harmful. Realistically, this is not always the case. There are a lot of variables that are affecting the harmfulness of geological activity. During this essay, I will prove the three variables that are deterministic to the harmfulness of the hazard, through detailed explanations and examples. They are local population density, local economic condition, and location.

On May 18th, 1980, Mount St. Helens(VEI-5) erupted. 57 people were killed by the primary events, which happens immediately(e.g, lahar, pyroclastic flow, etc); and secondary effects(e.g, famine, water shortage, disease, etc ), which occurs after the primary events and are usually caused by the primary effects. In comparison to the eruption of Mount Kelud(VEI-4) on May 19th, 1919, 3000 people were killed nearly instantly by the primary event - pyroclastic flow and house collapsing, with a large number of people killed by the secondary effect, including famine, disease, water shortage and injures. Thousands of houses collapsed due to the weight of volcanic ash falling on them. Considering this is only a VEI level 4 eruption, it is much more harmful than the Mount St Helens’ VEI level 5 eruption as much more people died, and many more properties destroyed. The reasons why Mount St Helens being less harmful than Mount Kalud is mainly because of the local population density, and whether the country is HIC(High-income country) or LIC(Low-income country). Firstly, Mount St Helens erupted in Skamania County which only has 9872 residents in 1980. However, in the Java island(where Mount Kelud erupted), the local population was 35 million back in 1919. Under this condition, even though the death rate is the same, there will be many more deaths on Java island. Therefore, the local population density around Mount Kelud was a lot greater than the population density around Mount St Helens. Lead to a higher number of people of death and a higher impact economically. Secondly, Mount St Helens erupted in 1980 whereas Mount Kelud erupted in 1919. Back in 1919,  Indonesia was a very poor country, with a total GDP of about 68 billion USD. In this case, the government was unable to perform effective rescue and provide necessary resources for victims. Many victims died because of the shortage of resources they need and ended up helpless in the mountain for several days. On the other hand, since the economy was bad, local infrastructures’ quality was terrible at shock resisting, which makes them vulnerable at defending against natural disasters. However, in comparison to the economic condition of Indonesia in 1919, the US was economically developed in 1980, with a total GDP of 2.857 trillion USD. In this case, the US government was able to perform rescue operations immediately after the eruption, so the death caused by the secondary effect was minimized. 

Earthquakes are much more dangerous than volcanos due to their unpredictability. In most cases, scientists can predict the volcanic eruption by measuring the ground shapes as well as light level, temperature, and lava flow at the crater of the volcano. However, earthquakes happen nearly instantaneously and the prognostics are weak. For example, on March 11st, 2011, Japan experienced a massive Ritcher 9.1 earthquake so-called Tohoku earthquake. Unfortunately, this earthquake corresponds with most of the deterministic factors for being the “most harmful disaster.” First of all, the Tohoku earthquake took place in Sanriku, which is one of the heavy population-dense areas in Japan. It was taken place in the shallow sea, the faultline created tsunamis that are 40 meters high. Secondly, the focus was very shallow, with only 24 kilometers deep. Most of the energy arrived at the surface and created seismic waves, that are significantly beyond the shock resistance of the buildings in Japan, so many collapsed and many people were buried alive, suffocated. Thirdly, the key infrastructure that provided the electricity to Tokyo and surrounding cities - Fukushima Daiichi Nuclear Power Plant was destroyed by the tsunami. This lead to an extremely severe nuclear leak accident that is INES-7(International Nuclear Event Scale, INES[7 is the highest]). Hundreds of millions of people were affected by the radioactive substances emitted from the reactor. For a period of time, after the accident happened, the cancer prevalence drastically increased. In the end, 20000 people were killed by the primary event and 368,862 houses were completely or partially destroyed. Therefore, the reason why the Tohoku earthquake was so harmful is that it occurred where it was densely populated, where the key industrial infrastructures were built, and where it can lead to severe primary events like tsunamis, in other cases landslides might be the case. However, Japan as a HIC country was immediately into rescue. With help from other nations like the US and Australia, the secondary’s harmfulness was minimized.